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 linear EGR flow test diagnostic is being run, to etermine 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. |
| • | Throttle angle above 0%, if engine speed is below 1000 RPM. |
| • | Throttle angle above 10%, if engine speed is above 1000 RPM. |
Conditions for Setting the DTC
The MAP sensor signal is greater than 91.8 kPa.
Action Taken When the DTC Sets
| • | The PCM will illuminate the malfunction indicator lamp (MIL) during the second consecuitive trip in which the diagnostic has been run and failed. |
| • | If equipped with traction control, the PCM will command the EBTCM via the serial data circuit to turn OFF traction control, and the EBTCM will illuminate the TRACTION OFF lamp. |
| • | The PCM will store conditions which were present when the DTC set as Freeze Frame and Failure Records data. |
Conditions for Clearing the MIL/DTC
| • | The PCM will turn OFF the MIL during the third consecutive trip in which the diagnostic has been 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 the 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 circuits from the ignition control module to the PCM. |
| If the 3X 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. |
| • | Poor connection at PCM. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and 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 fault. |
If DTC P0108 cannot be duplicated, the information included in the Fail Records data can be useful in determining since the DTC was last set. If it is determined that the DTC occurs intermittently, performing the DTC P1108 Diagnostic Chart may isolate the cause of the fault.
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 at the specified value? | 0.0V | ||
5 | Probe the 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 | Check for a plugged or leaking vacuum supply to the MAP sensor. Is the vacuum supply OK? | -- | ||
9 |
Did the terminal require replacement? | -- | ||
10 |
Was a condition found and corrected? | -- | ||
Replace the PCM. Important: : Replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Is the action complete? | -- | -- | ||
12 |
Was the 5 volt reference A circuit shorted? | -- | ||
13 | Check for poor electrical connections at the MAP sensor and replace terminals if necessary. disconnect the PCM. 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 |
