Car Computers and Sensors

Car computers and sensors are modern tools that make driving easier. A car’s built-in sensors provide the driver with information on any abnormal signs while a car’s computer controls the car’s performance.

10,645 Questions
Car Computers and Sensors
Car Starting Problems
Starters and Ignition Systems
Ford F-150

How do you test an ignition coil?

How to test an ignition coil

This testing procedure is valid for just about any automotive coil. Using an ohmmeter, check the resistance between the side terminals of the coil. Do this with all of the wires to the coil disconnected.

You should see 0.75 to 0.81 ohm of resistance. Then check the resistance between either side terminal and the center high tension terminal. The reading should be 10,000 to 11,000 ohms. Any significant deviation from these numbers would indicate that the coil could be defective.


You can also rest an ignition coil by using a volt meter.There should be a little over 12 volts pulse, or a dip and peak in the meter needle, rather than a steady 12 volts, at the output, while cranking the engine.


Be careful about these answers. My voltmeter has a 9 volt battery installed. An ignition coil can produce 20 kV - that is twenty thousand volts! - at 100 mW, now that would bother me a bit.

So now, how can we check this coil safely? Well, start by shorting the output (the high tension terminal) and check the primary winding for continuity. On a normal meter 0.75 ohms might be very hard to read but, if you use a 1.5 flashlight bulb and battery in series with it, if the bulb lights, the primary winding is probably ok. (Unless its insulation has got fried by a fault called a "shorted turn", in which case the flashlight bulb will still light up but the ignition coil still won't work...)

The secondary, high tension, winding of the coil can be checked by shorting it with a high resistance load having a tap to form a 1000:1 split ratio, so you can use your meter to check for an output voltage of around 20 volts when a small 1.25 volt battery is connected and disconnected to the primary.

The actual output voltage should let you work out the turns ratio between primary and secondary of the coil. maybe Note: to see the output voltage for a longer time, add a diode and capacitor onto voltage divider tap.
I need to know how to check a coil on a Honda accord 94

Auto Parts and Repairs
Car Computers and Sensors
Ford Crown Victoria

Can bad mass air flow sensor cause engine misfire?

it will feel like a misfire but should not cause a single cylinder misfire code. a bad maf ( mass air flow ) would and can set random multiple misfire codes, lean bank 1 and 2 just like a clogged fuel filter or restricted exhaust ( cat )

Car Computers and Sensors
Nissan Frontier

Where is the speed sensor located on a 1996 or newer Taurus - Mercury Sable?

  • Transmission Range Sensor - aka Neutral safety / start switch.

    See "Related Questions" below

  • Vehicle Speed Sensor - aka Output Shaft Speed Sensor
  • PICTURES - (yes, photos!) - See "Related Links" below
Symptoms - (See "Related Links")Symptoms (Each bullet point is a symptom that doesn't necessarily happen at the same time):
  • Speedometer inaccurate
  • Speedometer needle not working
  • Speedometer needle jumping around
  • Bad/harsh/no shifting
  • Car not shifting out of first or hold out first a lot longer
  • Cruise control not working correctly (speed jumps up and down)
  • Cruise control not working at all
  • No Overdrive

The vehicle speed sensor is located on the rear, left hand side of the engine as you stand in front of the car looking at the motor. When you look at the back of the engine , under the exhaust manifold , there is a small heat shield that you can pull off [it is spring clipped on the back, so you can pull it off without damaging it] and there it is.

It's hard to see the sensor from the left side ,I had to place a light by the exhaust , then look at it from the right hand side of the car. I removed it by working from the right side stretching over, the only way I could see it and get to it.

