Diagnostic Aids

WARNING: This page is about a different car, the 2004 Pontiac Grand Prix. However, it is still accessible from the selected car via links, so may be relevant.

If any sensor using a 5-volt bias voltage, such as the intake air temperature (IAT) sensor or fuel level sensor, is shorted to voltage, DTC P0641 may set in addition to DTC P0651.
For an intermittent condition, refer to Intermittent Conditions .

DTC P0651 (With Supercharger)

Step	Action	Values	Yes	No
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Controls Connector End Views or Powertrain Control Module (PCM) 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	Observe the Freeze Frame/Failure Records for this DTC. Turn OFF the ignition for 30 seconds. Start the engine. 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 cycle?	-	Go to Step 3	Go to Diagnostic Aids
3	Turn OFF the ignition. Disconnect the air conditioning (A/C) pressure sensor. Turn ON the ignition, with the engine OFF. Measure the voltage from the 5-volt reference circuit of the A/C pressure sensor to a good ground with a DMM. Refer to Circuit Testing in Wiring Systems. Is the voltage within the specified range?	4.8-5.2 V	Go to Step 4	Go to Step 5
4	Connect the A/C pressure sensor. Disconnect the barometric pressure (BARO) sensor. Measure the voltage from the 5-volt reference circuit of the BARO sensor to a good ground with a DMM. Refer to Circuit Testing in Wiring Systems. Is the voltage within the specified range?	4.8-5.2 V	Go to Intermittent Conditions	Go to Step 11
5	Is the voltage measured in the previous step more than the specified value?	5.2 V	Go to Step 8	Go to Step 6
6	Monitor the DMM while disconnecting all other devices connected to the 5-volt reference circuit, one at a time. Refer to Engine Controls Component Views . If the voltage changes when one of the devices are disconnected, replace the component. Refer to the appropriate replacement: The BARO sensor-Refer to Barometric Pressure (BARO) Sensor Replacement . The fuel level sensor-Refer to Fuel Level Sensor Replacement . Was a component replaced?	4.8-5.2 V	Go to Step 13	Go to Step 7
7	Turn OFF the ignition. Test this 5-volt reference circuit for a short to ground or any sensor low reference circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?	-	Go to Step 13	Go to Step 12
8	Monitor the DMM while disconnecting the BARO sensor. Does the voltage return to within the specified range when the BARO sensor is disconnected?	4.8-5.2 V	Go to Step 9	Go to Step 10
9	Test the BARO sensor signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?	-	Go to Step 13	Go to Step 10
10	Test all 5-volt reference circuits for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?	-	Go to Step 13	Go to Step 12
11	Replace the A/C pressure sensor. Refer to Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement in Heating, Ventilation, and Air Conditioning. Did you complete the replacement?	-	Go to Step 13	-
12	Replace the PCM. Refer to Powertrain Control Module (PCM) Replacement . Did you complete the replacement?	-	Go to Step 13	-
13	Clear the DTCs with a scan tool. Turn OFF the ignition for 30 seconds. Start the engine. 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 14
14	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