For U Solution

The wheel sensor system on a 1998 Subaru Legacy is directly controlled and monitored by the anti-lock braking system, or ABS, computer. It order to determine which wheels are locking-up, the ABS computer monitors the speed of each wheel individually and compares that speed to the vehicle speed sensor value and the other front wheel. In the event of a wheel lock-up, the ABS computer selectively limits brake pressure until the wheels return to a normal rolling condition. Replacement wheel speed sensors are available for purchase from auto parts stores, Subaru dealerships, and online parts websites.

Instructions

Front Sensor Removal

1

Break the lug nuts loose with a lug nut wrench. Raise the front of the vehicle with a jack and support it with jack stands. Remove the lug nuts and tire.

2

Locate the wheel speed sensor on the inside of the steering knuckle. It is made from black plastic and has a single wire protruding from it that runs up the inside of the strut assembly. Disconnect the sensor connector inside the engine compartment.

3

Remove the bolts holding the sensor harness to the strut assembly with a ratchet and metric socket. Remove the bolts holding the wheel sensor to the knuckle housing with a ratchet and metric socket.

4

Remove the sensor from the housing by gripping the sensor between your thumb and foinger and slowly twisting it back and forth while pulling out of its mounting hole.

Front Sensor Installation

5

Slide the new sensor into its mounting hole on the steering knuckle flange. Insert a feeler gauge between the sensor reluctor wheel and the sensor hole. Press the sensor down into its mounting hole and set the clearance using the feeler gauge. The specified value is 0.9 to 1.4 mm.

6

Install the sensor retaining bolt and tighten it to 17 to 31 foot-pounds using a torque wrench.

7

Feed the sensors wire up to the engine compartment and reconnect it to its primary electrical connector. Position the sensor wire bracket on the strut assembly and reinstall the bracket retaining bolt. Tighten the bolt to 17 to 31 foot-pounds using a torque wrench. Reinstall the tire and lug nuts. Lower the vehicle to the ground and tighten the lug nuts to 65 foot-pounds, plus or minus 7 foot-pounds.

8

Check to make sure that the sensor wire isnt distorted or strangled. Test drive the vehicle to make sure that the sensor operates properly and that no ABS error lights illuminate on the dash board.

Rear Sensor Removal

9

Break the rear lug nuts loose with a lug nut wrench. Raise the rear of the vehicle with a jack and support it with jack stands. Remove the lug nuts and tires. Remove the bolts holding the front seat cushion hinges to the body with a socket and metric ratchet. Lift up the front edge of the seat cushion and detach the rear hooks from back of the seat. Remove the lower seat cushion from the vehicle.

10

Remove the bolts holding the lower-edge of the back cushion to the body. Pull the release strap to release the folding lock on the top of the back cushion. Fold the cushion down toward the body and disengage its retaining hooks. Remove the back cushion from the vehicle. Disconnect the ABS connector thats beneath the rear seat and push the wire through the rubber grommet hole in the body.

11

Slide underneath the rear of the vehicle on a mechanics creeper and remove the bolt holding the rear ABS sensor to the backing plate behind the wheel hub. Remove the bolt holding the sensor wire to the trailing link. Pull the sensor out of the backing plate and remove the sensor assembly from the vehicle.

Rear Sensor Installation

12

Set the sensor wire into position on the trailing link and reinstall the trailing link bolt. Tighten it to 17 to 31 foot-pounds using a torque wrench. Reinstall the ABS sensor into the backing plate and set the gap between the backing plate and the sensor with a feeler gauge; the specified value is 0.7 to 1.2 mm. Tighten the sensors retaining bolt to 17 to 31 foot-pounds with a torque wrench.

13

Feed the ABS wire through the rubber grommet and into the cabin, then reconnect the ABS sensors electrical connector inside the vehicle. Set the seat back cushion into position and attach the lower seat cushion hooks to the mounting holes. Fold the seat back cushion up until it latches into position, then reinstall the seat back cushion retaining bolts.

14

Set the lower seat cushion into position and engage the rear latches with the retaining hooks on the back of the seat. Fold the seat down and reinstall the seats retaining bolts. Reinstall the tires and torque the lug nuts to lug nuts to 65 foot-pounds, plus or minus 7 foot-pounds. Lower the vehicle back to the ground, then test drive it to ensure that the sensors operate properly.

