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Test Description

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.

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

  1. 5:  The MAP sensor, the exhaust gas recirculation (EGR) valve, and the fuel tank pressure (FTP) sensor utilize the 5-volt reference A circuit for supply voltage. DTC P0641 sets if a failure occurs causing this system voltage to be pulled high or low. This DTC should be diagnosed first.
  2. 9:  A short to voltage on the MAP sensor signal circuit may backfeed through the sensor affecting the 5-volt reference system voltage. This step tests for this condition.
DTC P0108

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. Start the engine.
  2. Observe the manifold absolute pressure (MAP) sensor parameter with the scan tool.
Is the voltage more than the specified value?		 4.3 V Go to Step 4  Go to Step 3 
3
  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 4  Go to Intermittent Conditions
4 Inspect the MAP sensor vacuum source for the following conditions:
  • Leaks
  • Restrictions
  • Faulty Connections

Did you find and correct the condition?		 - Go to Step 15  Go to Step 5 
5  Monitor the DTC information with the scan tool.
Is DTC P0641 also set?		 - Go to Step 9  Go to Step 6 
6 Test for an intermittent and for a poor connection at the MAP sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 15  Go to Step 7 
7
  1. Disconnect the MAP sensor electrical connector.
  2. Turn ON the ignition, with the engine OFF.
  3. Observe the MAP sensor parameter with the scan tool.
Is the voltage less than the specified value?		 0.1 V Go to Step 8  Go to Step 10 
8
  1. Connect a jumper wire between each of the terminals in the MAP sensor harness connector and the corresponding terminal at the MAP sensor. Refer to Using Connector Test Adapters in Wiring Systems.
  2. Measure the voltage from the low reference circuit of the MAP sensor at the jumper wire terminal to a good ground with a DMM. Refer to Measuring Voltage Drop in Wiring Systems.
Is the voltage more than the specified value?		 0.2 V Go to Step 11  Go to Step 13 
9 
  1. Turn OFF the ignition.
  2. Disconnect the MAP sensor electrical connector.
  3. Turn ON the ignition, with the engine OFF.
  4. Observe the MAP sensor parameter with the scan tool.
Is the voltage less than the specified value?		 0.1 V Go to DTC P0641 Go to Step 10 
10
IMPORTANT: Disconnecting the powertrain control module (PCM) may eliminate the short during testing.
IMPORTANT: The MAP sensor may have been damaged if the circuit was shorted to a voltage source.
Test the MAP sensor signal circuit between the PCM and the MAP sensor 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 15  Go to Step 14 
11 Test the low reference circuit between the PCM and the MAP sensor for high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 15  Go to Step 12 
12 Test for an intermittent and for a poor connection at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 15  Go to Step 14 
13 Replace the MAP sensor. Refer to Manifold Absolute Pressure (MAP) Sensor Replacement (L26) or Manifold Absolute Pressure (MAP) Sensor Replacement (L32) .
Did you complete the replacement?		 - Go to Step 15  -
14 Replace the PCM. Refer to Powertrain Control Module (PCM) Replacement .
Did you complete the replacement?		 - Go to Step 15  -
15
  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 form 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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