There are 2 types of sensors available depending on your transmission. I bought both ,1 was special order, and both appeared wrong, till someone told me I had to reuse the gear from the old sensor and place it on the new one. Came off easily by removal of clip. One of the new sensors already had a gear, but it was too large [special order one] the other had no gear and was the one I needed and had to switch gear from old sensor to new


if its the same as a 98, then with the hood up and your looking towards the rear of the car, its on the left side of the engine, at the back, look way down over the exhaust manifold and you will see a two wires in an insulated sleeve disappearing into a rectangular heat shield, pull on the heat shield and it will come off and slide up the wires and voila there it is. mine was a swine to get out, the top part of the vss sensor came off, i had to thread a 5/16 lag bolt into the thing and pound it out with a slide hammer gear puller, but the shop wanted $400 to replace it.. i was successful and went to dinner with the savings lol


The trick is to snake your arm down the back, adjacent to the manifold pipe, and unplug the wiring harness. I used a 10mm socket to unscrew the bolt that holds the sensor in place. Once the screw was out it was easy to pull the sensor out and rush to Auto Zone and get a new one. Reverse the process in putting the sensor in(20 min flat), test drove that bad boy and it works like a charm. All done it cost me $20 that's a far cry from $150 to $250 to have it done at a garage. Yoah! I'm a happy camper.

Later, Will


When standing in front of the facing the motor, the speed sensor is on the left hand, back side of the motor in the rack & pinion. Just unplug the sensor and get a strong grip on the sensor and pull it straight up and out. To put the new one in, just push it in the hole where the old one came out until it snaps in over the o-ring. I had to change mine about 2 years ago and that's all there is to it. I hope this will help!!! Good Luck!!


The speed sensor is on the passenger side top of the transmission! It's not on the rack and pinion! I'm a student at Albany Technical College in the automotive technology class and I recently had to replace the one on my Grandmothers car. The best way I found to do it was remove the passenger side tire and then remove the passenger side motor mount and...voila! It's right on top of the transmission and the 10mm bolt is on the drivers it is a little tricky to get to! You take the bolt out and pull the old one out...and put the new one in and reverse the process! it's time consuming but...thats the easiest way I could find to do it! Hope this helps anyone else that has to replace this!


Remember that there is one nut (10mm) that needs to be removed before the sensor will pull out. The sensor might (should) have a silver heatshield around it, so it might blend in with the surroundings.


I just did the VSS on wife's '96 Taurus. A much easier way is to remove the air tube from the air cleaner to the throttle body, disconnect the charge air temp and the MAF sensor and set it out of the way. Put the transmission in the lowest position to move the trans lever out of the way. It is a straight shot from the drivers side. Pull the sensor up from the right side to make it easier to disconnect.

And when you replace a sensor it sometimes helps to disconnect the battery to zero-out the ECM and allow the ECM to learn the new sensor.

Which speed sensor are you referring to? There are as many as 6. There is one at each wheel for the ABS system, there is a TSS(Turbine Speed Sensor-that helps the PCM decide which gear the transmission should be in and whether the transmission is performing correctly), and there is a VSS(Vehicle Speed Sensor-which also helps the PCM do transmission functions, operate the speedometer, and provides speed information for the cruise control).

It is in the back of the engine under the exhaust manifold. It can be accessed from the drivers side with a 10mm socket, universal elbow and a couple drive extensions. Hard to get at, but not to bad once you locate it.

At the top of the output shaft housing on the passenger's side of the transmission. If you reach down behind the back of the engine on the passenger's side, down to the transmission housing, you will probably put your hand right on it. It will be covered by a cardboard and foil protective cover.

ok here is the right answer for your question it is located on top of the tranny under the #2 cylinder between engine and fire wall and it is easier to see if you remove the air intake hose and have a good flashlight. hope this helps just changed mine last week.


It is called the "vehicle speed sensor". If i remember correctly it about $35 dollars at the parts store.

This sensor will make your car not shift out of first or hold out first a lot longer, and at times you may not have a speedometer. It is located on the tranny directly below the intake manifold. This is a hard one. I crawled on top of my car and laid the side of my face on the manifold. please do this when its cold. Arms on both sides till you find this thing sticking out at a 45 degree angle pointing towards the driver seat. Its only one bolt 10mm, I think. finding where that bolt goes back without being able to see it is the hard part. Good luck 20 minutes for me.

Answer - 1993It's not easy. The (VSS) sensor itself is only held in with one 10mm bolt, that isn't the problem. It's getting to the sensor. The sensor is located in the hardest spot imaginable to get to. On top of the transmission output shaft housing, sandwiched down behind the engine and the passenger's side area of the firewall.

