Fuel pressure issues. CEL P0090, P0088, P0101

johnboy77 · Post by **johnboy77** » 14 Dec 2018, 20:09

Hello. New forum member here. Glad to join. I recently purchased a 2005 XC90 2.5T AWD from my best friends fiancés parents. They bought it new. It has 122K miles and is in great shape. When I bought it had the CEL and SRS urgent lights on. The SRS service urgent is on because someone put Bluetooth in without disconnecting Neg bat terminal. I’ve heard if I can find someone with vida/dice they can shut it off for me. Ok, here’s what really matters. I have a OBD2 scanner and it’s showing P0088 mostly and occasionally P0090 and P0101. I clear it and almost immediately when it’s idling it throws a P0088 fuel system pressure too high. I bought a Bosch FPS and replaced the old one and that did nothing. No change. The P0090 is making me believe the PEM unit might be faulty. Or maybe the wiring from the PEM. Maybe the wiring from the FPS. I’m going to change the Fuel filter and take pressure readings from the rail and the filter shrader valves. Anybody have any thoughts on this problem?? Also it drives great except it goes through gas horribly. 10 miles per gallon. At idle I can hear and feel a split second stumble in rpm. It seems as if the pressure is spiking during idle and starting. I also cleaned the MAF properly with crc MAF cleaner. I’m at a loss and don’t want to keep throwing money at it. I’m willing to try a used PEM if that’s the case.

voltech1 · Post by **voltech1** » 14 Dec 2018, 22:52

You are on the right track. The fuel pressure reading is too high. Check the rail pressure and if it corresponds to the scanner it's the PEM or circuit.

johnboy77 · Post by **johnboy77** » 17 Dec 2018, 21:36

I took pressure measurements and the rails pressure was 85psi at start up an slowly drops to 66-75 at idle. The valve next to the fuel filter showed 65-70 constant. I changed the fuel filter and found that the PEM was next to it. I took the PEM apart and found 3 tablespoons of white powder inside. The aluminum heat shrink had corroded inside the PEM. I dump it out and put it back and no changes. Still throwing CEL P0088,P0090, P0101. When you say check the circuit how exactly can I do that?? Can use my multimeter in anyway to test volts?? Going to FPS? PEM? MAF?? New PEM cost$350, used ebay one $85 with 1 year warranty. Which is better deal??

johnboy77 · Post by **johnboy77** » 24 Dec 2018, 03:00

SOLVED: PEM unit was bad. Swapped out for a good one and all’s good now.

Post by **abscate** » 24 Dec 2018, 05:20

If you searched the PEM part number you would find thethreadbyshockeave with links to the PEM waveforms and voltages from an earlier thread.

That corrosion takes out thePEM, it might pay for people to clean them out on a 10 year interval?

johnboy77 · Post by **johnboy77** » 31 Dec 2018, 14:18

I was able to fix all this by putting a used PEM unit in. Cleared everything right up.

Post by **ggleavitt** » 31 Dec 2018, 14:49

You still have this PEM? Any chance you can take the board off and get some photos of the interface(s) between the PCB, the pad and the heat sink? I'm doing some digging on PEMs, this one almost looks like a bad interface between the thermal pad that has experienced galvanic corrosion. No big deal if you no longer have it, just thought to ask.

Post by **abscate** » 07 May 2019, 09:37

The aluminum heat sink above the circuit board flakes off and drops onto the board , shorting it out, if you cleaned it out and applied a conformal coating on the board, that would fix it. I managed to rejuvenate my PEM with contact cleaner, and it worked in the car until my new one came. I went new because this car takes 500 mile business trips with clients, and it has been so damn cheap to own I gave it its due,