The crankshaft position sensor is an electronic component designed to fine-tune the timing of a vehicles engine. The sensor works with the vehicles on-board computer to ensure the vehicle runs at optimal performance.

Purpose

The crankshaft position sensor monitors the position and speed of the crankshaft to control the ignition system timing. The component aids in variable valve timing by monitoring the movement between the vehicles pistons, valves and the engine, noting the engines revolutions per minute.

Function

Made from magnets and an inductive coil, the crank position sensor is positioned next to the crankshaft. The crankshaft has several pins spaced an equal distance apart which is read and calculated by the magnets within the sensor as the crankshaft spins.

Location

These sensors are located in the lower front of the engine block either directly next to the crankshaft, within the main crank pulley or the flywheel. The crankshaft position sensor can be identified as a long, thin, black cord.

The 2002 Hyundai Santa Fe is equipped with two oxygen (O2) sensors within the exhaust system. Designed to control the fuel consumption based on the oxygen in your cars exhaust, the oxygen sensors thread into the exhaust manifold and catalytic converter of your Santa Fe. When the cars fuel economy begins to decrease significantly, you may need to replace the oxygen sensors. Buy replacement sensors from an auto parts retailer and change them at home in minutes.

Instructions

1

Raise the Santa Fe with a jack and support it on a set of jack stands. Locate the oxygen (O2) sensors along the exhaust system.

2

Pull the electrical connection from the top of the oxygen sensor. Remove the existing sensor with an oxygen sensor socket and ratchet.

3

Thread the new oxygen sensor into place by hand to avoid the risk of cross threading and damaging the sensor. Torque the sensor to 40 pound-feet with your torque wrench. Push the electrical connector back into place until it clicks.

4

Repeat the process on the second sensor, if needed. Raise the car slightly with the jack to remove the jack stands. Lower the car to the ground.

The 1995 Chevrolet Corsica depends on an oxygen sensor within the exhaust system to monitor the amount of oxygen in the exhaust. The oxygen content of the exhaust determines how much fuel the car uses to keep the engine running. If the sensor fails, your car may start to use a lot more fuel than needed. To save this needless fuel expense, buy a replacement sensor from an auto-parts store and change it at home. The location of the O2 sensor will vary, depending on the engine in your Corsica.

Instructions

1

Start the engine and allow it to warm up, heating up the exhaust system. Turn the engine off before removing the sensor. Raise the Corsica with a jack. Place a set of jack stands beneath the car to support it.

2

Locate the oxygen sensor from beneath the car. The sensor threads into the rear of the manifold or the side of the exhaust pipe. Pull the wiring harness connector apart on the end of the sensor.

3

Remove the oxygen sensor from the Corsica with an oxygen sensor socket and ratchet. Place the new sensor into the mounting area and thread it by hand until it no longer turns easily. Tighten it with an oxygen sensor socket and ratchet.

4

Torque the sensor to 30 foot-pounds with your torque wrench. Connect the wiring harness by pressing the connectors together.

5

Raise the car with a jack to remove the jack stands. Return the car to the ground.

The 3.3L Dodge engine is a front wheel drive V6 engine that was first introduced in 1990 for use in Dodge mini-vans and front wheel drive cars. The oxygen sensor on these vehicles is a small sensor located in the exhaust manifold. The oxygen sensor measures the amount of unburned oxygen in the exhaust. This measurement allows the engine computer to adjust the air fuel ratio for optimal efficiency.

Instructions

Removing the Oxygen Sensor

1

Disconnect the ground cable from the negative battery terminal by loosening the retaining bolt with a wrench. Pull the clamp off the terminal.

2

Raise the front of the vehicle using an automotive jack. Support with jack stands placed underneath the front frame.

3

Locate the oxygen sensor. It will be screwed into the intake manifold near the flange that connects the exhaust manifold to the head pipe.

4

Separate the wiring connector on the oxygen sensor from the engine wiring harness, by pressing in both tabs with you hands. Then pull the two sides of the connector apart.

5

Unscrew the oxygen sensor from the exhaust manifold using an oxygen sensor removal socket and breaker bar. The oxygen sensor socket features a slot along the side to facilitate removing the socket without damaging the wiring harness.

