GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 Kodiak C-Series (Conventional) C6/C7/C8 🢒 Engine 🢒 Engine Controls - 7.8L 🢒 DTC P1087

Circuit Description

The fuel supply system comprises a fuel rail pressure sensor, a priming pump on the supply pump, and pipes. The fuel pressure sensor measures pressure of fuel rail. The fuel supply system sends signal to the engine control module (ECM).

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P1087 Fuel Rail Pressure (FRP) Limiter Active

Conditions for Running the DTC
    • The ignition switch is ON.
    • The battery voltage is between 10-16 volts.

Conditions for Setting the DTC
    • The rail pressure is more than 210 MPa (30,748 psi).
    • A pressure fall is carried out quickly.

Action Taken When the DTC Sets
    • The ECM illuminates the malfunction indicator lamp (MIL) and reduced engine power indicator lamp 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 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 become high enough to open the pressure limiter valve.
    • 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 shorted SCV or a short between the high and low control circuit will set DTC P1087 and may not set an electrical DTC P0091 or P0092.
    • An intermittently sticking fuel injector may have allowed the fuel pressure to drop too much. Use a scan tool to perform the Cylinder Power Balance Test for each injector. Verify a consistent engine speed change when commanding each fuel injector ON and OFF.
    • 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.
    • The fuel system from the fuel tank to the fuel supply pump is under a slight vacuum with the engine running. As a result, air can enter the fuel system if these connections are not tight or if there is a crack in one of the fuel hoses. Air in the fuel system will cause fuel rail pressure fluctuations especially at high engine speed and load, which may set this DTC.

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics

1

Did you perform the Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle

2
  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 Failure Records.

Does the DTC fail this ignition?

--

Go to Step 3

Go to Intermittent Conditions

3
  1. Clear the DTCs with a scan tool.
  2. Operate the vehicle under the conditions to set the DTC.

Did the DTC set?

--

Go to Step 4

System OK

4
  1. Perform the fuel system check.
  2. Inspect for a poor connection at the fuel rail pressure sensor.
  3. If a condition is found, repair, as necessary.

Was a condition found?

--

System OK

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

Inspect the fuel pipe.

  1. Stop the engine.
  2. Inspect the fuel line for damage and leakage.
  3. If a condition is found, repair or replace, as necessary.

Was a condition found?

--

System OK

Go to Step 7

7

Inspect the fuel injection state of an injector.

  1. Connect the scan tool.
  2. Turn ON the ignition.
  3. Clear the DTC.
  4. Perform the actuator test.
  5. Listen for engine noise.

Change the engine noise?

--

Go to Step 9

Go to Step 8

8

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

Is the action complete?

--

Go to Step 19

--

9
  1. Test the signal circuit between the engine control module (ECM) and the fuel rail pressure sensor for the following conditions:
    2. • An open or short to ground circuit
    • An open or short to battery voltage
  2. Repair the circuits, as necessary.

Did you find and correct the condition?

--

Go to Step 19

Go to Step 10

10
  1. Turn ON the ignition.
  2. Observe the engine data on display.

Is the fuel pressure value within the specified range?

0 MPa

Go to Step 11

Go to Step 13

11
  1. Start the engine
  2. Observe the engine data on display.

Is the fuel pressure value within the specified range?

24-40 MPa (3,626-5,801 psi)

Go to Step 12

Go to Step 13

12

Observe the fuel pressure in fuel rail.

  1. Bleed the air from the system.
  2. Run the vehicle under the conditions to set the DTC.
  3. Observe the fuel pressure.

Was a condition found?

--

Go to Step 13

Go to Step 11

13

Inspect the fuel rail pressure sensor.

Was a condition found?

--

Go to Step 17

Go to Step 14

14
  1. Turn ON the ignition.
  2. Inspect for fuel leakage on the fuel line.
  3. Turn OFF the ignition.
  4. Inspect the flow damper noise.

Was a condition found?

--

Go to Step 15

Go to Step 16

15
  1. Turn OFF the engine.
  2. Inspect the fuel pipe for leakage.

Did you find and correct the condition?

--

Go to Step 20

Go to Step 16

16
  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 17

Go to Step 18

17

Replace the fuel rail system assembly.

Is the action complete?

--

Go to Step 20

--

18

Review the DTC.

  1. Observe the DTC with the scan tool.
  2. Clear the DTC.
  3. Bleed the air from the fuel system.
  4. Perform the test, run, and review the DTC.

Is a DTC detected?

--

Go to Step 19

Go to Step 20

19

Important: The replacement 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 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