GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The fuel supply pump draws fuel from the fuel tank and pumps the high pressure fuel to the fuel rail. The quantity of the fuel discharged from the supply pump controls the pressure in the fuel rail. The suction control valve (SCV) in the fuel supply pump effects this control in accordance with the command received from the engine control module (ECM). The fuel pressure of the high pressure side is measured by the fuel rail pressure (FRP) sensor. If the ECM detects an excessively high FRP, this DTC will set.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P2921 Fuel Rail Pressure (FRP) Too High

Conditions for Running the DTC

    • The ignition is ON.
    • The battery voltage is between 10-16 volts.
    • The engine is running.
    • DTC P0192, P0193 is not set.

Conditions for Setting the DTC

The ECM detects that the fuel rail pressure is more than 230 MPa (33,350 psi) for 1 second.

Action Taken When the DTC Sets

    • The ECM illuminates the malfunction indicator lamp (MIL) and reduced engine power indicator lamp, if fitted, 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 fuel injection quantity for fail-safe operation.
    • The ECM limits fuel rail pressure for fail-safe operation.
    • The ECM closes the exhaust gas recirculation (EGR) valve and holds to close position.
    • The ECM inhibits the 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 malfunction indicator lamp (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.

    • A sticking suction control valve (SCV) may have allowed the fuel pressure 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 wide open throttle (WOT), accelerator pedal full travel.
    • A skewed fuel rail pressure (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

No

Schematic Reference: Engine Controls Schematics

1

Did you perform the Diagnostic System Check - Vehicle?

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Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. Install a scan tool.
  2. Start the engine.
  3. Monitor the DTC information with a scan tool.

Is DTC P0088, P0091, P0092, P0192, P0193, P0201-P0206, P1087, P1088, P1263-P1266, P2011, P2012, or P2921 also set?

--

Go to Diagnostic Trouble Code (DTC) List - Vehicle

Go to Step 3

3

  1. Turn OFF the ignition for 30 seconds.
  2. Place the transmission in Park or Neutral.
  3. Start the engine.
  4. Observe the Actual Fuel Rail Pressure parameter with a scan tool.
  5. Accelerate the engine between idle and wide open throttle (WOT), accelerator pedal full travel, many time while observing the scan tool.

Does the Actual Fuel Rail Pressure ever exceed the specified value?

230 MPa (33,350 psi)

Go to Step 4

Go to Diagnostic Aids

4

  1. Perform the fuel system check. Refer to Fuel System Diagnosis .
  2. If a condition is found, repair as necessary.

Did you find and correct the condition?

--

Go to Step 20

Go to Step 5

5

  1. Inspect the attachment state of a supply pump.
  2. If a condition is found, adjust as necessary.

Was a condition found?

--

System OK

Go to Step 6

6

  1. Inspect the fuel injection state of the injector.
  2. Connect the scan tool.
  3. Turn ON the ignition.
  4. Clear the DTC.
  5. Perform the actuator test.
  6. Listen for engine noise.

Is there a change in the engine noise?

--

Go to Step 8

Go to Step 7

7

Replace the injector. Refer to Fuel Injector Replacement and Fuel Injector Flow Rate Programming .

Did you complete the replacement?

--

Go to Step 20

--

8

  1. Observe the Failure Records for this DTC.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. 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 9

Go to Step 20

9

  1. Turn OFF the ignition.
  2. Wait 2 minutes for the fuel pressure to bleed down from the fuel rail.
  3. Turn ON the ignition with the engine OFF, do not start the engine.
  4. Observe the Actual Fuel Rail Pressure parameter with a scan tool.

Is the fuel pressure value at the specified value?

0 MPa

Go to Step 10

Go to Step 12

10

  1. Inspect the fuel pressure with the scan tool.
  2. Bleed the air from the fuel system.
  3. Start the engine.
  4. Observe the engine data on the display.

Is the fuel pressure value within the specified range?

25-40 MPa

Go to Step 13

Go to Step 11

11

  1. Start the engine.
  2. Observe the actual fuel rail pressure with a scan tool.
  3. Bleed the air from the fuel system.
  4. Clear the DTCs.
  5. Observe the actual fuel rail pressure within a scan tool.

Was a condition found?

--

Go to Step 15

Go to Step 12

12

Inspect the fuel rail pressure (FRP) sensor.

Was a condition found?

--

Go to Step 15

Go to Step 19

13

  1. Observe the Failure Records for this DTC.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. 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 14

Go to Step 20

14

  1. Bleed the air from the fuel system.
  2. Start the engine.
  3. Compare the Actual Fuel Rail Pressure and Desired Fuel Rail Pressure parameters with a scan tool.
  4. Operate the accelerator pedal slowly while observing the Actual Fuel Rail Pressure and Desired Fuel Rail Pressure parameters.

Did the actual fuel rail pressure follow closely to desired fuel rail pressure through the entire operating range?

--

Go to Step 15

Go to Step 16

15

Replace the fuel rail assembly.

Did you complete the replacement?

--

Go to Step 20

--

16

  1. Observe the Failure Records for this DTC.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. 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 17

Go to Step 20

17

Replace the supply pump. Refer to Fuel Injection Pump Replacement .

Did you complete the replacement?

--

Go to Step 18

--

18

  1. Bleed the air from the fuel system.
  2. Clear the DTCs with a scan tool.
  3. Turn OFF the ignition for 30 seconds.
  4. Start the engine.
  5. 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 19

Go to Step 20

19

Important: The new engine control module (ECM) must be programmed.

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

Did you complete the replacement?

--

Go to Step 20

--

20

  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. 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 21

21

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