Installing the Oxygen Sensor

6

Screw the new oxygen sensor into the exhaust manifold, using the oxygen sensor socket.

7

Plug the oxygen sensor wiring connector onto the engine wiring harness connector using your hand.

8

Lower the vehicle.

9

Reconnect the ground cable to the negative battery terminal by sliding the clamp over the terminal. Tighten the retaining bolt using a wrench.

A fuel-injected engine uses many different sensors to determine how to make your engine run properly. The 1987 and newer GM trucks use one or more oxygen sensors located along the exhaust. Theyre not difficult to replace, but they can take some elbow grease and some basic safety equipment to do properly.

Instructions

Lift the Truck

1

First, make sure the vehicle is turned off, has cooled down for a few hours and the emergency brake is set. Using a jack, lift the front of the truck so that the front tires are off the ground. A good jack point is the front crossmember, or alternatively, the sides of the frame below the doors.

2

With the truck properly supported, slide underneath the vehicle and look for the O2 sensor. Depending on the year of the truck, there will be just one sensor located on the passenger side near the transmission, or several sensors on the later models, located both before and after the catalytic converters. Theyre easy to spot, as they stick out about 2 inches from the exhaust tubing and have two wires coming out from the body.

3

Unplug the harness that connects the O2 sensor to the stock wiring. If the clip that holds the harness together is difficult to disconnect, use a small flathead screwdriver to pop it free.

4

Using an O2 sensor socket or an appropriately sized wrench, loosen and remove the old O2 sensor. It unthreads like any other bolt would, going to the left to loosen. Should the sensor be stuck in the threads, loosen them with some WD-40 or similar product. Should the sensor still not come loose, the bung can be cut out of the exhaust, but it will have to be welded back into place by a professional, and should only be done as a last resort.

5

Before installing the replacement O2 sensor, put some anti-seize compound around the threaded area of the sensor. This will help you the next time you have to replace the sensor, as the heat of the exhaust wont cause the threads to seize up on you.

6

To reinstall, thread the O2 sensor into the bung on the exhaust, reconnect the wiring and lower the truck off of the jackstands.

The oxygen sensor in a car is now an integral part of the exhaust system. Although it has been around for many years--since the implementation of On-Board-Diagnostics II in 1996--the amount of oxygen sensors per car has doubled. Finding them for replacement is now much trickier.

Location

The oxygen sensors are located directly in the exhaust system, usually by portholes that the sensor screws into on the exhaust pipes--and in some cases, on the exhaust manifold. The exterior portion of the sensor provides a wire and plug that plugs the harness into the ECU and transmits the voltage for monitoring.

History

Designed in the 1960s by a Robert Bosch, the oxygen sensor in a car made its first introduction in the late 1970s on a Volvo that also introduced the 3-way-catalyst system. By 1981, to reduce emissions, all vehicles were being manufactured with catalytic converters.

Function

The function of the oxygen sensor (also known as the Lambda sensor) is to monitor the amount of fuel-to-air mix in the combustible engine of a vehicle. The sensor transmits voltage and the engine management computer (ECU) monitors the ratio. There is an ideal ratio--when a sensor fails or there is an internal problem with the engine, more pollutants emit from the exhaust.

Types

The older sensors were "unheated" sensors. Since they do not transmit voltage until their internal temperature reaches 600 degrees Fahrenheit or more, this allows a period of time in between the ECU being able to monitor the sensor. "Heated" sensors are common today, have extra wires for the heating element and assist in heating the sensor more rapidly.

Considerations

If replacing an oxygen sensor, a direct-fit replacement is far superior to the "universal" sensor which would require cutting, identifying and splicing the wires of the sensor. The direct-fit sensor provides the necessary wires and plug to fit the plug of the wire harness easily.

The knock sensor in your car detects a low-frequency engine knock and sends an electrical signal to other parts of your car. This makes knock sensors vital to proper engine timing, fuel efficiency and power.

Preparation

Varying in location on different vehicles, knock sensors are often found in the engine block, intake manifold or the cylinder head. While specific tool sizes may also differ by engine, youll generally need a ratchet with a socket fitting the knock sensors nut. Before beginning, drain the engine coolant.

