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Does anyone know or has seen why the desired high pressure would go to 0? It even says 0 on the key on engine off. When it goes to 0 it has very negative fuel trims. High pressure does not bleed off with key off. If the rail pressure sensor was bad I could see desired at x amount and actual at 0
Yes, my data looks nearly identical to yours. The high pressure pump and fuel rail pressure sensor were already replaced before I got to the vehicle. The pump is aftermarket not OE so I've been suspicious of it the whole time but the desired dropping to 0 is certainly odd..
I'm also getting a P0172 rich code but only after P0191 sets and it goes into reduced power mode. My fuel trims go to -27 immediately after P0191 sets. This is somewhat intermittent too, only happens while idling in gear after coming to a stop. I have not found a lot of info for this code and the set criteria isn't all that clear but I believe we have ruled out anything electrical/PCM related as a root cause. I appreciate your input!
That’s when mine would act up. Seemed like when sitting at a red light. I put a pcm in it because the low side pressure matched desired and was confused why it wanted 0 psi for the high side. But I used an oem high pressure pump. I think it’s the solenoid on the pump that was the issue. Cars been running good since for the customer for 3 months.
Ya, the desired and actual pressure pids did not make a lot sense with what was happening. I agree with you that the solenoid was causing the issue, I have some scope captures of the solenoid when it would act up. It looked like the PCM was trying to command it on but the solenoid was not moving. Not sure why it wouldn't code for the pump/solenoid. The shop working on the vehicle installed a OEM high pressure pump and reported back to me that it was fixed. Again, thank you for your help on this one!
Only reason I knew was because it took me a few days to figure out. Called a pcm that didn’t fix it. Then the pump did. Ate the pcm it was only 200 from gm.
I’m fighting the exact symptoms on a 12 equinox, only I also noticed the low side pressure would drop to to 16 ish sometimes at low speeds, high pressure desired reads 0, when code p0191 pops up limp mode shows up on dash. I installed an aftermarket hp pump a month ago cause it was leaking gas into motor. What do you think about it? I was thinking it was because of low primary pressure but this thread kind of indicates hp pump problems
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