You will probably have to jack up and remove the RF wheel, and it will probably take a combination of working down behind the engine from the top with a super long socket extension with a 10mm flex socket, and working inside the RF wheel well. the sensor is at the end of the speedo cable, buried under a cardboard and foil covering.

After you get the old sensor out, make sure you transfer the speedo gear. It is held on with a metal clip.

The only other problem here is that, once you fight half a day to replace this sensor, your problem may still not be fixed. I find that many times, the sensor is not the only problem. Deep inside the transmission there is a plastic gear that drives the VSS. Often the VSS is misdiagnosed because the real culprit is that the drive gear is stripped. If it is, the transmission will have to come apart to fix. You are doing the right thing by replacing the VSS though, because there is no way to determine if the drive gear is the problem until you try a VSS first. Click Component Location.

Car Computers and Sensors
Ford Taurus
Crankshaft Sensors

Where is the camshaft position sensor - CPS - located on a Mercury Sable - Ford Taurus?


Diagnostic Trouble Code (DTC) P0340 - Camshaft Position Sensor

Your cam position sensor or the wiring leading to it has gone bad. It will cause occasional rough running and hard starting until it is replaced. If you live in a county that does emissions testing, your car WILL FAIL unless it is fixed.

AnswerIf you have a 3.0 12 valve engine is is located at the rear of the engine block, under the throttle body area.

If you have a 3.0 DOHC 24 valve, it is located on the timing cover, held in with a 8mm bolt.

AnswerThe cam sensor is on the drivers side, on the intake manifold a few inches down from the intake air hose ,back of engine, it is in there sort of tight, I am still trying to figure the best way to take it out. AnswerWhat engine? On a Ford 3.8L Engine, the cam position sensor is on the right side of the engine, in the front, near the A/C compressor, it is above the crankshaft position sensor, and since they have the same connector, don't mix them up, the cam is above the crank, on the 4.6L engine, the cam sensor is on the left side, under the power steering fluid reservoir. AnswerIf it's the 3.0 OHV engine it's located on the driver side of the engine between the throttle-body and spark distributor back under a wire bundle. It's located where the mechanical distributor used to be. AnswerWhat engine? On a Ford 3.8L Engine, the cam position sensor is on the right side of the engine, in the front, near the A/C compressor, it is above the crankshaft position sensor, and since they have the same connector, don't mix them up, the cam is above the crank, on the 4.6L engine, the cam sensor is on the left side, under the power steering fluid reservoir.

The Cam position sensor on my 97 Ford Aerostar 3.0 replaced the distributor Is mounted on top at back of motor sits atop of the lower half of distributor/oil shaft mount .Check there. Found out it's called a camshaft synchronizer that it's mounted on.

AnswerIf you have a 3.0, 12 valve engine, it is buried under an engine wiring harness, at the rear of the engine, close to the throttle body, near the top of the transmission bellhousing, on top of the CAM synchronizer, held on with two 7/32 screws. If you have a 3.0 DOHC 24 valve, it is located in the timing cover, held on with one 8mm bolt. Answerwhich 3.0 do you have? The 3.0 12 valve, (VIN code U-8th digit), or the 3.0 DOHC 24 valve(VIN code S)? AnswerMy Fault I should clarify that answer, (I just found the thing myself) it's on the driver's side under the wire harness that runs under the intake (beside the spark plug wire holder). The thing bends a piece of metal that's suppose to revolve around the magnet of the sensor. AnswerIf you are talking about a 3.0 (12 valve), it is on the camshaft position synchronizer at the rear of the engine under the engine control wiring harness, below the thermostat housing area. If you are talking about a 3.0 (24 valve), it bolts to the front of the timing cover with an 8mm bolt. Replacing the Sensor1. Disconnect the negative battery cable...just like on every other installation 2. Detach the CMP sensor connector next. 3. Remove the CMP sensor retaining bolt and remove the CMP sensor

Now to install: 1. Clean the CMP sensor surface and ensure that the O-Ring is in place. 2. Position the CMP sensor into the engine and tighten the retaining bolt to 71-106 inch lbs. 3. Attach the CMP sensor connector 4.Connect the negative battery cable.