Replacement

After caully removing the electrical connectors cover from the sensor, use the ratchet and socket to unscrew and remove the knock sensor. Evenly thread the new knock sensor into the hole and tighten it. Innova Electronics Corporation instructs to tighten the nut to the engine manufacturers inch-pound torque recommendation then reconnect the electrical connector.

After the Replacement

After replacing the knock sensor, youll replace the engine coolant and ensure that its full. Next, you should start the engine and visually inspect for coolant leaks, then test drive the vehicle to ensure proper working order. If the "Check Engine" light was on, it should turn off after replacing the knock sensor unless theres another engine problem. Continue to inspect for coolant leaks over the next few days, just to be sure.

The 1999 Saturn SL features a four-cylinder, 1.9-liter engine with two oxygen sensors that monitor the exhaust emissions. One is located directly into the manifold and can be accessed and replaced from the engine compartment. The other is located just behind the catalytic converter in the converter/front flex-pipe assembly. Because of the easier access to the "upstream" sensor (in the manifold), the sensor is actually easier to replace than the "downstream" sensor (near the converter), unlike the case with many other vehicles, which require you to get under the vehicle to replace any oxygen sensor.

Instructions

Downstream Sensor

1

Place a wheel chock behind one of the rear tires and then apply the parking brake to the Saturn SL.

2

Lift the drivers-side front quarter of the vehicle with a jack high enough to place a jack stand under the front frame rail (place it up in front of the converter to keep it out of the way of the work space). Repeat the procedure for the passenger-side front quarter to elevate the front axle.

3

Put on safety glasses and crawl under the front-center of the Saturn to the location of the steering rack just above the catalytic converter shell. The downstream sensor wire will be visible. The wire runs along the drivers-side edge of the converters heat shield and its plug connection is fastened up near the steering rack. Reach up to lift the wire harness plug clip lock while pulling the sensor wire mating plug free.

4

Snip the zip tie retainers of the wire down the length of the sensor wire. Repositioning from under the front-center over to the drivers side may help you reach the lower downstream zip ties to the sensor location.

5

Slide the heat-resistant cover off the oxygen sensor wire.

6

Align the sensor wire into the slot on the side of the oxygen sensor socket. Place the socket firmly onto the oxygen sensor. The small heat shield for the sensor makes it a tight fit.

7

Attach the ratchet to the socket and turn the sensor counterclockwise to remove it. It may be stubborn at first, but some leverage and ingenuity will pay off.

8

Hand-thread the new sensor into the oxygen sensor port. Tighten the sensor snugly with the ratchet and socket, again aligning the wire into the slot of the socket. Do not over-tighten or the threads of the sensor may strip.

9

Slide the original heat-resistant wire cover over the plug connection of the new sensor and feed it down to the sensor.

10

Plug the sensor back into the wire harness mating plug.

11

Zip-tie the wire to the heat shield, so it does not droop, before lowering the Saturn back to the ground.

Upstream Sensor

12

Open the hood and locate the upstream sensor. Its clearly visible in the front-center of the engine placed at the top of the manifold.

13

Disconnect the sensor harness plug from the wire harness mating plug located (and affixed) to the fan shroud. Lift the lock on the wire harness side of the plug and pull the socket wire plug away.

14

Place the socket onto the sensor, aligning the single wire into the slot of the socket.

15

Place the ratchet on the socket and turn counterclockwise to remove.

16

Place the new sensor into the sensor port, hand-tighten and the snugly tighten with the ratchet and socket before plugging the sensor into the wire harness mating plug. Close the hood.

The oxygen sensor monitors the fuel-to-air ratio in the spent exhaust near or on the manifold. Since the integration of OBD II (on-board diagnostics) in 1996, the amount of oxygen sensors on vehicles has doubled. Upstream sensors still monitor the exhaust from the manifold; downstream sensors now monitor the catalyst efficiency near the catalytic converters. While replacing some oxygen sensors is a simple task, vehicle designs can frustrate the most seasoned mechanics when it comes to replacing them due to lack of access. Tool companies advance along with technology. Luckily, theres always the right tool for the job.

The Environment of the Oxygen Sensor

Most oxygen sensors screw into portholes or bungs in the exhaust system. Due to extreme heat from the exhaust of the combustion engine, the pipes of the exhaust system heat up when operating and then cool down after the vehicle is shut off. This creates an unfriendly environment for the metals of the exhaust pipe and the threads of the oxygen sensor. Even sensors that are easily accessible can provide a high degree of difficulty when trying to be unscrewed from the exhaust pipe.

