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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 1022 (Engine Controls Diagnosis - 6.6L (Lb7) (DTCS P0612 To P2141)) >> Diagnosis >> DTC P0651 >> Test Description

Test Description

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

The number below refers to the step number on the diagnostic table.

  1. 8:  If the circuit is shorted to the transmission control module (TCM) MIL request circuit, the scan tool will show skewed BARO and BOOST sensor readings just after the ignition is turned ON. The sensor readings will then return to normal in under 1 second.
DTC P0651

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-Engine Controls? - Go to Step 2  Go to Diagnostic System Check - Engine Controls
2
  1. Observe the Freeze Frame/Failure Records data 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.
Does the DTC fail this ignition?		 - Go to Step 3  Go to Intermittent Conditions
3
  1. Turn OFF the ignition.
  2. Disconnect the BARO sensor.
  3. Turn ON the ignition, with the engine OFF.
  4. Using a DMM, measure voltage between the 5-volt reference circuit of the BARO sensor and a good ground.
Is the voltage within the specified range?		 4.8 - 5.2 V Go to Step 5  Go to Step 4 
4 Does the voltage measure more than the specified value? 5.2 V Go to Step 8  Go to Step 6 
5
  1. Reconnect BARO sensor.
  2. Disconnect the APP sensor.
  3. Using a DMM, measure voltage between the 5-volt reference circuit of APP sensor 2 and the engine ground.
Is the voltage within the specified range?		 4.8 - 5.2 V Go to Intermittent Conditions Go to Step 9 
6
  1. Monitor DMM while disconnecting all other devices connected to the 5-volt reference circuit, one at a time. Refer to Engine Controls Component Views .
  2. If voltage changes when one of the devices are disconnected, replace the component. Refer to the appropriate replacement procedure below:
Was a component replaced?		 - Go to Step 11  Go to Step 7 
7
  1. Turn OFF the ignition.
  2. Disconnect the ECM.
  3. Test the 5-volt reference circuit for the following conditions. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
    • A short to ground
    • A short to any low reference circuit
    • A short to the fuel pressure regulator control circuit
    • A short to the TCM MIL request circuit
    • A short to the PCM MIL request circuit
    • A short to the ignition 1 relay control circuit
Did you find and correct the condition?		 - Go to Step 11  Go to Step 10 
8  Test the following circuits for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
  • The 5-volt reference circuit
  • The boost sensor signal circuit
  • The BARO sensor signal circuit
  • The A/C refrigerant pressure sensor signal circuit
  • The EGR vacuum sensor signal circuit, if applicable
  • The APP sensor signal circuit

Did you find and correct the condition?		 - Go to Step 11  Go to Step 10 
9 Replace the BARO sensor. Refer to Barometric Pressure (BARO) Sensor Replacement .
Did you complete the replacement?		 - Go to Step 11  -
10 Replace the ECM. Refer to Engine Control Module (ECM) Replacement .
Did you complete the replacement?		 - Go to Step 11  -
11
  1. Use a scan tool to clear the DTCs.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.
Does the DTC run and pass?		 - Go to Step 12  Go to Step 2 
12 With a scan tool, observe the stored information, Capture Info.
Does the scan tool display any DTCs that you have not diagnosed?		 - Go to Diagnostic Trouble Code (DTC) List System OK
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