I recently was having a problem with the Service Engine light coming on. I took it in and had the following replaced

Water Pump
Thermostat
Heater Control Value
All Cooling system hoses (they were original 1989)
Flushed the cooling system

My mechanic could not get the service engine light to come on again and when he tried to pull the code, the computer had none.

I took my car on vacation (about 270 miles one way) and the light didn't come on until I stopped (about 220 miles in) and then drove again. The light came on for about 20 miles and then went off.

On my way back, the light came on about 5 miles down the road and about 20 miles later it went off again and stayed off until I arrived home -- 245 miles later.

Any ideas as to what this is doing? Since there was no code before, I am assuming that there is not one now. If it comes on again while I'm driving I'll take it to AutoZone as they will pull the code for free.

Any thoughts?

Vehicle info:
1989 Camaro RS Convertible
V8 305 TBI
Auto Trans
55,000 original miles

 

Yes, check the main page for "how to" info, pull the code yourself through the ALDL with paperclip.

Tell us what it says, and we can go from there

 

#1. I'm guessing that the mechanic got at least one error code - a '12';

#2. Never assume anything until you've checked it yourself. Scan for codes.

If you need a refresher, here's a quick rundown:


First, you'll need to acquire a GM OBD I ECM Diagnostic Trouble Code Retrieval Tool (commonly known as a paper clip to TGO members).

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. There should be a small rectangular cover over the access hole in the lower dash trim.



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



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.

(You'll need Adobe Acrobat Reader to view/print the file.)

 

did your mechanic disconnect the battery before servicing your car/ if so then he erased all the codes. As soon as light comes on, check it. Even it light goes off. the code will be saved in the computers memory

 

spring loaded pins inside the aldl port sometimes bend so that a scantool won't make proper electrical contact when plugged in.

 

If your check engine light is on and you don't get any code...even the 12 default...I would drop the panel down on the passenger side and make sure all your connections are tight on your ECM. I had to replace the computer in my 85 SC and when it went it just lit the engine light, but you couldn't get any data, even with a scan tool.