service engine soon???

Hi all im new to this forum, i have an 89 caprice classic and gas prices are LAME. So anyways, I havent been using my "overdrive" gear because whenever I do the "service engine soon" light comes on. Any one know why this would be? Also, when am i suppose to use overdrive, over 50?
Thanks in advance

How do I read my computer codes?

Tools needed:
Your car keys
A paper clip or a three(3) inch long piece of safety wire.

First thing you need to do is find your Assembly Line Diagnostic Link or ALDL. It s small black plastic piece about two (2) inches wide by one half(0.5) inch tall. It has twelve (12) female connector inside. The ALDL can be found under the driver's side of the dash, usually attached with two (2) screws to the bottom side of the dash.

The ALDL :

Now that you've found the ALDL, bend the paper clip or the piece of wire into a U shape. With the ignition in the OFF position. Insert one end into the A slot and one into the B slot. Now turn the the ignition to the ON position. DO NOT start the car. As the ECM begins it's self-test if will begin to flash the SES light to provide the codes. The flashes will appear like this : *flash* short pause *flash* *flash* long pause then repeat. Each code will be displayed three(3) times. Code 12 will be repeated to indicate the end of the set codes. If you all you get is Code 12 then you have no codes set in your ECM.

An example of a sequence for a common code :
*flash* short pause *flash* *flash* long pause = Code 12, Testing the ECM
*flash* short pause *flash* *flash* long pause = Code 12, Testing the ECM
*flash* short pause *flash* *flash* long pause = Code 12, Testing the ECM
*flash* *flash* *flash* short pause *flash* *flash* long pause = Code 32, EGR
*flash* *flash* *flash* short pause *flash* *flash* long pause = Code 32, EGR
*flash* *flash* *flash* short pause *flash* *flash* long pause = Code 32, EGR
*flash* short pause *flash* *flash* long pause = Code 12, Testing the ECM
*flash* short pause *flash* *flash* long pause = Code 12, Testing the ECM
*flash* short pause *flash* *flash* long pause = Code 12, Testing the ECM


Clearing the codes is really quite easy. Unhook your battery for about 2-3 minutes and then hook it back up.

These codes cover the OBD-I computers only.....
All currently listed codes are from the 1989 B-car Service Manual. Why? Because that's what I have. If you have others that aren't listed or need to be added, just let me know.


CODE AND CIRCUIT POSSIBLE CAUSE

CODE 12 = System check
Indicates that the ECM is functioning.

CODE 12 = No Engine Speed Reference - VIN 'Y' CARB
Indicates an open or ground in the distributor reference circuit.

CODE 13 = OPEN Oxygen Sensor (O2)
Indicates that the oxygen sensor circuit circuit or sensor was open for one minute while off idle.

CODE 14 = Coolant Sensor (CTS)
Sets if the sensor or signal line are grounded for 3 seconds. HIGH Temperature indication.

CODE 15 = Coolant Sensor (CTS)
Sets if the sensor wires or connections are open for 3 seconds. LOW Temperature indication.

CODE 21 = Throttle Position Sensor (TPS)
TPS voltage of more than 2.5 volts for 3 seconds at an engine speed less than 1200 rpm. HIGH Voltage Signal.

CODE 22 = Throttle Position Sensor (TPS)
A shorted to ground or open signal circuit will set code in 3 seconds. LOW Voltage Signal.

CODE 23 = Manifold Air Temperature Sensor (MAT)
Sets if the sensor wires or connections are open for 3 seconds or Intake Air Temperature (IAT) LOW Temperature indication.

CODE 24 = Vehicle Speed Sensor (VSS)
No vehicle speed present during road/load deceleration. NO Vehicle Speed Indication.

CODE 25 = Manifold Air Temperature Sensor (MAT)
Sets if the sensor or signal line are grounded for 3 seconds. Or Intake Air Temperature (IAT)
HIGH Temperature indication.

