2002 LB7. So I’m getting these two codes high pressure and fuel pressure circuit. I replaced the FPR because my research lead me in this direction, it however did not fix it. So I started looking at the wiring to the FPR and at some point it was spliced and replaced, so I stripped it back at the ECM and trying to read voltage on either of the lines when I run the engine, and I’m not seeing any voltage. Could a bad fuel pressure sensor be my problem? And how do I test the sensor, what resistance should it read?
P0090 And P0088
- Thread starter Appletreedude
- Start date
Does the truck start? Reading the FSM for diagnosing this says if you have a P0088 and a P0090, follow the diagnostic steps for the P0090. Basic diagnosis there requires a scan tool, key on with engine off should have < 20% for the FPR regulator command. After that, it's wiring checks. Unplug the FPR, there should be 12v on pin 1 supplied by the ECM (purple/white on the 03) with key on.
The 2nd pin on the FPR is the control signal from the ECM, there is no resistance spec, but the ECM expects the current in this circuit to be between 50-1600mA. Pull the ECM connectors and the FPR connector, check for short to ground on this circuit.
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The Truck does start. I checked voltage on the purple/white wire at the ECM. 0 volts key off, 0.2 Volts key on, and it goes to a maximum of 0.6 volts when the engine is running. There is no ground on either wire from the ECM to the FPR. This is with the wires disconnected at the ECM, next I’ll reconnect the wires and check again, but I don’t expect to see anything different, I can’t see why the voltage would change. If I’m not getting 12 volts, what’s next? is the ECM is bad?
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The ECM supplies +12v to the FPR, if you're only measuring 0.2-0.6v on the FPR connector with the FPR disconnected, that means the ECM isn't supplying the voltage or there's an open connection in the harness somewhere between the ECM output to the FPR. I am not sure I 100% followed your description, and be aware that I'm following my '03 schematics, I don't have copies of the '02.
Tell me where things go wierd, these are the FSM debug steps, in order.
- Disconnect the FRP regulator connector. Turn on the ignition, measure the +12 supply (purple/white) at this connector. Should be +12v. If no, go to step 2.
- With ignition off, unplug connector C2 from the ECM. Turn on ignition, probe "Ignition 1" voltage in the C2 connector. This is pin 44 (pink wire) in my '03 manual. If there is +12v here, go to step 3. If not, check the ECMRPCV fuse which supplies this circuit.
- Look for an open on the +12v supply between the ECM and the FRP regulator.
appletreedude, what ended up being your issue? I am having the exact same issue with my truck and cannot figure it out !
Last on the forum Nov '19. I wouldnt hold my breath waiting for a reply. That guy will never be back.
I kinda figured that, would you be able to help me ?
I have all the same issues as the appletree Dude
When I test the purple white wire at the FPR I get 7 volts. When I test the pink wire on c2 I get nothing
no Voltage.
Not sure what to do from here ?
I have all the same issues as the appletree Dude
When I test the purple white wire at the FPR I get 7 volts. When I test the pink wire on c2 I get nothing
no Voltage.
Not sure what to do from here ?
I also checked resistance between the ecm& FPR on the purple white wire as well as the yellow wire
Both check out good!
also the ecmrpv fuse is good!
Both check out good!
also the ecmrpv fuse is good!
What year is your truck? Please fill out your profile or otherwise provide more detail so we can try to help.
Sorry the truck is a 2002 lb7 crew cab truck
I don’t know much history of the truck
I just purchased it
You need to be seeing +12v at the FPR on the purple/white wire. This power comes from the ECM. There are connections in between the ECM and the FPR. Suggest tracing this back systematically to the ECM source.
Even though the FPR purple/white wiring seems to be the same on all LB7s, as mentioned in post #4, the pink wire for Ignition 1 power to the ECM came from looking at the 03 LB7 schematics - 01/02 may be different. I don't have the early schematics, perhaps someone would post up a picture of that circuit for the early LB7s.
Even though the FPR purple/white wiring seems to be the same on all LB7s, as mentioned in post #4, the pink wire for Ignition 1 power to the ECM came from looking at the 03 LB7 schematics - 01/02 may be different. I don't have the early schematics, perhaps someone would post up a picture of that circuit for the early LB7s.
So I tested for +12v at the FPR connector with key on and only came up with 7.6 v
Batteries reading 12.6 volts.
I also tested the pink wire on connector c2 but there was no voltage there at all (as you stated it might be different from the 03 schematics)
Hopefully someone will post a picture of the 02 wiring
I will trace the purple/ white wire back to the ecm