Circuit Description
The manifold absolute pressure (MAP) sensor responds to changes in intake manifold pressure. The MAP sensor signal voltage to the powertrain control module (PCM) varies from less than 2 volts at idle, or high vacuum, to more than 4 volts with the key ON, and the engine is not running or at Wide-Open Throttle, low vacuum. The MAP sensor is used to determine manifold pressure changes while the EGR flow test diagnostic is being run, and also to update the barometric pressure reading (BARO), as an enabling factor for other diagnostics. Refer to DTC P0401 Exhaust Gas Recirculation (EGR) Flow Insufficient . 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 throttle position (TP) sensor DTCs are present. |
| • | The system voltage is more than 9.0 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). |
| • | The throttle position is below 2 percent, if the engine speed is less than 3000 RPM. |
| • | The throttle position is below 30 percent if engine speed is above 3000 RPM. |
Conditions for Setting the DTC
| • | The MAP sensor signal voltage is more than 4.3 volts. |
| • | The above conditions are present for longer than 200 3X reference periods, 67 crankshaft revolutions. |
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 a misrouted harness-- Inspect the MAF sensor harness to ensure that it is not routed too close to high voltage wires such as spark plug leads.
Many situations may lead to an intermittent condition. Perform each inspection or test as directed.
Important: : Remove any debris from the connector surfaces before servicing a component. Inspect the connector gaskets when diagnosing or replacing a component. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion.
| • | Loose terminal connection |
| - | Use a corresponding mating terminal to test for proper tension. Refer to Testing for Intermittent Conditions and Poor Connections , and to Connector Repairs in Wiring Systems for diagnosis and repair. |
| - | Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and faulty terminal to wire connection. Refer to Testing for Intermittent Conditions and Poor Connections , and to Connector Repairs in Wiring Systems for diagnosis and repair. |
| • | Damaged harness--Inspect the wiring harness for damage. If the harness inspection does not reveal a problem, observe the display on the scan tool while moving connectors and wiring harnesses related to the sensor. A change in the scan tool display may indicate the location of the fault. Refer to Wiring Repairs in Wiring Systems for diagnosis and repair. |
| • | Inspect the powertrain control module (PCM) and the engine grounds for clean and secure connections. Refer to Wiring Repairs in Wiring Systems for diagnosis and repair. |
If the condition is determined to be intermittent, reviewing the Snapshot or Freeze Frame/Failure Records may be useful in determining when the DTC or condition was identified.
Test Description
The numbers below refer to the step numbers on the Diagnostic Table:
Step | Action | Values | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On Board Diagnostic (OBD) System Check? | -- | ||
2 |
Does the scan tool indicate that the MAP voltage parameter is more than the specified value? | 4.3 V | ||
3 |
Does the scan tool indicate DTC P0108 failed? | -- | Go to Diagnostic Aids | |
4 |
Does the scan tool indicate that the MAP voltage parameter is at the specified value? | 0.0 V | ||
5 | Test for a plugged or leaking vacuum supply to the MAP sensor. Did you find and correct the condition? | |||
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? | -- | ||
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? | -- | ||
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? | -- | ||
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? | -- | ||
10 | Replace the MAP sensor. Refer to Manifold Absolute Pressure Sensor Replacement . Did you complete the replacement? | -- | -- | |
|
Important: The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Did you complete the replacement? | -- | -- | ||
12 |
Does the DTC reset? | -- | System OK |