CODE 32 = Exhaust Gas Recirculation (EGR)
OR Vacuum switch shorted to ground on start up. Switch not closed after the ECM has commanded EGR for a specified period of time OR EGR solenoid circuit open for a specified period of time.

CODE 33 = Manifold Absolute Pressure (MAP)
MAP sensor output too high for 5 seconds or an open circuit. LOW Vacuum.

CODE 34 = Manifold Absolute Pressure (MAP)
Low or no output from sensor with engine running. HIGH Vacuum.
CODE 35 = Idle Air Control (IAC)
IAC error.

CODE 42 = Electronic Spark Timing (EST)
ECM has seen an open or grounded EST or Bypass circuit.

CODE 43 = Electronic Spark Control (ESC)
Signal to the ECM has remained low for too long or the system has failed a functional check.

CODE 44 = LEAN Exhaust Indication
If voltage to oxygen sensor remains BELOW .2v for more than 20 seconds code is set.

CODE 45 = RICH Exhaust Indication
If voltage to oxygen sensor remains ABOVE .7v for more than 1 minute code is set.

CODE 51 = PROM - Faulty MEM-CAL or ECM.

CODE 52 = Faulty or missing CAL-PACK.

CODE 53 = System overvoltage
Indication of a faulty alternator or regulator. Camaro/Firebird uses a Code 53 for Vehicle Anti-Theft System (VATS).

CODE 54 = Low Voltage To Fuel Pump
Sets when the fuel pump voltage is less than 2 volts when reference pulses are being received.

CODE 55 = Faulty ECM

My guess = 32 EGR valve. Get your codes and report back.

How do I read my computer codes?


Somebody outta' give you a medal or something...what a great, helpful post!

I'm having intermittant "service engine soon" lights myself with my son's and will do just as you discribe when we get back from vacation. Started after the local Chevy garage replace the valve cover gaskets for a leak. I hope the leak was fixed - gotta' clean up the drips on the driveway to check for more now.

btw - my tire guy has our new rims and is mounting the Firehawks. We'll get them on late next week. I'll post some pics soon after.

hmm ok thanks? i dont really know much about car stuff so this is all a little confusing to me. But thanks for the post

I have posted that same post many times here. I'm surprised we can't get a moderator to pin it. I have it in a file in the files section of my yahoogroup if you need it again.

I have posted that same post many times here. I'm surprised we can't get a moderator to pin it. I have it in a file in the files section of my yahoogroup if you need it again.

thanks for posting all that, im just still a little confused. What exactly does it mean when it says "service eng soon" ? And should i be worried

thanks for posting all that, im just still a little confused. What exactly does it mean when it says "service eng soon" ? And should i be worried

Your car has what's called an ECM, or Electronic Control Module. This is a computer that controls emissions and maximizes economy, and power depending upon any driving condition experienced. This system relies upon a network of sensors located in different parts of the engine and transmission. If the engine isn't running quite right, or any sensor is reporting an invalid value for the situation, the computer will set a "trouble code" for diagnosing the issue. This in turn lights up a light on the dash either called "Check Engine" or "Service Eng Soon". It's not necessarily the engine, it could be a bad sensor. Fuel problems, mixture problems, temperature problems, engine cylinder firing problems, all will cause this light to come on. It could even be something as simple as a dirty air filter!

Your car has what's called an ECM, or Electronic Control Module. This is a computer that controls emissions and maximizes economy, and power depending upon any driving condition experienced. This system relies upon a network of sensors located in different parts of the engine and transmission. If the engine isn't running quite right, or any sensor is reporting an invalid value for the situation, the computer will set a "trouble code" for diagnosing the issue. This in turn lights up a light on the dash either called "Check Engine" or "Service Eng Soon". It's not necessarily the engine, it could be a bad sensor. Fuel problems, mixture problems, temperature problems, engine cylinder firing problems, all will cause this light to come on. It could even be something as simple as a dirty air filter!

ohhh ok that makes more sence! thanks so much
the light isnt always on, only sometimes when i put it into overdrive. Next time it comes on i'll check it out. Thanks again guys!