Tools and Taps

Rest assured that there is the right tool to remove the most challengingly accessible oxygen sensor. While many offer easy access, todays tools will offer you a variety of choices as well as combining other common tools in order to successfully remove oxygen sensors.

Oxygen sensor wrench with flex heads are now available. Oxygen sensor sockets with slotted edges are also quite popular. Wrenches that fit onto the hex-head of the sensor--most commonly a 22-mm or a 7/8-inch drive--accompanied with a square drive in the wrench to accommodate a ratchet extension can be used. Swivels are another friendly tool for access-challenged sensors. And in the easiest ones to remove, a box-end wrench can even be used.

Always unplug the wire harness of the sensor before attempting to remove it.

A Little Heat Might Help

So now, youve found the right tool or the right combination, youve unplugged the wire and placed it through the wrench or into the slot of the socket and the sensor is still stuck. While some suggest heating up the engine by running it will help, the fact is, under this procedure, the heat expands both the exhaust pipe and the sensor threads. Penetrating lubricant in liberal doses may help in this manner, but if you have a small propane or oxyacetylene torch, you can also heat the edges of the bung on the exhaust pipe. This will expand the pipe and bung without greatly affecting the sensor. A little heat will go a long way when removing stubborn sensors.

Its also a good idea to allow the pipe to cool down and then chase or tap the bung with an O2 sensor thread tap or chaser. Commonly an 18-mm diameter with a 1.5-mm thread pitch is used, but check the sensor threads and diameter at the parts store when you buy it to make sure. This will make threading the new sensor easier. Since the threads of oxygen sensors are much weaker than the bung, you can easily damage or cross-thread a new sensor trying to install it without chasing the threads of the bung. Apply a little anti-seize lubricant on the threads of the sensor--being caul not to get any on the head of the sensor--before tightening; although many quality aftermarket sensors will provide some anti-seize compound on the threads for you already.

The oxygen sensor in your 2001 Toyota Tundra may one day go bad and need replacement. The oxygen (O2) sensor is responsible for regulating the oxygen and fuel ratio in your vehicle, contributing to the efficiency of gas usage. If the oxygen sensor goes bad, your Tundra may run poorly and get poor gas mileage. Knowing how to replace it yourself can save you money.

Instructions

Instructions

1

Locate the oxygen sensor on the pre-catalytic converter. This is located near the right-front wheel well of your Tundra.

2

Detach the large air intake pipe that is connected to the air box going to the rear turbo. Also remove the two smaller air pipes connected to the air box running to the blow off. This will give you access to reach the sensor. Soak the oxygen sensor in penetrating oil (WD-40 or similar) to loosen it for easier removal.

3

Use the 7/8-inch wrench to remove the old oxygen sensor. Find the stock sensor wire near the engine lift loop by the firewall. Splice the stock sensor wire and connect it with the wires to the new oxygen sensor using crimp connectors.

4

Apply some of the anti-seize paste to the threads of the new sensor. Be caul not to get any of the paste on the sensor itself or it will ruin it. This will make the oxygen sensor easier to remove the next time.

5

Screw the new sensor in by hand. Fully tighten it with the wrench so it can not be loosened by hand. Reattach the air pipes again.

The oxygen (or O2) sensor on your Toyota helps balance the engines fuel-to-air ratio. A faulty O2 sensor can cause your engine light to come on. It might also prevent the vehicle from starting. Your Toyota is equipped with two O2 sensors. They are located underneath the vehicle on the exhaust pipe, with one on either side of the catalytic converter.

Instructions

1

Set the emergency brake.

2

Jack up the front end of your Toyota. Put the jack stands in place.

3

Slide under the vehicle with the socket set and locate the O2 sensor you will be replacing. Sensor 1 is located on the exhaust pipe, on the left hand side of the catalytic converter. Sensor 2 is located on the right hand side of the catalytic converter closest to the vehicles rear end.

4

Loosen the two mounting bolts that hold the sensor to the exhaust pipe with your socket set.

