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Home >> Buick >> 2007 >> Lucerne CX >> Repair and Diagnosis >> External Pages >> Different car >> Section 64 (Engine Control System - 3.8L (DTC P0016 To DTC P0138)) >> Diagnosis >> DTC P0108 >> Diagnostic Aids

Diagnostic Aids

WARNING: This page is about a different car, the 2005 Buick LaCrosse and 2005 Buick Allure. However, it is still accessible from the selected car via links, so may be relevant.

This DTC may set due to poor idle characteristics as a result of uncontrolled fueling caused by an open or high resistance in the HO2S 1 low signal circuit. Before replacing any component ensure that this condition does not exist.

DTC P0108

Step Action Values Yes No
Schematic Reference: Engine Controls Schematics
Connector End View Reference: Powertrain Control Module (PCM) 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. Start the engine.
  2. Observe the 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 manifold absolute pressure (MAP) sensor vacuum source for the following conditions:
  • A leak
  • A restriction
  • A faulty connection

Did you find and correct the condition?		 - Go to Step 17  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 .
Did you find and correct the condition?		 - Go to Step 17  Go to Step 7 
7
  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 Step 8  Go to Step 10 
8
  1. Turn OFF the ignition.
  2. 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 .
  3. Turn ON the ignition, with the engine OFF.
  4. Measure the voltage from the low reference circuit of the MAP sensor at the jumper wire terminal to a good ground with the DMM. Refer to Measuring Voltage Drop .
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 Test the MAP sensor signal circuit between the powertrain control module (PCM) and the MAP sensor for a short to voltage. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?		 - Go to Step 17  Go to Step 15 
11 Test the low reference circuit between the PCM and the MAP sensor for an open or for high resistance. Refer to Circuit Testing andWiring Repairs .
Did you find and correct the condition?		 - Go to Step 17  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 .
Did you find and correct the condition?		 - Go to Step 17  Go to Step 16 
13 Test the HO2S 1 low signal circuit for an open or for high resistance. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?		 - Go to Step 17  Go to Step 15 
14 Test the HO2S 1 low signal circuit for an open or for high resistance. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?		 - Go to Step 17  Go to Step 16 
15 Replace the MAP sensor. Refer to Manifold Absolute Pressure (MAP) Sensor Replacement .
Did you complete the replacement?		 - Go to Step 17  -
16 Replace the PCM. Refer to Control Module References for replacement, setup, and programming.
Did you complete the replacement?		 - Go to Step 17  -
17
  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 18 
18 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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