2005 XC70 Fuel pressure/P0089 code

[stickman776]

Here is the background, it is a 2005 XC70 with 191,xxx miles.


Seven months ago I replaced the fuel pressure sensor due to loss of power and misfire issues when the car was acting like it was out of fuel, the car did not throw a code at that time. All was good up until about a month ago, the same symptoms came back, but this time a P0089 code.


So I replaced the sensor again, and the fuel filter, it did not help. When I checked the fuel pressure it was 41 PSI, so I replaced it with a new Bosch fuel pump, and it still would act like it was running out of fuel.


The PEM module is still in the original location and looked like crap, and it had corroded contacts, I replaced it with a used unit making sure it has good contact, and still it has issues.


Now when I start it up checking fuel pressure with both a scan tool and gauge it starts out at 58 PSI and slowly drops to 46 PSI, I understand that this is normal, but I eventually get a P0089 code again.


I have checked the plugs and coil packs, they are all good.


I left the pressure gauge on the fuel rail overnight and it is still holding 24 PSI, so I am ruling out any leaky injectors or a bad check valve in the fuel pump.

This morning I took the car out again, when I started it the fuel pressure was 58 PSI and then dropped to 46 PSI. The P0089 code came back, I cleared it and drove for almost an hour varying from highway to town driving and the fuel pressure stayed between 46-53 PSI depending upon load. If I stopped the car and shut off the engine and restarted the engine I would get the 58 PSI and then drop to the 46 PSI, but the CEL would come on and give the P0089 code. After an hour of all of this I was letting it idle and the fuel pressure dropped to 20 PSI and would not come up again until I shut off and restart the engine.
I am now leaning to a bad used PEM module, does anyone know how to test the module?

I am at a loss as to what to look at next.

[stickman776]

Well I took it out again after checking all of the connections, as per usual it would start out at 58 PSI, this time the fuel pressure drop down to 9-10 PSI and would not recover until I would shut it off and start it back up.

[jimmy57]

Check the ground coming into PEM with engine running. You could have a bad ground, the PEM is the ground path for fuel pump also. Voltage on the ground wire should be no more than 0.3V .

[stickman776]

Well I gave up and had a local shop that specializes in Volvo's do diagnostics on it, the conclusion was a bad new fuel pump assembly. They were able to catch it when the fuel pressure dropped to see if it was getting a good signal as well as voltage to the pump. They also tested all of the grounds for me as well. They charged me only $58.00 to do all of the testing.

I contacted the company I purchased the fuel pump from and had to buy a new one, they will refund me when the get the bad fuel pump back.

The car starts and runs as it should, fuel pressure on the scan tool and at the rail is 46.5 - 47 PSI, and seems to adjust to load much better, going up to 52-53 and as high as 56 PSI under load.

Thanks for the suggestions, and I hope this helps someone else with the same issue.