5

Unplug the sensor from its socket by squeezing in the two safety tabs on the sides of the socket and pulling the sensor free.

6

Plug in the new O2 sensor. Re-mount it to the exhaust pipe with the mounting bolts.

7

Remove the jack stands and lower your Toyota.

From the speedometer to the cruise control to the transmission, the data collected by speed sensors affects the operation of multiple systems functioning within your car. In fact, many systems rely on these sensors input to operate. Speed sensors measure the speed of the transmission/transaxle output of the wheel, then send a signal carrying this data to your cars operating systems.

VAPS

The variable-assisted power steering (VAPS) system in your vehicle utilizes speed sensors so you can navigate parking lots, school zones and other low-speed areas with ease. The VAPS system controls and adjusts the cars power steering pressures. The speed sensors send data on speeds to the VAPS that allows the system to control and adjust power steering pressures. This regulation of power steering pressures allows the system to help you decelerate easier, which in turns helps you drive in low-speed areas.

ABS

The speed sensors used by the anti-lock brake system (ABS) of your vehicle let the ABS know when a wheel locks up and when to discharge pressure from that wheel so you can continue to steer the car. Depending on the brand of vehicle you own, the ABS may utilize sensor from transmission/transaxle, wheel, or a combination of both sensors.

Speedometer

Unsurprisingly, speed sensors also help your cars speedometer operate. The instrument cluster (IC) and hybrid electric cluster (HEC) modules translate the data from the speed sensor into a reading on your speedometer.

Advanced Air Suspension System

If your vehicle employs an advanced air suspension system, the speed sensors may also help determine how high your car rides. The height of your car affects how your car handles at high speeds. The lower your car sits, the better it will handle when youre driving fast.

Transmission

Speed sensor input data to your transmission as well. The information they gather tells the transmission how to shift as you change speeds.

Cruise Control System

The information from the speed sensors allows the cruise control system of your car to maintain a steady speed, accelerate and decelerate without you having to touch the gas pedal or brake pedal.

EEC

The electronic engine control (EEC) system uses the signals from speed sensors to adjust engine functions due to fluctuations in speed. It also uses input from the sensors to begin diagnostic procedures.

You might need to replace the oxygen sensors on your 2002 Hyundai Sonata if you notice your fuel consumption increasing, or if your "check engine" light illuminates. The oxygen sensor measures the amount of oxygen being expelled through the exhaust and adjusts the fuel necessary to meet certain oxygen levels. You have two sensors, one in the manifold and one inline with the catalytic converter. Remove both in the same manner.

Instructions

1

Locate the oxygen sensor in the exhaust manifold or the exhaust pipe next to the catalytic converter. It resembles a spark plug and has one thin wire extending from it. Use the replacement sensor for a visual aid.

2

Push in on the lock on the wire harness at the top of the sensor. Pull the wire off.

3

Remove the sensor with a deep well socket or wrench. Due to the extreme heat generated in the manifold and exhaust pipe, it is common for the sensor to become stuck. If necessary, use spray-on rust breaker such as liquid wrench to aid in the removal process.

4

Place a small amount of anti-seize compound on the threads of the new oxygen sensor and thread the sensor back into the manifold or tail pipe.

5

Push the connector of the wire back onto the oxygen sensor.

2000 model year Nissan Xterras came equipped with two engine choices: A 2.4-liter four cylinder engine and a 3.3-liter six cylinder engine. Both of these engines contain a crankshaft position sensor which electromagnetically monitors the position of the crankshaft. The ECM reads the signals from the crankshaft sensor and fires the spark plugs based on this information. If the crankshaft sensor fails, the ECM does not know when to fire the plugs, resulting in a dead engine. Because the crankshaft position sensor contains an electrical coil, its condition can be determined by measuring the resistance across its terminal pins with a digital multimeter. The procedure for checking the crankshaft position sensor is identical for both engine variations.

Instructions

1

Shut off the engine, open the hood, and let the engine cool down for one to two hours to avoid any burns.

2

Shine a work light on the back side of the engine block, where the engine meets the transmission bell housing. Locate the crankshaft position sensor. It is set into the engine block near the upper left corner of the transmission bell housing. Disconnect the sensors electrical connector and remove the bolt holding the sensor to the block with a ratchet and metric socket.

