For 1990-2009 cars

# Lack of Power, Engine Will Not Rev-up, Idle Vibration, Engine Starting Concerns, DTCs P1093, P0087, P1087, P0088 and/or P1088 Set (Diagnose and Replace Suction Control Valve (SCV) (FPR), if Necessary)

Subject: | Lack Of Power, Engine Will Not Rev-up, Idle Vibration, Engine Starting Concerns, DTCs P1093, P0087, P1087, P0088 and/or P1088 Set (Diagnose and Replace Suction Control Valve (SCV) (Fuel Pressure Regulator (FPR)), if Necessary)

Models: | 2005-2007 Chevrolet W-Series Medium Duty Tilt Cab Models

| 2005-2007 GMC W-Series Medium Duty Tilt Cab Models

| 2005-2007 Isuzu NPR/NQR/NRR Commercial Models

| with 5.2L 4HK1-TC Diesel Engine

| 2004-2007 Chevrolet T6500-T8500, C6500-C8500 Series Medium Duty Models

| 2004-2007 GMC T6500-T8500, C6500-C8500 Series Medium Duty Models

| 2004-2007 Isuzu FTR/FVR/FXR/HTR/HVR/HXR Commercial Models

| with 7.8L Diesel Engine (RPO CTF)

### Condition

Some customers may comment on one or more of the following conditions:

• | Lack of power

• | Engine will not rev-up

• | Idle vibration

• | Engine starting concerns

• | DTCs P1093, P0087, P1087, P0088 and/or P1088

### Cause

One possible cause for this condition may be intermittent operation of the suction control valve (SCV) (fuel pressure regulator (FPR)).

### Correction

The following diagnostic and repair procedures are provided to better diagnose and, if necessary, replace the SCV (FPR).

Step | Description | YES | NO
--- | --- | --- | ---
1 |

1. Confirm the customer concern.
2. Using a scan tool, check the ECM for DTC(s).
3. Record the supply pump learn correction value.

Are any DTCs stored?

Go to Step 2

Go to Step 3

2 | Is the stored DTC listed below?

• | P1093

• | P0087

• | P1087

• | P0088

• | P1088

Go to Step 3

Follow diagnosis listed in appropriate service information

3 | Inspect the fuel system for the following conditions:

• | Restricted fuel filter

• | Aftermarket fuel filter

• | Fuel maintenance status

• | Air intrusion

• | Fuel quality/contamination

Was any above condition found?

Repair condition and retest vehicle operation

Complete Pressure Tests in steps 4, 5 and 6

4 | Pressure Stability Test #1

1. Start the vehicle. Allow the engine coolant to reach operating temperature of 70°C (158°F) or greater.
2. Monitor the fuel rail pressure (Actual, Designed) while the engine is idling.

Are the actual and desired fuel rail pressures greater than 5 MPa from one another?

Record the test result and go to Step 5.

Fail test #1

Pass test #1

5 | Pressure Tracking Test #2 While in Park, momentarily press the accelerator pedal to WOT and OFF repeatedly and monitor both actual and desired rail pressures. Does the actual pressure follow the desired without delay? Also rising pressure to high pressure area?

Record test result and go to Step 6.

Pass test #2

Fail test #2

6 | Pressure Overshoot/Undershoot Test #3 Test drive the vehicle and monitor the actual vs. desired fuel rail pressure. While driving at a steady speed, check "Actual" pressure reading. Actual pressure may excessively exceed desired pressure (overshoot) or fall far below desired pressure (undershoot).

Is there any sign of an overshoot or undershoot condition?

Record test results and go to Step 7.

Fail test #3

Pass test #3

7 | Did this vehicle fail more than one of the three pressure tests from steps 4-6? | Replace SCV (FPR) | Continue with DTC diagnostic

### Procedure

1. Tilt the cab and secure in place.
2. Disconnect the battery negative (Earth) cable.
3. Locate the SCV (FPR) on the Supply Pump on the left (driver) side of the engine.
4. Clean the location thoroughly to remove all dirt, debris and dust.
5. Disconnect the electrical connector from the SCV (FPR).
6. Remove the two mounting bolts and discard the bolts. New bolts are provided with the service kit.
7. Carefully remove the SCV (FPR). Inspect the FPR to be sure both O-rings remained with the valve. If the O-rings are not with the valve, remove from the supply pump.
8. Inspect the replacement SCV (FPR) for any dust or debris and carefully clean as necessary.
9. Carefully install new SCV (FPR) into the supply pump. Push the valve firmly until the valve seats completely into the supply pump.
10. Install two new mounting bolts for the SCV (FPR) and tighten to specification.

Tighten
Tighten the bolts to 6.9-10.8 N·m (61-95 lb in).

11. Connect the SCV (FPR) electrical connector.
12. Connect the battery negative (Earth) cable.
13. Start the vehicle and confirm vehicle operation.

### Parts Information

#### For Chevrolet and GMC Models

Part Number | Description
--- | ---
98043686 | SCV Kit (4HK1) (includes SCV, bolts and O-rings)
98043735 | SCV Kit (6HK1) (includes SCV, bolts and O-rings)

#### For Isuzu Models

Part Number | Description
--- | ---
8-98043-686-0 | SCV Kit (4HK1) (includes SCV, bolts and O-rings)
8-98043-735-0 | SCV Kit (6HK1) (includes SCV, bolts and O-rings)

Parts are to be obtained from AIPDN.

### Warranty Information

For vehicles repaired under warranty, use:

Labor Operation | Description | Labor Time
--- | --- | ---
J7806* | Replace Suction Control Valve (SCV) (Fuel Pressure Regulator (FPR)) | 0.2 hr
*This labor operation number is for bulletin use only. This number will not be published in the Labor Time Guide.