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Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1144 (Engine Controls Diagnosis - 6.0L - Alternative Fuels (DTC P0005-DTC P2665)) >> Diagnosis >> DTC P0191: Fuel Rail Pressure Sensor Performance >> Test Description

Test Description

WARNING: This page is about a different car, the 2004 GMC Sierra and 2004 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.

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

  1. 2:  This step determines if the condition is present.
  2. 4:  This step determines if the low pressure lock-off (LPL) solenoid is functioning.
  3. 5:  This step tests the low reference circuit of the FRP sensor.
  4. 6:  This step determines if the 5-volt reference circuit is the cause of the condition. The DMM should display 5.0 volts across the test lamp.
  5. 7:  This step tests the signal circuit of the FRP sensor.
  6. 9:  This step verifies that a mechanical fuel system condition is not the cause of the concern. A fuel pressure regulator condition may cause this DTC to set.
DTC P0191

Step Action Values Yes No
Schematic Reference: Engine Controls Schematics
Connector End View Reference: Engine Controls Connector End Views
1 Did you perform the Diagnostic System Check Alternative Fuels - Engine Controls? - Go to Step 2  Go to Diagnostic System Check - Alternative Fuels (Engine Controls)
2 
  1. Turn ON the ignition, with the engine OFF.
  2. Observe the Fuel Rail Pressure (FRP) data display with a scan tool.
Does the scan tool display the FRP sensor pressure within the specified range?		 206-1 620 kPa (30-90 psi) Go to Step 3  Go to Step 4 
3
  1. Observe the Freeze Frame and/or the Failure Records data for this DTC.
  2. Turn the ignition OFF 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 and/or the Failure Records data.
Does the DTC fail this ignition cycle?		 - Go to Step 4  Go to Intermittent Conditions
4 
  1. Turn ON the ignition, with the engine OFF.
  2. Command the low pressure lock-off (LPL) ON and OFF with a scan tool.
  3. Listen for operation of the LPL.
Can operation of the LPL be heard?		 - Go to Step 5  Go to DTC P2665 
5 
  1. Disconnect the FRP sensor. Refer to Fuel Rail Pressure (FRP) Sensor Replacement .
  2. Probe the low reference circuit of the FRP sensor with a test lamp connected to B+.
Is the test lamp illuminated?		 - Go to Step 6  Go to Step 10 
6 
  1. Probe the 5-volt reference circuit of the FRP sensor with a test lamp to ground.
  2. Measure the voltage drop across the test lamp with a DMM. Refer to Measuring Voltage Drop in Wiring Systems in the C/K Pickup Service Manual.
Is the voltage at the specified value?		 5 V Go to Step 7  Go to Step 11 
7 
  1. Connect a 3-amp fused jumper wire between the signal circuit and the 5-volt reference circuit of the FRP sensor.
  2. Observe the FRP sensor data display with a scan tool.
Does the scan tool display FRP sensor voltage more than the value specified?		 4.95 V Go to Step 9  Go to Step 8 
8 Test the signal circuit of the FRP sensor for an open or excessive resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems in the C/K Pickup Service Manual.
Did you find and correct the condition?		 - Go to Step 15  Go to Step 12 
9 
IMPORTANT: Return to this diagnostic procedure, after performing the Fuel System Diagnosis.
Perform the Fuel System Diagnosis procedure. Refer to Fuel System Diagnosis .Did find and correct the condition?		 - Go to Step 15  Go to Step 13 
10 Test the low reference circuit of the FRP sensor for an open or excessive resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems in the C/K Pickup Service Manual.
Did you find and correct the condition?		 - Go to Step 15  Go to Step 12 
11 Test the 5-volt reference circuit of the FRP sensor for excessive resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems in the C/K Pickup Service Manual.
Did you find and correct the condition?		 - Go to Step 15  Go to Step 12 
12 Inspect for proper terminal contact at the harness connector of the powertrain control module (PCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems in the C/K Pickup Service Manual.
Did you find and correct the condition?		 - Go to Step 15  Go to Step 14 
13 Replace the FRP sensor. Refer to Fuel Rail Pressure (FRP) Sensor Replacement .
Did you complete the replacement?		 - Go to Step 15  -
14 Replace the PCM. Refer to Powertrain Control Module (PCM) Replacement in the C/K Pickup Service Manual.
Did you complete the replacement?		 - Go to Step 15  -
15
  1. Observe the Freeze Frame/Failure Records for this DTC.
  2. Turn OFF the ignition for 30 seconds.
  3. Turn ON the ignition, with the engine OFF.
  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 16 
16 Observe the Capture Info with a scan tool.
Are there any DTCs that have not been diagnosed?		 - Go to Diagnostic Trouble Code (DTC) List System OK
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