Like robin's, the light on our '83 is on intermittantly. The day after the valve cover gaskets were replaced, it came on and stayed on at highway speeds then went off when the car slowed down. Prior to that repair the light was not coming on. Since then the car has only been driven around town a little bit and light has come on just briefly a few times.

We are having some dieseling (sometimes pronounced) and I've not yet been able to adjust, what to me, seems to be a fast idle. The dieseling was there before the repair.

I'll check codes when I have time late next week (I hope!) but in the mean time would you have any thought about a source from what little I've told you?

Also wondering about the cat. An '83 with 92,000 miles - is it likely in need of replacement yet, or is age and mileage not a good indicator of that?

Also wondering if the carb may need rebuilt. The Chevy garage recommended the carb be rebuilt (@ $400 - wow, is it that much?) after my inquiry about the fast idle.

Given your description, my wild guess is that you are having a problem with the EGR. The '89 TBI systems use the MAP sensor change to determine when the EGR was active (open). If the ECM commands the EGR solenoid to operate the EGR valve, and the ECM does not detect a corresponding increase in MAP (drop in vacuum) the "CHECK ENGINE" lamp will light.

It is also possible that the ECM is not detecting a 4th gear signal from the transmission switch, and is trying to operate the torque converter clutch but does not detect the proper drop in engine RPM.

The easiest thing to do is acquire an GM OBD Diagnostic Code Scanner (also know as a paper clip) and insert it into the ALDL connector in the passenger compartment. The whole process takes about five minutes if you're really slow.

CD Smalley covered it quite well, but here's a different approach in case you need more visual aids:

First, you'll need to acquire a GM OBD I ECM Diagnostic Trouble Code Retrieval Tool (commonly known as a paper clip). Form this wire into a ‘U’ shape.

With the engine and ignition turned off, locate the ALDL connector under the dash, just to the right of the steering wheel in the driver's foot well area on some models, and on the left on others, depending on the make and year. There should be a small rectangular cover over the access hole in the lower dash trim, or at least was when the car was delivered.

http://72.19.213.157/files/ALDLPlug.jpg

Insert a tool as described above (paper clip) into the 'A' and 'B' terminals on the ALDL connector:

http://72.19.213.157/files/ALDL.gif

WITHOUT STARTING the engine, turn the ignition to the "RUN" position. Watch the Malfunction Indicator Lamp (MIL) - it will begin to flash. This is also commonly called the "Service Engine Soon" or "SES" lamp. The first code will flash three times, and will usually be a code '12'. This is encoded by one flash of the lamp, a brief pause, then two successive flashes of the lamp. Each code will repeat three times, so you should see a "Code 12" flash three times. Any other error codes will follow in numerical order, and each code should flash three times. After all codes have been displayed three times, the "Code 12" will again flash three times, then all other codes will follow as described earlier. This cycle will continue until the jumper is removed or the ignition is turned off.

After you have made a note of all error codes, turn off the ignition and remove the jumper immediately. If you forget to remove the jumper and attempt to start the engine with it in place, you could damage the ECM. For this reason you should remove it immediately.

Once you have a note of all error codes, check this file for the decoding:

GM Error Codes.pdf (http://72.19.213.157/files/GMError.pdf).

You'll need Adobe Acrobat Reader (http://www.adobe.com/products/acrobat/alternate.html) to open/print the file.

Keep in mind the picture of the dash he showed above is for a Camaro. On a boxy Caprice, the ALDL is located below the dash in about the area of your left knee. It should have a plastic plug on it that says "DIAGNOSTIC". Simply pull this off and set it aside.

As for the '83 B-Body, the procedure is the same, but the error codes will be different. The early CCC system (of which your's is one) had a more limited diagnostic capability. Still, retrieving the stored codes is a good aid to diagnosis.

Again, your symptoms indicate a dead or poorly functioning EGR, and possible combustion chamber deposits contributing to the detonation and run-on (dieseling).