Answerthe sensor is a little black connector and box right next to the crank shaft if you are standing on the passenger side of the car look straight down to the bottom pulley you will see the plug with a wire on the left side AnswerIt is located on the right hand side of the engine (you standing at the front of the car) under the wiring harness going up into the engine to the left of the throttle cable. Real pain to get at and replace but can be done with no special tools. 7/32 in. wrench is the only way to get at it.

I am in the process of changing mine now. You have to remove part of the throttle assembly and unplug some things to be able to move the wiring harness enough to get to the bolts. It's not really to bad though I fear I might need to replace the entire assembly requiring me to remove the intake and entire throttle assembly. My 02 Taurus SE runs fine but squeaks from the assembly. Hopefully your Taurus only needs the sensor. S

AnswerThe cam sensor is on the drivers side, on the intake manifold a few inches down from the intake air hose ,back of engine, it is in there sort of tight, I am still trying to figure the best way to take it out.
Car Computers and Sensors
VW Jetta
Ford Expedition XLT
VW Sharan

What happens when a mass air flow sensor goes bad?

High Fuel Consumption

Halious-Other problems are, severe drop in power, inability to accelerate, stalling out, & your wallet gets a lot lighter(Cheapest one we ever replaced at my shop was $298 at cost.) Despite the important sounding name it's easy to replace. It lies somewhere between the air filter & the throttle body buy a new one and compare it to parts you see along the air intake system(A lot of German cars like VW & Audi put them in the air filter box bolted to the top section that you lift off to see the air filter. Chevy likes to put them right in front of the throttle body. Usually prettty easy to find & work on.). A few bolts, & a couple wires. At least save yourself some money on labor costs.

Note: Mass air flow sensors can be cleaned to restore performance in most cases without having to replace them. The hot wire variety can be cleaned with isopropyl (rubbing) alcohol, electrical contact cleaner, or aerosol cleaners specifically designed for Mass Airflow Sensors . NEVER use carburetor or throttle body cleaner as these are too harsh for the delicate platinum wires. There are many cleaning methods that can be found by an internet search. In rare cases, your car may have a Karman-Vortex type air sensor and these cannot be easily cleaned and are more often found on cars that are either turbocharged or supercharged. When your mass air flow sensor goes bad, it cannot react properly to changes in the air entering your engine, so it will provide either too little or too much gas for your airflow, causing issues such as hard starts, rough idle, sluggish throttle response, and pinging.

Car Computers and Sensors
Car Electronics and Lights
OBD Diagnostic Codes

What are the OBD-II pins?

Honda Man'sSince we don't know what make, model or year your car is, this is a difficult question. If it is in fact OBD II, the connector should be located under the driver's side dash.

In order to find your codes, you don't need to plug into the obd2 port. On the bottom right side of the diagnostic port, there should be two pins rather close together. My recommendation is to go to Auto Zone. Some of their stores actually have a key for checking GM obd1 systems. It looks like a key, and has two prongs on it that plug right in to where you need to check your codes. If your local store does not have one, then my advice is to look on the port and find the two bottom prongs that are closest together and jump them.

I have the exact same pinout on my 1995 Buick LeSabre. I have been researching this issue for some time now. The VECI label abve the radiator in my car states "OBD 1 Certified." However, I believe this is only stated because the pinouts of the connector are wrong. I have the VIN L engine, and all technical docs for that engine point to it being controlled by a PCM. PCMs do not report codes by flashing the SES light, only GM ECMs do. GM cars with an ECM and a 16-pin J1850 non-OBD-II connector on them, have a pin-out of 4,5,6,9,12,16. You short pins 5 and 6 to receive diagnostic trouble codes via the Service Engine Soon light. As you can see, those pins do not light up with our common connectors. Our connectors use pins 4,5,8,9,14,16. What I can tell you about this connector is as follows: 4=Chassis Ground, 5=Signal Ground, 8=Keyless RF Trigger (short to 5 to enter program mode), 16=Battery+. (Note 4,5=Ground 16=Battery+ are standard pins for the OBD-II standard. Yet another thing that points to an OBD-II serial uplink.) 1995 was a transition year for GM, in many different aspects including OBD-II. I believe what happened, what the pins were installed in one order believing that they conformed to standard, and then the standard changed before finalization. For more information on this, check out my regular posts to Automotive in the Buick LeSabre forum. This is my latest:

Buick Park Avenue
Car Computers and Sensors

Can you drive without air flow sensor hooked up?


