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 2.0 volts at idle (high vacuum) to above 4.0 volts with the key on, engine not running, or engine running at wide open throttle (low vacuum).
The MAP sensor is used to determine manifold pressure changes while the linear EGR flow test diagnostic is being run (refer to DTC P0401 Exhaust Gas Recirculation (EGR) Flow Insufficient ), to determine engine vacuum level for other diagnostics and to determine barometric pressure (BARO). 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 be set.
Conditions for Running the DTC
| • | No active TP sensor DTC present. |
| • | Engine running for a length of time determined by start up coolant temperature. The length of time ranges from 2 minutes at less than -30°C (-22°F) to 0.5 seconds at more than 30°C (86°F). |
| • | System voltage greater than 9.0 volts. |
| • | Throttle position below 30 percent if engine speed is above 3000 rpm. |
| • | Throttle position below 2 percent if engine speed is below 3000 rpm. |
Conditions for Setting the DTC
| • | The MAP sensor signal is greater than 4.3 volts. |
| • | The above conditions greater than 2 seconds. |
Action Taken When the DTC Sets
| • | The PCM illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. |
| • | The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the PCM stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the PCM records the operating conditions at the time of the failure. |
| • | The PCM writes the conditions to the Freeze Frame and updates the Failure Records. |
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:
| • | Monitor the MAP sensor using the scan tool. If the MAP sensor does not respond to throttle changes, check the 3X reference circuits from the ignition control module to the PCM. |
| • | If the 3X reference signal is lost the PCM will only update the MAP sensor reading once per key cycle, when the engine is first started. |
| • | Depending on where the MAP sensor voltage (high voltage or low voltage) is when the engine is started, the high or low voltage MAP sensor DTCs will set. |
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.
| • | Poor terminal connection. |
| Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and faulty terminal to wire connection. Use a corresponding mating terminal to test for proper tension. Refer to Intermittents and Poor Connections Diagnosis , and Connector Repairs Wiring Systems. |
| • | Damaged harness. |
| Inspect the wiring harness for damage. If the harness appears to be OK, observe the sensor display on the scan tool while moving connectors and wiring harnesses related to the sensor. A change in the sensor display may indicate the location of the fault. Refer to Wiring Repairs in Wiring Systems. |
| • | Inspect the PCM and the engine grounds for clean and secure connections. |
If the DTC is determined to be intermittent, reviewing the Fail Records can be useful in determining when the DTC was last set.
Test Description
The number below refers to the step numbers on the Diagnostic Table:
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the Powertrain OBD System Check performed? | -- | ||
2 |
Is the MAP voltage above the specified value? | 3.5V | ||
3 |
Does scan tool indicate DTC P0108 failed? | -- | Go to Diagnostic Aids | |
4 |
Is the MAP sensor voltage near the specified value? | 0.0V | ||
5 | Probe the MAP Sensor ground circuit with a J 35616-200 test light to battery positive voltage. Is the J 35616-200 test light on? | -- | ||
6 |
Was the MAP sensor signal circuit shorted? | -- | ||
7 |
Was a problem found? | -- | ||
8 | Test for a plugged or leaking vacuum supply to the MAP sensor. Refer to Visual/Physical Inspection in Symptoms . Is the vacuum supply OK? | -- | ||
9 |
Did the terminal require replacement? | -- | ||
10 |
Was a condition found and corrected? | -- | ||
|
Important: : Replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Is the action complete? | -- | -- | ||
12 |
Was the 5 volt reference A circuit shorted? | -- | ||
13 | Test for poor electrical connections at the MAP sensor and replace terminals if necessary. Refer to Testing for Continuity , Intermittents and Poor Connections Diagnosis , Repairing Connector Terminals , and Connector Repairs . Did any terminals require replacement? | -- | ||
14 | Replace the MAP sensor. Refer to Manifold Absolute Pressure Sensor Replacement . Is the action complete? | -- | -- | |
15 | Repair the faulty vacuum source. Is the action complete? | -- | -- | |
16 |
Does scan tool indicate DTC P0108 failed? | -- | System OK |
