GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2005 🢒 TopKick C-Series (Conventional) C4/C5 🢒 Restraints 🢒 SIR 🢒 DTC P0087

Circuit Description

The engine control module (ECM) monitors fuel rail pressure (FRP) using the FRP sensor. If the sensor indicates a pressure less than the commanded rail pressure plus a possible transitional overshoot, the ECM will set DTC P0087 for fuel rail pressure too low.

DTC Descriptors

This diagnostic procedure supports the following DTC:

DTC P0087 Fuel Rail Pressure (FRP) Too Low

Conditions for Running the DTC
    • DTCs P0192, P0193, P0642 or P0643 are not set.
    • The ignition is ON.

Conditions for Setting the DTC

The actual FRP is less than 0.0 MPa at 0-400 RPM.

OR

The actual FRP is less than 22.5 MPa at more than 600 RPM.

Action Taken When the DTC Sets
    • 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.
    • The ECM will limit fuel injection.

Conditions for Clearing the MIL/DTC
    • 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.
    • Clear the MIL and the DTC with a scan tool.

Diagnostic Aids
    • A restricted fuel supply line may cause DTCs P0087 and P1093 to set at the same time. When ambient temperatures are below 0°C (32°F), the fuel tank pickup screen may be iced over from water in the fuel tank. Refer to Fuel System Diagnosis .
    • If power enhancing devices have been attached to the fuel rail pressure sensor circuits, this DTC may set and adversely effect the fuel system components. Refer to Fuel System Diagnosis - High Pressure Side .

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. If the fuel temperature is high enough to set DTC P0168, the fuel may be thin enough to cause this DTC to set.

    2.

  2. The engine will not start if the fuel leak is large enough.

    3.

  3. This step tests for fuel leaks into the engine oil.

    4.

  4. This step tests for an inaccurate fuel rail pressure sensor.

  5. This step tests for a restriction in the fuel system between the fuel injection pump and the fuel tank.

    6.

  6. This test tests to see if the fuel injection pump is able to supply maximum fuel pressure at idle. The fuel injection pump should be able to create 145-158 MPa at idle. In extreme ambient or fuel temperatures, the fuel injection pump may only be able to generate a pressure at the low end of this range.

    7.

  7. This step tests for a restriction in the fuel system between the fuel injection pump and the fuel tank that may only cause symptoms at higher engine speed and load conditions.

    8.

  8. This step tests to see if the fuel rail pressure sensor wiring and ECM are functioning normally.

    9.

  9. If the vacuum is still too high in the fuel supply system after replacing the fuel filter, there is a restriction in the fuel supply lines or sending unit in the fuel tank.

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 - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2

Is DTC P0168 or DTC P0090 also set?

--

Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information

Go to Step 3

3

Attempt to start the engine.

Does the engine start and idle?

--

Go to Step 4

Go to Engine Cranks but Does Not Run

4
  1. Observe the Freeze Frame/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 5

Go to Diagnostic Aids

5

  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 6

Go to Step 10

6

Inspect the engine oil for fuel contamination. Refer to Fuel in Engine Oil in Engine Mechanical.

Did you find and correct the condition?

--

Go to Step 17

Go to Step 7

7

  1. Install the J 44638 Vacuum Gage on the fuel fitting located on the right side front of the engine.
  2. Start and run the engine at idle.
  3. Observe the vacuum gage while increasing RPM slowly to wide open throttle (WOT) in Park or Neutral.

Does the vacuum measure less than the specified value through the entire RPM range?

5 in

Go to Step 8

Go to Step 11

8

  1. Start and idle the engine until the idle speed drops to 680 RPM.
  2. Command the fuel pressure control to 160 MPa with a scan tool.
  3. Observe the Actual Fuel Rail Pressure parameter with a scan tool.

Is the Actual Fuel Rail Pressure parameter more than the specified value?

145 MPa

Go to Step 9

Go to Fuel System Diagnosis - High Pressure Side

9

Important: If the fuel temperature is near 121°C (250°F) during the duplication of the complaint, or in the Failure Records for this DTC, inspect for a restriction in the fuel cooler air flow or the fuel heater always ON. Refer to Fuel Heater Always On .

Operate the vehicle within the conditions for which the customer complaint occurs.

Does the vacuum measure less than the specified value through the entire operating range?

12 in

Go to Diagnostic Aids

Go to Step 11

10

  1. Disconnect the fuel rail pressure sensor. Refer to Fuel Injection Fuel Rail Fuel Pressure Sensor Replacement .
  2. Observe the Actual Fuel Rail Pressure with a scan tool.

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

175 MPa

Go to Step 15

Go to Step 14

11

Replace the fuel filter. Refer to Fuel Filter Replacement .

Did you compete the replacement?

--

Go to Step 12

--

12

  1. Ensure that the J 44638 is still installed on the engine.
  2. Start and run the engine under the conditions for which the high vacuum occurred.

Does the vacuum measure less than or equal to the specified value?

5 in at idle or 12 in at high speed

Go to Step 17

Go to Step 13

13

Repair the restriction in the fuel supply lines between the fuel tank and the fuel injection pump. Refer to Fuel System Diagnosis .

Did you complete the repair?

--

Go to Step 17

--

14

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

Did you find and correct the condition?

--

Go to Step 17

Go to Step 16

15

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

Did you complete the replacement?

--

Go to Step 17

--

16

Replace the engine control module (ECM). Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the replacement?

--

Go to Step 17

--

17
  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 18

18

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 in Vehicle DTC Information

System OK