GM E67 ECM low reference voltage
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Staging Lane
Joined: Jul 2015
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GM E67 ECM low reference voltage reference voltage to my CKP sensor was about 1 volt causing engine to shut down and display a DTC. I measured voltage out on ECM terminal to be about 1 volt as well, so for some reason the ECM has failed. I moved the 5v reverence to an unused 5V reference terminal and got good 5v at CKP terminal and replaced sensor in case that was issue. Question is, the E67 divides the reverence 5v into banks of about 4 or 5 seperate sensor terminals..... does the ECM care where the 5v reference comes from? In my case, I am wiring the CKP 5v reference to unused EGR reference, which is on other bank and working fine. Also checked 5v ref wire between CKP and ECM connector, was 2 Ohms so not the issue.
2nd question,... can a 5V reference failure be fixed inside ECM?
2nd question,... can a 5V reference failure be fixed inside ECM?
Since nobody replied I'll throw in my 2 cents.
Since the CKP is one of the few sensors that will kill the engine if the 5v goes bye bye I'd be extra sure. I don't think there's any strategy in the PCM that would ever drop EGR 5v but that would just bother me knowing that's the source. Could overheat mode or something kill that? Probably not but I just don't know. This reminds me of people who want to "hotwire" the alternator exciter with 5v in swaps, I think sometimes they use an external standalone 5v power supply, you may want to look into that. If it were me I'd just get a new PCM and make it right. Future troubleshooting things is so much easier when things are "by the book".
Since the CKP is one of the few sensors that will kill the engine if the 5v goes bye bye I'd be extra sure. I don't think there's any strategy in the PCM that would ever drop EGR 5v but that would just bother me knowing that's the source. Could overheat mode or something kill that? Probably not but I just don't know. This reminds me of people who want to "hotwire" the alternator exciter with 5v in swaps, I think sometimes they use an external standalone 5v power supply, you may want to look into that. If it were me I'd just get a new PCM and make it right. Future troubleshooting things is so much easier when things are "by the book".
Last edited by mk3cn4; Feb 8, 2023 at 09:15 AM.
