GM Service Manual Online
For 1990-2009 cars only

Object Number: 516716  Size: SF
Engine Controls Components
A/C Pressure Sensor, TP, MAP, ECT and IAT
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice

Circuit Description

The manifold absolute pressure (MAP) sensor responds to changes in intake manifold pressure (vacuum). The MAP sensor signal voltage to the Powertrain Control Module (PCM) varies from below 2 volts at idle (high vacuum) to above 4 volts with the key ON, engine not running or at wide open throttle (low vacuum). The MAP sensor is used to determine manifold pressure changes while the exhaust gas recirculation (EGR) flow test diagnostic is being run, refer to DTC P0401 Exhaust Gas Recirculation (EGR) Flow Insufficient . Also to update the barometric pressure reading (BARO), as an enabling factor for other diagnostics. The PCM monitors the MAP signals for voltages outside the normal range of the MAP sensor. If the PCM detects a MAP signal voltage that is excessively high, DTC P0108 will set.

Conditions for Running the DTC

    • No TP sensor DTCs present
    • System voltage is more than 9 volts
    • 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).
    • Throttle angle below 2 percent, if engine speed is less than 900 RPM.
    • Throttle angle below 30 percent, if engine speed is more than 3000 RPM.

Conditions for Setting the DTC

The MAP sensor signal voltage is more than 91.8 kPa or 4.3 volts.

Action Taken When the DTC Sets

    • The PCM will illuminate the malfunction indicator lamp (MIL) during the second consecutive trip in which the diagnostic test has been run and failed.
    • The PCM will store conditions which were present when the DTC set as Freeze Frame/Failure Records data.

Conditions for Clearing the MIL/DTC

    • The PCM will turn OFF the malfunction indicator lamp (MIL) during the third consecutive trip in which the diagnostic has run and passed.
    • The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.
    • The DTC can be cleared by using a scan tool.

Diagnostic Aids

Inspect for the following conditions:

    • Poor connection at the PCM--Inspect harness connectors for:
      • Backed out terminals
      • Improper mating
      • Broken locks
      • Improperly formed or damaged terminals
      • Poor terminal to wire connection
    • Damaged harness--Inspect the wiring harness for damage. If the harness appears to be OK, observe the MAP display on the scan tool while moving connectors and wiring harnesses related to the sensor. A change in the display will indicate the location of the malfunction.

If the DTC cannot be duplicated and is determined to be intermittent, reviewing the Failure Records can be useful in determining when the DTC was last set. Also refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Test Description

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

  1. This vehicle is equipped with a PCM which utilizes an electrically erasable programmable read only memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed.

DTC P0108 - MAP Sensor Circuit High Voltage

Step

Action

Values

Yes

No

1

Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2

  1. If the engine idle is rough, unstable or incorrect, repair the idle problem before continuing with this table. Refer to Rough, Unstable, or Incorrect Idle and Stalling in Symptoms.
  2. With the engine idling, observe the MAP voltage parameter on a scan tool.

Does the scan tool indicate that the MAP voltage parameter is more than the specified value?

4.2 V

Go to Step 4

Go to Step 3

3

  1. Turn ON the ignition, with the engine OFF.
  2. Review and record the scan tool Failure Records data.
  3. Operate the vehicle within the Failure Records conditions.
  4. Using a scan tool, monitor Specific DTC info for DTC P0108.

Does the scan tool indicate DTC P0108 failed?

--

Go to Step 4

Go to Diagnostic Aids

4

  1. Turn OFF the ignition.
  2. Disconnect the MAP sensor.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool, observe the MAP voltage parameter.

Does the scan tool indicate that the MAP voltage parameter is at the specified value?

0 V

Go to Step 5

Go to Step 7

5

Test for a plugged or leaking vacuum supply to the MAP sensor.

Did you find and correct the condition?

 

Go to Step 12

Go to Step 6

6

Test the ground circuit of the MAP sensor for continuity. Refer to Testing for Continuity in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 8

7

Test the signal circuit of the MAP sensor for a short to voltage or short to 5 volt reference A circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 11

8

Inspect the ground circuit of the MAP sensor at the PCM for a poor connection at the harness connector. 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 12

Go to Step 9

9

Inspect the ground circuit of the MAP sensor at the MAP sensor for poor connections at the harness connector. 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 12

Go to Step 10

10

Replace the MAP sensor. Refer to Manifold Absolute Pressure Sensor Replacement .

Did you complete the replacement?

--

Go to Step 12

--

11

Important:: The replacement PCM must be programmed.

Replace the PCM. Refer to Powertrain Control Module Replacement/Programming .

Did you complete the replacement?

--

Go to Step 12

--

12

  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

--

Go to Step 4

System OK