I've done a few searches, but haven't found a good answer to my exact problem. I'm working on an '87 IROC. The engine runs great, but the temp gauge is acting funky so I wanted to hook up the Snap-On scanner so I could see what the temp sensor for the ECM was reading. The scanner says "No communication", however, I can jump the terminals to make codes flash with the SES light. Any ideas?

 

ign on engine off does the SES-CE light blink once then solid on? If yes that tells you ECU should be OK as well as the chip.

 

Yeah, the check engine light does the blink once then solid on thing. I think I may have figured out the problem over the weekend. I'll update this post when I verify.

 

Ok, what if i turn the key into the "on" position and then i just get a solid engine light? I do not have the single blink and then solid on. I just have the solid on. Also, i can not connect with any software programs like Datamaster or Freescan, or EFI live. I even had a Max 232 aldl cable built professionally and have also tried the simple two transistor circuit with no success. Do you think I may have a bad ecm or prom? If so, which one?

 

ign on - solid light means you are not running off prom. rapid blink is a defective prom.

 

ok, just checked again, i do get a super fast single blink then a solid light. Still no connection through aldl port. Any ideas? I even tried orange wire on the ecm A8.

 

That is normal. Runnin off the prom. Can you cause the CE/SES light to come on by (?) disconnecting a sensor as a test?