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Home >> Buick >> 2004 >> Century Base >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls (DTC P0030 To P0138) >> Engine Controls Diagnosis >> DTC P0108 >> Test Description
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Test Description

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

  1. 3:  This step tests for improper throttle position (TP) sensor operation.
P0108- MAP Sensor Circuit High Voltage

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. Turn ON the ignition with the engine OFF.
  2. Monitor the diagnostic trouble code (DTC) information with the scan tool.
Is DTC P0641 also set?		 - Go to DTC P0641 Go to Step 3 
3 
  1. Observe the throttle position (TP) sensor parameter with the scan tool.
  2. Press the accelerator pedal slowly until the throttle is in the wide open position.
  3. Release the accelerator pedal slowly until the throttle is returned to the closed position.
  4. Repeat this procedure several times.
Does the TP sensor parameter increase steadily to more than the first specified value, and then decrease steadily returning to less than the second specified value?		 98%
1%		 Go to Step 4  Go to DTC P0121 
4
  1. Start the engine.
  2. Observe the MAP sensor parameter with a scan tool.
Is the voltage more than the specified value?		 4.3 V Go to Step 6  Go to Step 5 
5
  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 as specified in the supporting text or as close to the Freeze Frame/Failure Records data that you observed.
Does the DTC fail this ignition?		 - Go to Step 6  Go to Intermittent Conditions
6
  1. Turn OFF the ignition.
  2. Inspect the manifold absolute pressure (MAP) sensor and the vacuum source for the following conditions:
    • MAP sensor disconnected from the vacuum source
    • Vacuum line damaged
    • Blocked port
Did you find and correct the condition?		 - Go to Step 15  Go to Step 7 
7 Test for an intermittent and for a poor connections 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 8 
8
  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 9  Go to Step 10 
9
  1. Turn OFF the ignition.
  2. Disconnect the electrical connector of the engine coolant temperature (ECT) sensor.
  3. 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.
  4. Turn ON the ignition, with the engine OFF.
  5. 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 
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 for 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 .
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 from 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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