3

Remove the sensor by pulling on it while twisting it back and forth. Once the sensor pops out, dry it with a clean shop rag. Inspect the sensor for cracks or chipping. Replace the sensor if you find any crack or chips.

4

Set your digital multimeter to Ohms or resistance. Use the two multimeter probes to measure resistance across the crankshaft position sensor terminals. The specified value is 166.5 to 203.5 Ohms at 68 degrees Fahrenheit. If the sensors resistance falls outside this value then it is faulty and needs to be replaced.

5

Visually inspect the crankshaft position sensors wiring harness on the vehicle. Look for bare spots on the wires and chips or cracks on the plastic connector. Insert a small flat-head screwdriver into the metal connector pins and wiggle the screwdriver back and forth. The pins should remain in position and should not be loose. Inspect the pins for excess corrosion or damage. If any of these conditions exist, replace the crankshaft position sensors wiring harness.

6

Turn on the ignition and set your digital multimeter to "DC Volts." Probe the light blue wire on the crankshaft position sensors electrical connector with the red multimeter probe. Ground the black multimeter probe and look at the voltage reading. The reading should be between 2 and 12-volts. If the value is out of this range then the sensor is not receiving power, and youll need to troubleshoot the engine wiring harness. Connect a test lamp to the positive battery terminal and probe the ground side of the crankshaft position sensor. If the test lamp doesnt illuminate, then the ground is bad and youll need to troubleshoot the engine wiring harness.

With ever-tightening environmental regulations, auto makers have created vehicles with less tolerance for wastes in the exhaust system. Unfortunately, the O2 sensor has become known for incredibly high failure rates, driving many owners to seek do-it-yourself replacement options.

Function

To run optimally, your car needs a careful mix of air and fuel. The O2 sensor measures the amount of oxygen (known in chemistry as O2) in the exhaust; if it has too much, it signals the injection system to cut back the available air supply. Most cars have two or more, in pairs, used to determine the efficiency of a specific component, such as the catalytic converter.

Location

The specific location of the O2 sensor varies a bit by manufacturer and by model of the vehicle in question. If you understand basic automobile anatomy, however, you will always find the "exhaust" sensor by tracing the exit of the catalytic converter along the exhaust pipe. If you follow it carefully, you will see something that looks like a spark plug screwed directly into the pipe -- this structure is your exhaust O2 sensor.

Safety Considerations

You would not have bothered finding the sensor without a reason; before you remove it, however, take precautions. Always disconnect the battery from the electrical system, and allow sufficient time for your exhaust system to cool off after operations. Finally, use a penetrating oil on the area on and around the sensor, and allow it to soak for at least 15 minutes.

The Mercedes Benz ML320 uses four oxygen sensors in the exhaust system. Before replacing all of them, have the dealer or other service center scan the computer for codes that will indicate which sensor is failing. The sensors lock into the exhaust system just before and after the catalytic converters under the car. Replacement sensors are available at most auto parts stores and through your Mercedes dealer. Bosch manufactures the OEM sensors as well as replacement sensors for the Mercedes ML320.

Instructions

1

Raise the front of your ML320 with a jack then position a set of jack stands under the frame to support the car. Lower the jack until the car is resting securely on the jack stands. Remove the jack from under the car.

2

Position yourself under the car just behind the front wheels. Locate the catalytic converters in the exhaust system then select the sensor you need to change. There are two in front of the converters and two behind them.

3

Follow the wiring harness coming out of the top of the O2 sensor to the connector where the sensor wires and the cars wiring harness join. Release the locking tab and separate the connectors.

4

Place an O2 sensor socket over the sensor then turn it counterclockwise with a ratchet, removing the sensor from the exhaust pipe. Discard the old sensor and install a new sensor in the threaded hole on the exhaust, tightening it with the O2 sensor socket and ratchet.

5

Plug the wiring harness connector from the O2 sensor into the connector on the cars wiring harness, making sure the locking tab engages the connector. Repeat these steps on any of the other O2 sensors that require replacement.

6

Raise the front of the car off the jack stands with the jack then remove the jack stands from under the car. Lower the jack and set the car on the ground.

The manifold absolute pressure, or MAP, sensor plays a vital role in keeping an engine operating at peak efficiency. Without a properly functioning MAP sensor, an automobile engine will run poorly or may fail to run at all.

