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Home >> GMC >> 2006 >> Sierra 1500 HD, RWD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 25 (ENGINE CONTROLS - 6.6L - DIAGNOSIS (DTCs P0016-P0401)) >> DTC P0090 >> Test Description

Test Description

WARNING: This page is about a different variant/trim than selected.

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

  1. 7:  This step tests for battery voltage through the ECM to the FRP regulator.
  2. 8:  This step tests for an open control circuit between the ECM and the FRP regulator.
  3. 9:  This excessive current code can be set by voltage being applied between the ECM and the FRP regulator on the FRP control circuit.
DTC P0090

Step Action Values Yes No
Schematic Reference: Engine Controls Schematics
Connector End View Reference: Engine Control Module (ECM) 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
2 Is DTC U0105 present also? - Go to DTC U0100-U0299 (Diesel Engine) or DTC U0100-U0299 (HP2) Go to Step 3 
3
    IMPORTANT: Failure to wait until there is no engine control module (ECM) communications with the scan tool will result in misdiagnosis.
  1. Turn OFF the ignition for 30 seconds.
  2. Turn ON the ignition, with the engine OFF.
  3. Observe the FRP Regulator Command parameter with a scan tool.
Is the FRP Regulator Command more than the specified value?		 20% Go to Step 4  Go to Step 20 
4 Attempt to start the engine.
Does the engine start?		 - Go to Step 5  Go to Step 6 
5
  1. Start the engine.
  2. Observe the Actual Fuel Rail Pressure and the Desired Fuel Rail Pressure with a scan tool.
Does the scan tool display a pressure difference more than the specified value?		 5 MPa Go to Step 7  Go to Diagnostic Aids 
6
  1. Turn OFF the ignition.
  2. Disconnect the ECM connectors.
  3. Disconnect the fuel rail pressure (FRP) regulator connector.
  4. Measure the resistance from the control circuit of the FRP regulator to ground with a DMM.
Does the resistance measure at the specified value?		 infinity Go to Step 17  Go to Step 14 
7
  1. Turn OFF the ignition.
  2. Disconnect the FRP regulator harness connector.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the supply circuit of the fuel rail pressure regulator with a J 35616-200  12-volt unpowered test lamp connected to a good ground. Refer to Troubleshooting with a Test Lamp .
Does the test lamp illuminate?		 - Go to Step 8  Go to Step 10 
8
  1. Turn OFF the ignition.
  2. Verify the FRP regulator harness connector is disconnected.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the control circuit of the FRP regulator with a J 35616-200  connected to battery voltage. Refer to Troubleshooting with a Test Lamp .
Does the test lamp illuminate?		 - Go to Step 15  Go to Step 9 
9
  1. Disconnect the ECM connector containing the FRP regulator control circuit.
  2. Turn ON the ignition, with the engine OFF.
  3. Measure the voltage from the FRP regulator control circuit to a good ground with a DMM.
Does the voltage measure the specified value?		 0 V Go to Step 18  Go to Step 13 
10
  1. Turn OFF the ignition.
  2. Disconnect the ECM.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the ignition 1 voltage circuit of the harness connector with a J 35616-200  that is connected to a good ground. Refer to Troubleshooting with a Test Lamp .
Does the test lamp illuminate?		 - Go to Step 11  Go to Step 12 
11
  1. Test for an open in the FRP supply circuit between the ECM and the FRP regulator.
  2. If a condition is found, repair as necessary. Refer to Wiring Repairs .
Did you find and correct the condition?		 - Go to Step 21  Go to Step 19 
12 Repair the open in the ignition 1 voltage circuit to the ECM. Refer to Wiring Repairs .
Did you complete the repair?		 - Go to Step 21  -
13 Repair the short to voltage in the control circuit between the ECM and the FRP regulator. Refer to Wiring Repairs .
Did you complete the repair?		 - Go to Step 21  -
14 Test for a short to ground in the control circuit between the ECM and the FRP regulator. Refer to Wiring Repairs .
Did you find and correct the condition?		 - Go to Step 21  Go to Step 20 
15 Test the ignition voltage, fuel pressure regulator solenoid command, and fuel pressure regulator solenoid supply voltage circuits for high resistance. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?		 - Go to Step 21  Go to Step 16 
16
  1. Test for an intermittent and for a poor connection at the FRP regulator. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .
  2. Repair the wiring, as necessary. Refer to Wiring Repairs .
Did you find and correct the condition?		 - Go to Step 21  Go to Step 17 
17 Replace the FRP regulator. Refer to Fuel Injection Pump Replacement .
Did you complete the replacement?		 - Go to Step 21  -
18 Test for an open in the control circuit between the ECM and the FRP regulator. Refer to Wiring Repairs .
Did you find and correct the condition?		 - Go to Step 21  Go to Step 19 
19
  1. Inspect for poor connections at the ECM. Refer to Testing for Intermittent Conditions and Poor Connections .
  2. Repair the wiring, as necessary. Refer to Wiring Repairs .
Did you find and correct the condition?		 - Go to Step 21  Go to Step 20 
20 Replace the ECM. Refer to Control Module References for replacement, setup, and programming.
Did you complete the replacement?		 - Go to Step 21  -
21
  1. Clear the DTCs with the 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 22 
22 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
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