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Old 02-05-2020, 09:04 PM   #1 (permalink)
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Help! FPR driving me crazy

Hey everyone, I have an 04 lb7. Brand new Bosch injectors, high pressure fuel lines. Problem is I got a p0089 after installation, and replaced the fpr and still getting p0089. I have an airdog and I have lowered the pressure at the pump and still have the same issue. The only time the p0089 sets is on deceleration. On decel the desired rail pressure is between 4.4-6.2kpsi and I’m getting up to 14kpsi actual. Acceleration is perfect desired and actual match amazing. At a stop the rail pressure lowers slowly to the correct pressure. No other codes!!! Cp3 is making great power. Truck is running incredible otherwise. I need some advice please?? Thanks guys

2004 LB7 Duramax
Airdog lift pump
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Old 02-06-2020, 09:00 AM   #2 (permalink)
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P0089; The engine control module (ECM) uses commanded fuel pump flow to determine a desired fuel rail pressure (FRP). The actual fuel pressure is monitored using the FRP sensor. If the FRP sensor indicates a pressure more than 20 MPa greater than desired, DTC P0089 will set.

1) Open or poor connections at the MPROP (FPR) connector-pigtail or main engine harness connector will cause loss of pressure control, maximum rail pressure at idle.
2) A stuck MPROP (FPR) can cause excessive rail pressure.
3) Bad suction valves in the high pressure pump can cause rail pressure to be excessive.
4) The ECM can fail and cause the rail pressure to increase beyond the desired amount.

You did buy OEM FPR? GM Part:97728979 Bosch Part :0928400535
You need to look at your installation Since that’s when it started.

Last edited by Rvn4me; 02-06-2020 at 09:21 AM.
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Old 02-06-2020, 04:44 PM   #3 (permalink)
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Assuming nothing funky has been done in the tuning you need to lower the pressure of the lift pump. Air Dog has had a ton of regulator issues.
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Old Yesterday, 11:13 AM   #4 (permalink)
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4 psi is enough for these trucks to get the fuel to the cp3. I don't know why anyone would want to see 12 psi that some of these lift pumps deliver. I use Kennedy lift pump and it just works like it should. No issues at all.
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