Purpose

The MAP sensor measures air pressure inside an automobiles intake manifold. The level of air pressure depends on how hard the engine is working. Under heavier loads, the engine uses more air, which reduces the pressure in the manifold. The engines computer uses the amount of pressure measured by the sensor to adjust the fuel injection and ignition timing.

Signs of Problems

A defective MAP sensor results in poor engine performance. Typical symptoms of MAP sensor failure include rough idle, stalling, spark plug "knocking" and an increase in fuel consumption. Auto-parts stores sell diagnostic scan tools, which determine if a MAP sensors working properly.

Replacement

A defective MAP sensor requires replacement. Manufacturers calibrate MAP sensors for specific models and engines, so car owners should note the type needed before purchase. When replacing the MAP sensor, drivers should also inspect the vacuum hose attached to it, and replace a hose showing cracks or other damage.

The V6 4.3-liter engine of the 2002 Chevrolet Blazer has four oxygen sensors that monitor the fuel-to-air ratio and the catalyst efficiency. Locating the correct oxygen sensor or sensors to replace may be more challenging than actually replacing them. Keep in mind that the bank one sensor is on the same side as the number one cylinder, and the two sensors one (1) are on the front pipe just below the manifold. The two rear sensors are on the passenger side of the SUV; one placed in front of the catalytic converter and one directly behind it. These are referred to as sensors two (2).

Instructions

1

Drive the 2002 Chevrolet Blazer up onto two car ramps, and then apply the parking brake.

2

Place a wheel block behind one of the rear tires.

3

Put the safety glasses on, and crawl underneath the Blazer with the remaining items.

4

Locate the oxygen sensor(s) you intend to replace. The two front ones are located in the front Y-pipe of the exhaust system towards the front of the engine. There is one per side of the Y-pipe. The other two are located before and after the catalytic converter (which is just behind the Y-pipe towards the center of the vehicle on the passenger side).

5

Spray the threads of the oxygen sensor with penetrating lubricant, and allow it to soak in for a few minutes.

6

Follow the wire harness from the oxygen sensor to the plug connection. Use a small forked pry tool to unseat the retaining tab of the plug connection from the frame or undercarriage of the SUV. Disconnect the wire harness plug.

7

Place the plug of the sensor through the box-end side of the 22-mm or 7/8-inch wrench, and then place the wrench onto the hex-headed portion of the sensor.

8

Turn the sensor counterclockwise using the wrench. A quick jerking motion of the wrench should loosen the sensor effectively, but if necessary, start the engine for a couple of minutes to warm up the exhaust system and expand the binding metals of the pipe and sensor. Be careful that it will not heat up the front Y-pipe sensors because they can become hot enough to burn you.

9

Thread the new replacement sensor into the exhaust port by hand as far as it will allow. Tighten the sensor to 30-foot pounds with a torquing hand wrench. Do not over-tighten the sensor, or you will damage the threads.

10

Reconnect the wire harness of the replacement sensor to the plug connection, and then push the retaining tab back into its respective hole in the frame or undercarriage.

Automotive O2 sensors determine in real time if the air fuel ratio of your vehicles engine is lean or rich. They make electronic fuel injections and emission control possible. Sensors typically last from 30,000 miles to more than 100,000 miles. Driving with a bad O2 sensor is like avoiding going to the dentist. You will cause damage to your car, just as you would cause damage to your teeth by avoiding the dentist. The only issue is how much damage you are willing to endure before you replace your O2 sensor.

Instructions

1

Drive the speed limit at all times. Do not speed. Your gas mileage and catalytic converter are already in jeopardy due to the bad O2 sensor. The harder you drive, the more damage you will cause to your catalytic converter.

2

Accelerate slowly. Slamming on the gas to achieve quick acceleration will exacerbate any damage being done to your vehicle.

3

Brake often. Again, the slower you drive, the better. Leave at least three to five seconds of time between yourself and the vehicle in front of you.

4

Plan out your trips before you leave your home. If you plan ahead of time, you will avoid backtracking and any unnecessary driving.

5

Limit driving as much as possible. If you can wait to mail that letter to your grandma, wait. If you can walk to any spots you need to go to, do so. Walking is good exercise and it will limit wear and tear on your car.