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Discussion Starter · #1 · (Edited by Moderator)
New to the forums, struggling with a solution for the wife's car (owned since new). A few months back it would randomly go to "reduced power", but recovered with a key cycle and didn't set any codes (this got the throttle body replaced). Finally it "stuck" in reduced power and set a code. The initial codes were P0091 Fuel Pressure Regulator 1 Control Circuit Low and P0087 Fuel Rail/System Pressure - Too Low Bank 1. Research suggested the in tank pump was the likely culprit, so I changed that, followed by the fuel pump control module. Then the high pressure fuel pump, the ECU/PCM and finally the fuel rail pressure sensor. Each part was replaced and the car faulted before the next part was installed. Each part was replaced in order of "the most likely" cause based on the trouble codes.

Over time the fault code has morphed from simply P0091 (low) to include included P0627 (open) and today the ONLY code that remains is the P0627.

I have checked the wiring to and from the various fuel components I have replaced and find nothing loose and don't see any bad connectors or obviously broken wires. I am out of ideas and wonder if anyone else has had a similar problem and managed to solve it. Perhaps a mystery ground strap???

Below is a graph of the data I have most recently collected. This was prior to changing the pressure sensor (yesterdays task). You can see that things look good for a while - actually on a cold start it takes 10-20 minutes to get the "reduced power". Everything seems in line then the HP pump dials to "off" (no idea how that is done) and the fuel tank pump goes to max. With only ~100 psi to the direct injectors you are in "reduced power".

You can re-set the the reduced power by disconnecting the battery, but if hot it comes back nearly immediately. If cold (overnight) it seems to be good on crank and the fault re-occurs in 10-20 minutes.

The idea that it was heat related is what drove me to reluctantly change the ECU (I have experienced similar issues with headlights on an older car that had bad grounding straps - where should I look?). There are no fuel pump relays that I find, so assume that function is built into ECU.

Any help appreciated.

H

Acadia Fault.jpg
 

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If you don't have a service manual, you'll find links to several in another forum section. Diagrams in the 2010 or 2014 manuals may help you locate grounds for the Acadia's fuel pump circuit. Little with the fuel pump circuits has changed through run of the Lambda platform since the switch to GDI engines in 2009.

Try establishing an alternative ground to the fuel pump circuit. That should help to determine if there's either a ground, or power supply problem. Good luck!
 
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