Hey, I've got a 88' sports coupe camaro, with a 305 and the "check engine soon" light sometimes comes on only during my drive in the freeway. I was wondering if anyone knew how to check it manually.
Thanx,
Thip22

 

jump the A and B terminal of the ALDL and count how many times the light flashes one pause two is 12, it'll do that 3 times then give you any stored codes and flash 12 again at the end when it's finished

 

Bets are its the EGR... code 32.

 

just incase you don't know how to jump the ALDL, i'll be more explanatory because the first time somebody told me "short A and B on ALDL" i was like duh wtf? lol slade

if you look by your fusebox, a little to your right probably under your right knee you'll find this little box with i think 8-10 sockets in it. the two in the topright corner... those are the ones you need... stick a paperclip end in each to join the two together.

then move your key forward (DONT START YOUR ENGINE) just so you have power. look at your service engine light. first it should flash 3 times and give you a code 12 just to tell you it's going to check. after the code 12 it will give you all other codes 3 times.

the way to read the codes is like this...

let's say the SES light flashes like this...

FLASH pause FLASH FLASH

that is a code 12. then it will repeat that 3 times.

FLASH FLASH FLASH pause FLASH FLASH is a code 32.

u get the idea. i had the same problem as you a few days ago and mine turned out to be a code 32. which is a vacuum leak..

 

Just to confuse the issue further:

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.)