Circuit Description
The manifold absolute pressure (MAP) sensor responds to changes in intake manifold pressure (vacuum). The MAP sensor signal voltage to the 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 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 more than 9 volts |
| • | Engine has been running for a length of time that is determined by startup coolant temperature. The length of time ranges from 2 minutes at less than -30°C (-22°F) to 0.5 second at more than 30°C (86°F). |
| • | Idle speed is steady. |
| • | Throttle position below 2 percent. |
| • | Engine speed is less than 900 RPM. |
Conditions for Setting the DTC
| • | The MAP sensor signal voltage is more than 4.2 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
Check for the following conditions:
| • | Poor connection at the PCM -- Inspect harness connectors for the following conditions: |
| - | 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:
Step | Action | Values | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||
2 |
Important: If DTC P1635 5 Volt Reference Circuit is also set, perform that diagnostic first.
Does the scan tool indicate that the MAP voltage parameter is more than the specified value? | 4.2 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 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? | -- | 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? | -- | ||
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? | -- | -- | |
11 |
Important:: Perform the set up procedure for the PCM. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Did you complete the replacement? | -- | -- | |
12 |
Does the DTC reset? | -- | System OK |
