GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2002 🢒 GMC C Sierra - 2WD 🢒 Engine 🢒 Engine Controls - 6.6L 🢒 DTC P0089

Circuit Description

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.

Conditions for Running the DTC
    • DTCs P0192, P0193, or P1635 are not set.
    • The ignition is ON.

Conditions for Setting the DTC
    • The difference between actual and desired FRP is more than 20 MPa.
    • Commanded fuel pump flow is 100 mm³/second or less.

Action Taken When the DTC Sets - California
    • The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
    • The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.

Action Taken When the DTC Sets - Federal
    • The control module stores the DTC information into memory when the diagnostic runs and fails.
    • The malfunction indicator lamp (MIL) will not illuminate.
    • The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.
    • The driver information center, if equipped, may display a message.

Conditions for Clearing the MIL/DTC - California
    • The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
    • A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
    • A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
    • Use a scan tool in order to clear the MIL and the DTC.

Conditions for Clearing the DTC - Federal
    • A current DTC Last Test Failed clears when the diagnostic runs and passes.
    • A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
    • Use a scan tool in order to clear the DTC.

Test Description

The number below refers to the step number on the diagnostic table.

  1. DTC P0090 is a current flow problem in the FRP regulator circuit. This incorrect current draw could lead to incorrect fuel pressure. This hardware problem should be diagnosed before the performance DTC is checked.

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics

Connector End View Reference: Engine Control Module Connector End Views or Engine Controls Connector End Views

1

Did you perform the Diagnostic System Check-Engine Controls?

--

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2
  1. Turn ON the ignition, with the engine OFF.
  2. Observe the Actual Fuel Rail Pressure parameter with a scan tool.

Is the Actual Fuel Rail Pressure parameter within the specified range?

1-1.8 MPa

Go to Step 3

Go to Step 7

3

Did DTC P0090 also set?

--

Go to DTC P0090

Go to Step 4

4

Did DTC P1093 also set?

--

Go to DTC P1093

Go to Step 5

5
  1. Start and run the engine at 2,000 RPM.
  2. Observe the Actual Fuel Rail Pressure parameter and the Desired Fuel Rail Pressure parameter with a scan tool.

Is the fuel pressure difference more than the specified value?

20 MPa

Go to Step 11

Go to Step 6

6
  1. Start and idle the engine.
  2. Perform the following test at idle and at 2,000 RPM:
    3. 2.1. Change the fuel pressure with a scan tool, incrementing through the entire fuel pressure range.
    2.2. Observe the actual vs desired fuel pressures at each fuel pressure level.

Does the fuel pressure increment and stabilize through the entire fuel pressure range, with actual and desired fuel pressure within 2 MPa of each other at every fuel pressure?

--

Go to Intermittent Conditions

Go to Step 11

7
  1. Disconnect the fuel rail pressure sensor.
  2. Observe the Actual Fuel Rail Pressure parameter with a scan tool.

Does the Actual Fuel Rail Pressure measure more than the specified value?

175 MPa

Go to Step 10

Go to Step 8

8

Test the fuel rail pressure sensor signal circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 9

9

Replace the engine control module. Refer to Engine Control Module Replacement .

Did you complete the replacement?

--

Go to Step 12

--

10

Replace the fuel rail pressure sensor. Refer to Fuel Injection Fuel Rail Fuel Pressure Sensor Replacement .

Did you complete the replacement?

--

Go to Step 12

--

11

Replace the FRP regulator. Refer to Fuel Pressure Regulator Replacement .

Did you complete the replacement?

--

Go to Step 12

--

12
  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC.

Does the DTC fail this ignition?

--

Go to Step 2

Go to Step 13

13

With a scan tool, observe the stored information, Capture Info.

Does the scan tool display any DTCs that have not been diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List

System OK