Hi-

I have a code 43 and I believe that my timing is so retarded that the self test is failing. I have it set to 6 degrees BTDC- stock TPI motors usually call for 6 degrees. I have a different engine though. I've seen in various posts from various forums that many folks have experienced success with 10-12 degrees of advance for a carbed set up for the GMPP 12499529 engine.

Can anyone describe how the self test actually works? If memory serves me, I think the ECM advances the timing until it gets a knock- then, it sets it back- all as part of the process to determine if the ESC circuit is working. If my timing is too far retarded, I feel it is likely that I'll never get detonation on a 8.5 squeeze motor within the 20 degree parameters for ECM advance.

Thoughts?

I have a 7730 TPI system on a GMPP 12499529 engine with 1.6 rollers, SLP runners, and 24lb injectors.

 

I found a post where RBob explained the self test at a high level.

FWIW... my knock sensor checks out in terms of GM service procedure ohms, #496 checks out for voltage.

If I clear the codes... the light stays off for anywhere from 10 (warm) seconds to 2 minutes (cold). I believe that is related to the self test.

I'm going to set the base timing to between 10-12 degrees and see what happens. I've heard that my engine seems to like a lot of advance to compensate for low compression and a (relatively) big cam.

 

Timing set to 12 BTDC, new knock sensor, new ECM... no code 43!!!!

 

Cool. Don't mean to hijack. But, for a new ECM, did you have to replace the whole ECU? Is yours on the MEMCAL in the ECU?
Thanks, hope all is working good.

 

Memcal was okay... PCM for less programmed the MEMCAL.

The ECM itself was bought used off ebay. I had no guarantee on the ECM. Really, I figured it would go out sometime and I'd replace it with one that had a waranty. I bought that ECM a year ago.