Engine light on @ idle
 

Hi everyone,
My son has a 1993 S-10. The engine light comes on whenever he puts it in park and lets it idle. If you put it back in gear, the light goes off. He took it to Advance Auto to have the codes checked, but it was to old for their equipment. Anybody seen this before? Thanks, Tom

Re: Engine light on @ idle
 

"too old for their equipment"?! they don't have a $2 code key?!
jumper pins A and B, turn key on, and watch the light flash the codes.
flash...flash-flash (3 times = code 12, OK now it's time for the problem codes)...longer pause, then (example) flash-flash-flash-flash...flash-flash-flash-flash-flash 3 times (example) means code 45 (rich exhaust IIRC)
it will cycle through the codes in numerical sequence with a long pause in between and then go back to a 12 signifying the cycle is complete.

Re: Engine light on @ idle
 

Here are some web sites with the basics on retrieving codes from the ECM without a scan tool or code reader.

Poor drawing of ALDL/DLC but ok instruction + codes
http://www.cfm-tech.com/gm_tbi_trouble_codes.htm

OBD1 terminal identification
http://robertpowersmotorsports.frees.../ALDL_plug.jpg

OBD1 illustration and instructions
http://www.troublecodes.net/GM/