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Test Description

WARNING: This page is about a different car, the 2006 Chevrolet Monte Carlo and 2006 Chevrolet Impala. 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. 9:  A short to voltage on the signal circuit of the FTP sensor will backfeed through the sensor into the 5-volt reference circuit and set this DTC.
DTC P0641

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
  1. Observe the Freeze Frame and/or Failure Records for the 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 Testing for Intermittent Conditions and Poor Connections
3
  1. Turn OFF the ignition.
  2. Disconnect the manifold absolute pressure (MAP) sensor electrical connector.
  3. Turn ON the ignition, with the engine OFF.
  4. Measure the voltage from the 5-volt reference circuit of the MAP sensor to a good ground with a DMM. Refer to Circuit Testing .
Is the voltage within the specified range?		 4.8-5.2 V Go to Step 5  Go to Step 4 
4 Is the voltage from the previous step more than the specified value? 5.2 V Go to Step 8  Go to Step 6 
5
  1. Connect the MAP sensor.
  2. Disconnect the air conditioning (A/C) refrigerant pressure sensor.
  3. Measure the voltage from the 5-volt reference circuit of the A/C refrigerant pressure sensor to a good ground with a DMM. Refer to Circuit Testing .
Is the voltage within the specified range?		 4.8-5.2 V Go to Testing for Intermittent Conditions and Poor Connections Go to Step 10 
6
  1. Monitor the DMM while disconnecting all other sensors connected to this 5-volt reference bus, one at a time.
  2. If the voltage changes when one of the above components is disconnected, replace the component. Refer to the appropriate replacement procedure.
Was a component replaced?		 - Go to Step 13  Go to Step 7 
7 Test the 5-volt reference circuits of all of the sensors connected to this 5-volt reference bus for a short to ground or any sensor low reference circuit. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?		 - Go to Step 13  Go to Step 12 
8
IMPORTANT: If a short to voltage occurs, the A/C refrigerant pressure sensor may be damaged.
Test the 5-volt reference circuits of all the sensors connected to this 5-volt reference bus for a short to voltage. Refer to Circuit Testing and Wiring Repairs .Did you find and correct the condition?		 - Go to Step 13  Go to Step 9 
9 
IMPORTANT: If a short to voltage occurs on the fuel tank pressure (FTP) sensor signal circuit, the FTP sensor may be damaged.
Test the FTP sensor signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs .Did you find and correct the condition?		 - Go to Step 13  Go to Step 12 
10
IMPORTANT: If a short to voltage occurs on the MAP sensor signal circuit, the MAP sensor may be damaged.
Test the MAP sensor signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs .Did you find and correct the condition?		 - Go to Step 13  Go to Step 11 
11 Replace the MAP sensor. Refer to Manifold Absolute Pressure (MAP) Sensor Replacement .
Did you complete the replacement?		 - Go to Step 13  -
12 Replace the engine control module (ECM). Refer to Control Module References for replacement, setup, and programming.
Did you complete the replacement?		 - Go to Step 13  -
13
  1. Clear the DTCs with a 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 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 - Vehicle System OK
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