Car Computers and Sensors
Nissan Xterra

Where is the throttle position sensor located on a 2002 Nissan Xterra?

the tps is in differant places on cars and trucks, but most are on side of throttle body at throttle plate.

Car Computers and Sensors
Toyota Celica

How do you rewire a 1986 Toyota Celica derby car to bypass the computer and other irrelevant units?

Computer? Yeah, who needs it. It's only the heart and soul of your entire car. You can ditch the computer if you remove the entire intake and put on a carburetor, remove all the emission control components (remember to plug all the holes or you'll lose engine vacuum and that's BAD) and fabricate and install a manual fuel pump. Then replace the entire ignition system with an old "points" system that you'll have to replace every 3000 miles. (oh yeah, you'll have to tune that carburetor every year too). Have fun!

Car Computers and Sensors
Dashboard Lights and Gauges
Acura RL
Dodge Dakota

How do you reset the maintenance required light on a 1992 Dakota 5.2L?

The maintenance light,You will need to take it to a Dodge dealer to reset it. Or get a DBR-2 code scanner.BIG $$$

Car Computers and Sensors

Where is the map sensor in 2000 Suzuki Baleno?

Hello Dear,

The MAP Sensor in a Baleno 2000 is attached with Throttle body and can be seen clearly. It reads Sensor Pressure and in most Balenos the make is of USA.

Car Computers and Sensors
Toyota Corolla

How do you remove oxygen sensor from 1990 Toyota Celica ST?

First off use a spray lubricant very liberally on the threaded area of the sensor. (I recommend PB Blaster. It is a miracle in a can!) Secondly, cut the lead wire close to the sensor so you can use a socket on it. (preferably a 6 point to reduce the risk of rounding off the soft brass hex. Use 1/2" drive for leverage). when installing the new one use a crescent wrench. Do not over-tighten.


Car Computers and Sensors
Jeep Grand Cherokee Laredo
Jeep Liberty

Where is 2002 Jeep Liberty Transmission Fluid Pressure Sensor?

Just in front of crossmember, passenger side and near the bottom.

Car Computers and Sensors

How do you reset the 'maintenance required' light after 60 thousand miles?

Without the year, make, and model, an exact answer can't be given here.

However, in very basic, you will either need the code specific to your car, or you can run it up to your dealership. They can reset it in just a few minutes for a fee. From time to time, you can find the code directly in your owner's manual.

Car Computers and Sensors
Dashboard Lights and Gauges
Acura RL
Toyota RAV4

How do you reset the 'maintenance required' light after servicing a 2004 Toyota Rav 4?

Ya didnt look at the Gogle postings on this long enuf.... I dont own a 2004 rav , but i was doing some research on pt cruiser and got scared to death about what i read I guess im gonna buy the RAV !! aNY WAY THERES A POST that says all you need do is put the trip meter in Odometer... And shut the car off .. hold the reset button down and and turn key back on again ... KEEP HOLDING THE BUTTON IN !after a bit the light stops blinking and its all reset.. Daughters 1998 RAv 2wd 4door has been an absolute Gem ! requireing only tires , and standard maintenance for 48k miles..

Car Computers and Sensors
Dodge Dakota
Ford F-150

How do you change the speed sensor?

It kind of depends on what type of car/truck you have. Most fwd vehicles have the speed sensor in the transaxle above one of the axles. To change it usually requires removing a bolt and pulling out the sensor. Rwd vehicles either have the sensor in the transmission, transfer case(4x4) or in the rear differential. The replacement procedure is similar.

Car Computers and Sensors
Chrysler LeBaron

Where is the voltage regulator on 1990 Le baron?

The engine computer is also the voltage regulator.

Car Computers and Sensors
Ford Windstar
Ford Windstar GL
Ford Windstar LX

Where is the onboard computer on a ford windstar?

computr locationit behind the inde cowling cover next to the gas pedal?

