P0090 and P0087 Code after I took it to a mechanic

[bengal1001]

I have a 2012 QX56 that I recently took to a shop for P0300 and misfires. They changed the camshaft variable timing solenoid and the problem was fixed. It came out of the mechanic with the above two codes. The following are the symptoms I've noticed:

1) It will not accelerate hard when I fully depress the gas. The RPM will increase but with no change to acceleration. It doesn't stutter, misfire, or run poorly at all and as long as I'm not trying to accelerate quickly, it runs like it has no issues

2) First start of the day is a little rough. Sometimes I'll have to press the start button more than once to get it started. Doesn't seem to be difficult to start after it is warmed up.

I pulled the airbox and looked everywhere around the timing solenoid and the cam shaft position sensors and have not seen anything obvious that is unplugged. Is there a pressure sensor somewhere or something else easy that can be unplugged?

 

[primov8]

Those DTCs are all fuel related. There’s a series of things to check to diagnose whether those DTCs are being caused by either the low pressure fuel pump (in-tank), high pressure fuel pump or even both. I’m surprised the shop gave your truck back to you knowing those DTCs exist.

Besides an in-line fuel pressure gauge, you’d need a full range scan tool to diagnose the fuel pumps, particularly the high pressure fuel pump. The HPFP is diagnosed by reading the mV outputs at idle and while revving the motor.