GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2005 🢒 Rendezvous - FWD 🢒 Accessories 🢒 Navigation Systems 🢒 DTC P0108

Circuit Description

The manifold absolute pressure (MAP) sensor responds to pressure changes in the intake manifold. The pressure changes occur based on the engine load. The MAP sensor has the following circuits:

    • 5-volt reference circuit
    • Low reference circuit
    • MAP sensor signal circuit

The powertrain control module (PCM) supplies 5 volts to the MAP sensor on the 5-volt reference circuit. The PCM also provides a ground on the low reference circuit. The MAP sensor provides a signal to the PCM on the MAP sensor signal circuit which is relative to the pressure changes in the manifold. The PCM should detect a low signal voltage at a low MAP, such as during an idle or a deceleration. The PCM should detect a high signal voltage at a high MAP, such as the ignition is ON, with the engine OFF, or at a wide open throttle (WOT). The MAP sensor is also used in order to determine the barometric pressure (BARO). This occurs when the ignition switch is turned ON, with the engine OFF. The BARO reading may also be updated whenever the engine is operated at WOT. The PCM monitors the MAP sensor signal for voltage outside of the normal range.

If the PCM detects a MAP sensor signal voltage that is excessively high, DTC P0108 sets.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0108 Manifold Absolute Pressure (MAP) Sensor Circuit High Voltage

Conditions for Running the DTC
    • DTCs P0121, P0122, P0123 are not set.
    • The engine has been running for a length of time that is determined by the startup coolant temperature. The length of time ranges from 2 minutes at less than -30°C (-22°F) to 1 second at more than 30°C (86°F).
    • The throttle angle is less than 2 percent when the engine speed is less than 3,000 RPM.
        OR
    • The throttle angle is less than 30 percent when the engine speed is more than 3,000 RPM.

Conditions for Setting the DTC
    • The PCM detects that the MAP sensor voltage is more than 4.3 volts for 3 seconds.
    • This diagnostic runs continuously.

Action Taken When the DTC Sets
    • The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
    • The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

Conditions for Clearing the MIL/DTC
    • The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
    • A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
    • A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
    • Clear the MIL and the DTC with a scan tool.

Diagnostic Aids

This DTC may set due to poor idle characteristics. A possible cause may be uncontrolled fueling due to an open or high resistance in the HO2S 1 low signal circuit. Before replacing any component, ensure that this condition does not exist.

Test Description

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

  1. This step tests for improper throttle position (TP) sensor operation.

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics

Connector End View Reference: Engine Controls Connector End Views or Powertrain Control Module Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. Turn ON the ignition, with the engine OFF.
  2. Monitor the DTC information with the scan tool.

Is DTC P0641 also set?

--

Go to Diagnostic Trouble Code (DTC) List - Vehicle

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:
    3. • MAP sensor disconnected from the vacuum source
    • Vacuum line damaged
    • Blocked port

Did you find and correct the condition?

--

Go to Step 17

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 17

Go to Step 8

8
  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 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 .
  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 .

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.
   • 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 .

Did you find and correct the condition?

--

Go to Step 17

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 .

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 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 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 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