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Diagnostic Aids

WARNING: This page is about a different car, the 2004 Pontiac Aztek and 2004 Buick Rendezvous. However, it is still accessible from the selected car via links, so may be relevant.
DTC P0641

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
  1. Observe the Freeze Frame/Failure Records 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.
Did the DTC fail this ignition?		 - Go to Step 3  Go to Intermittent Conditions
3
  1. Turn OFF the ignition.
  2. Disconnect the exhaust gas recirculation (EGR) valve.
  3. Turn ON the ignition, with the engine OFF.
  4. Command the EGR solenoid to 100 percent with a scan tool.
  5. Measure the voltage from the 5-volt reference circuit 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 5  Go to Step 4 
4 Is the voltage measured in the previous step more than the specified value? 5.2 V Go to Step 8  Go to Step 6 
5
  1. Connect the EGR valve.
  2. Disconnect the manifold absolute pressure (MAP) sensor.
  3. Command the EGR solenoid to 100 percent with a scan tool.
  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 in Wiring Systems.
Is the voltage within the specified range?		 4.8-5.2 V Go to Diagnostic Aids Go to Step 11 
6
  1. Monitor a 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 13  Go to Step 7 
7
  1. Turn OFF the ignition.
  2. Disconnect the powertrain control module (PCM).
  3. Test the 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
  1. Monitor the DMM while disconnecting the MAP sensor and fuel tank pressure (FTP) sensor, one at a time. Refer to Engine Controls Component Views .
  2. If the voltage returns to within the specified value when one of the devices is disconnected, test that sensors signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 4.8-5.2 V Go to Step 13  Go to Step 9 
9 Test the 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 10 
10 Test for a short between the EGR 5-volt reference circuit and the EGR solenoid high control 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 
11 Replace the EGR valve. Refer to Exhaust Gas Recirculation (EGR) Valve Replacement .
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
  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 System OK
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