02-19-12 10:06 PM - Post#2192747 In response to LaMort
the 1228747 is not key because that is the most common ECU to find out there. Not only just our trucks but just about everything GM sold in that time. They started the 1228747 in trucks in 87 with the previous body style. My old friends dad had a suburban with a 350 tbi. I remember t/sing a high idle with him years ago and remember checking the knock sensor so I know that it was available from the start.
The other thing to consider is that the opinion given to you by the dealer is that the truck over heated because the ecu did not see a knock sensor and retarded timing. Well I have done some programming before on my old 88 and I know there are of course spark tables and an accommodation for the knock sensor in the code, even on the 1228747 with external ESC module. I believe the ESC module is a (forgetting the word) but like an amp that listens to the knock sensor like a microphone and then produces a digital signal indicating knock which is passed to the ECU as a knock count. There is a test sequence to verify the ESC circuit is functional by which the ECU induces a condition conducive to knock and if is sees none then assumes fault.
so what we are saying is that your ECU sees fault and is retarding the timing in caution. So if there was a none ESC module I would fully expect this code to not be in the programming so that it is a none issue. So either some one went to great lengths to cut this out and hide it or some one changed the ECU with the wrong prom (programming)
Other considerations is the base timing as listed under the hood. Factory is zero degrees at idle with timing wire disconnected. I would still expect to see this even w/ out the ESC circuit as the programming would adjust for this. Either way this is the first I have ever heard of this and the best thing I could come up with to support your theory is Mexico. This truck came from another country that did not require is and some penny pincher did his job a little to well?
Also when you key on, engine off, does your SES light come on? I would try pulling codes because this condition should throw a code. Easy to check with a paper click, short Pin A and B I believe, please confirm in FAQ.