I'm not sure, but i think the windstar (99) has two seprate computers, one is on the fire wall, and one is in front of hte passenger seat, under the glove box

the pcm is under the wiper cover on the pass side i just replaced one.

It is on the right-hand side and is only accessible from the engine bay. You have to remove the plastic cover against the windshield and remove the metal windshield wiper assembly. It is not difficult.


1995: Left inner fender just in front of the firewall

Car Computers and Sensors
Crankcases and PCV Valves
Dodge Dakota
Crankshaft Sensors

Where is the crankshaft sensor on a 1991 Dodge Dakota?

the 3.9,5.2&5.9 all have a crank sensor. It is mounted to the bell housing over the flywheel at the rear of the engine. You can back trace the wiring from the distributor to find it.3.9 does not have one. If I remember the v8s dont have one also,

[Edit] '87 through '91 'LA' V8 and V6 use a hall-effect cam position sensor in the distributor and have no crank sensor, '92 and up 'Magnum' use a crank sensor which will be mounted at the upper rear of the engine to 'read' the flexplate or flywheel through a slot in the bellhousing.[Edit] The part is called a "pick up coil" it's a round piece with a wire going into it you can access under the distributor cap and does essentially the same task as crankshaft position sensors. Only on the 'LA' 170hp V8.

Car Computers and Sensors
Oxygen Sensors
Mercury Grand Marquis
Pontiac Grand Prix
Grand Am SE

Where is the oxygen sensor on a 1996 Mercury Grand Marquis 4.6L?

On a 1996 Grand Marquis there are 4 oxygen sensors. 2 (1 on each bank) are mounted before the front catalysts near the manifold-->cat-pipe flange. These are the HEGOS or Heated Exhaust Gas Oxygen Sensor. These are the primary o2s and are what help the PCM determine the correct A/F ratio. There are another 2 directly after the fisrt set (1 on each bank) of catalysts moutned on the exhaust piping between the two catalysts on each bank. The primary goal of these is to monitor the catalysts' effieceincy. In summary: 4 o2 sensors in all 2 are the upstream/HEGOS o2s 2 the downstream o2s 4 cat-convertors in all

Car Computers and Sensors
Oxygen Sensors
Plymouth Voyager
Pontiac Sunfire
Honda Accord EX

Where is the Oxygen Sensor on a '94 Plymouth Voyager and how do you change it?

Hey Mario==It will be close to the exhaust flange and on some cars it is in the exhaust manifold. GoodluckJoe

Car Computers and Sensors
Isuzu Rodeo

What does the ion sensor do on a 2001 Isuzu Rodeo?

The ion sensor on a 2001 rodeo is in a sense a camshaft,crankshaft,knock sensors and ignition module all in one sensor. It does this by reading the signal each spark plug sends to it with info like, compression, knocks, and uses those signals to determine when to send the signal back to the coil pack to spark. Its a lot of work for one sensors and relies on the spark plugs to work correctly.

Car Computers and Sensors
Chrysler Town and Country
Dodge Ram
Ford F-250

How do you replace the input speed sensor on a 1999 Chrysler Town and Country LImited minivan?

The Vehicle Speed sensor is located on the side of the transmission. You would be best to remove the battery tray and air intake plenum to see it. Trace the fuse block wire going to the back of the transmission. it will be located on the Left side (looking at the motor) after the ribs pointing back at you. It should have one mount screw and when you pull it out it will have a magnet on the end of the sensor.

To replace the VSS, disconnect the electrical connector remove retaining bolt and it should fall right out.

Simple once you see it. that's half the battle.

Car Computers and Sensors
Nissan Altima

Where is the computer located in a 1987 Nissan Pintara Wagon so you can run a diagnostic test?

The computer is behind the left hand passengers side kick pannel. Remove the pugs, undo the screws and the pannel will pull away. Hopefully this helps! :D

Car Computers and Sensors
Chevy 350

What computer chip do you need for 350 engine?

it all depends on what "YOU" want horspower,speed,gas need to take a look at HYPERTECH they are a good company and have alot of diff kind of chips available for a 350 and other engines and apps


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