DTC P0088. GMC Truck GMC T-Series Medium Duty Truck F6/F7/F8 2007

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 2007 🢒 GMC T-Series Medium Duty Truck F6/F7/F8 🢒 DTC 🢒 DTC P0088

Circuit Description

The engine control module (ECM) monitors fuel rail pressure (FRP) using the FRP sensor. If the sensor indicates a pressure more than the commanded rail pressure, plus a possible transitional overshoot, the ECM will set DTC P0088 for fuel rail pressure too high.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0088 Fuel Rail Pressure (FRP) Too High

Conditions for Running the DTC

•	The engine coolant temperature (ECT) is between 30-100°C (86-212°F).

•	The fuel temperature is between 20-80°C (68-176°F).

•	The deviation of rail pressure is less than 5 MPa (725 psi).

•	The deviation of engine speed is less than 50 RPM.

•	The above conditions are met for 5 seconds.

•	The engine is running.

•	The battery voltage is between 10-16 volts.

Conditions for Setting the DTC

•	Commanded fuel supply is 0 mm³/stroke.

•	Actual fuel rail pressure is higher than desired pressure 10 MPa (1,450 psi).

•	The above conditions are met for 22 seconds.

Action Taken When the DTC Sets

•	The ECM illuminates the malfunction indicator lamp (MIL) and reduced engine power indicator lamp, if equipped, when the diagnostic runs and fails.

•	The ECM records the operating conditions at the time the diagnostic fails. The ECM stores this information in the Failure Records.

•	The ECM limits accelerator operating range.

•	The ECM limits fuel injection quantity.

•	The ECM limits fuel rail pressure.

•	The ECM closes the exhaust gas recirculation (EGR) valve and stops EGR control.

•	The ECM inhibits cruise control.

Conditions for Clearing the DTC

•	The MIL resets when the ignition is turned OFF.

•	A current DTC, Last Test Failed, clears when the diagnostic runs and passes.

•	Clear the MIL and the DTC with a scan tool.

Diagnostic Aids

Important: The Actual Fuel Rail Pressure on the scan tool will only update with the engine running or one time after the key is cycled when the ignition has been turned OFF for more than 10 seconds.

•	An intermittently sticking suction control valve (SCV) may have allowed the fuel pressure to become high enough to set this DTC.

•	Normal actual fuel rail pressure readings on the scan with the engine running Park or Neutral at idle are 25-35 MPa (3,650-5,050 psi) and 60-130 MPa (8,700-18,850 psi) in Park or Neutral at WOT, accelerator pedal full travel.

•	A skewed FRP sensor value, shifted to a higher pressure, can set this DTC. The actual fuel rail pressure on the scan tool should read 0 MPa (0 psi) with the key ON and the engine OFF after the engine has stopped running for a minimum of 2 minutes.

•	Resistance in the FRP sensor low reference circuit can set this DTC. Ensure that the sensor low reference circuit has no resistance and the connectors are tight and free of corrosion.

Step

Action

Values

Yes

Schematic Reference: Engine Controls Schematics

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

Observe the Failure Records for this DTC.
Turn OFF the ignition for 30 seconds.
Start the engine.
Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

Go to Step 3

Go to Intermittent Conditions

Clear the DTC.
Bleed the air from fuel system.
Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

Go to Step 13

Go to Step 4

Perform the fuel system diagnosis.
Inspect for a poor connection at the fuel rail pressure sensor.
If a condition is found, repair as necessary.

Was a condition found?

Go to Step 13

Go to Step 5

Test the signal circuit between the engine control module (ECM) and the fuel rail pressure sensor for the following conditions:

•	An open or short to ground

•	An open or short to battery voltage

Repair the circuits, as necessary.

Did you find and correct the condition?

Go to Step 10

Go to Step 6

Wait 2 minutes for the fuel pressure to bleed down from the fuel rail.
Turn ON the ignition, with the engine OFF.
Observe the Actual Fuel Pressure parameter with a scan tool.

Is the fuel parameter near the specified value?

0 MPa

Go to Step 7

Go to Step 9

Bleed the air from the fuel system.
Start the engine.
Observe the Actual Fuel Pressure parameter with a scan tool.

Is the parameter within the specified range?

25-40 MPa (3,626-5,801 psi)

Go to Step 8

Go to Step 9

Bleed the air from the fuel system.
Inspect the DTC.
Inspect the fuel pressure.

Was a condition found?

Go to Step 12

Go to Step 11

Replace the fuel rail assembly.

Did you complete the replacement?

Go to Step 13

Review the DTC.

Inspect the DTC with the scan tool.
Clear the DTC.
Bleed the air from the fuel system.
Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Is the DTC current?

Go to Step 11

Go to Step 13

Replace the supply pump assembly.

Did you complete the replacement?

Go to Step 13

Important: The replaced ECM must be programmed.

Replace the ECM. Refer to, Engine Control Module Replacement/Restore Fuel Rate Data , and Fuel Injector Flow Rate Programming .

Did you complete the replacement?

Go to Step 13

Clear the DTCs with a scan tool.
Turn OFF the ignition for 30 seconds.
Start the engine.
Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

Go to Step 2

Go to Step 14

Observe the Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?

Go to Diagnostic Trouble Code (DTC) List - Vehicle

System OK