To reduce the potential for run-on, make sure the curb idle is properly adjusted, and the idle solenoid is functioning and adjusted correctly. Youll need to perform a few checks and possibly some adjustments to the carburetor. It's not difficult, and the carburetor is not a highly complicated assembly:

http://72.19.213.157/files/E4MEexplode.jpg


Part of this check and adjustment is going to require that the choke is operating, clean, moving freely, and adjusted properly. With the engine fully warmed, ascertain the choke is fully opened and the throttle screw on the right side (passenger side) of the carb is not touching the choke high idle cam.

Locate and read the VECI label under the hood. It should look a little like this for an '83:

http://72.19.213.157/files/DTWLabel.jpg

PROCEDURE:
Connect a diagnostic tachometer to the HEI cap terminals; Disconnect the high idle solenoid (if equipped); Set the parking brake and chock the wheels; Have an assistant place the transmission in DRIVE and hold the service brake for added safety. Make sure the air conditioner and all other accessories are off. Set the curb idle adjustment to the RPM specified on the VECI label under the hood (usually 500-550 RPM in DRIVE); Have your assistant place the transmission back in PARK, and reconnect the idle soleniod (if equipped). If the solenoid extends, breiefly raise the throttle to allow the solenoid to stop the throttle in the proper position; Have the transmission again placed in DRIVE and adjust the idle solenoid to the specified RPM listed on the VECI label; Have the transmission set in PARK and shut off the engine; Remove the wheel chocks and your diagnostic equipment.

If you changed the adjustments significantly, especially the curb idle setting, you should also readjust the TPS to the correct voltage.

As part of the procedure, you may want to try to clean the combustion chambers of accumulated carbon and coke. While many suggest using products such as SeaFoam or other mixtures for this, I've had better success using either plain water or windshield washer solvent. Given that the most effective cleaning agents in the SeaFoam are the 40% water and 10% isopropyl alcohol in the mixture, and that SeaFoam is usually $5-6 in one pint cans, a gallon of a water/methanol mix (windshield washer solvent) at 99¢ is more effective and a lot cheaper.

Make sure you administer whatever cleaner you use slowly enough so that the liquid cannot enter the chambers in sufficient volume to create a hydrolocking situation. You'll quickly go engine shopping if that occurs.

If you are wary of this, you can also use GM Top Engine Cleaner and follow the directions. It also works quite well to remove deposits.

Keep in mind the picture of the dash he showed above is for a Camaro. On a boxy Caprice, the ALDL is located below the dash in about the area of your left knee. It should have a plastic plug on it that says "DIAGNOSTIC". Simply pull this off and set it aside.

Actually, that photo is for a Firebird. Most Camaros (not ALL) had them on the left side of the steering column, beneath the light switch.

Actually, that photo is for a Firebird. Most Camaros (not ALL) had them on the left side of the steering column, beneath the light switch.

Oh, well I stand corrected then! :) At least I got it part right (it's an F-body) :P

Good eye! And no, you're not corrected. It seems some of the years of F-Body Camaros prior to OBD II had the ALDL on the right side
of the column, too. So, you are correct, too.

For ddax, FWIW, if you perform the idle adjustments and discover the need to adjust the TPS as a result, this might come in handy:

Rochester E4ME Adjustments.pdf (http://72.19.213.157/files/E4ME.pdf)

thank you so much! the visuals helped alot. =) I will have to try this when i see that light turn on again. I really appreciate all your help

Thanks a lot guys - what a great board! I'm off on vacation but will work on this next week.

Robin, hope you don't mind my highjacking your thread for my use as well

You don't need to wait for the light to come on again. If the code is stored, and I am sure it is, thei procedure will tells us that code now.

CD is correct (again). The error codes are stored for 50 subsequent engine start/run cycles, so as long as you don't exhaust the number of starts and push the stored data out the end of the register, they should still be there. Get the error code(s), and you'll have all weekend to diagnose and solve the problem.

Robin, hope you don't mind my highjacking your thread for my use as well

That will cost you DOUBLE your normal subscription fee...