P0108

Manifold Absolute Pressure (MAP) Sensor Circuit:

Circuit Description
The PCM uses the Manifold Absolute Pressure (MAP) sensor output voltage to assist in controlling fuel delivery and ignition timing. The PCM supplies a 5 volt reference signal voltage and a ground to the MAP sensor. As the manifold pressure changes, the output voltage of the sensor also changes. By monitoring the sensor output voltage, the PCM knows the manifold pressure. A lower pressure (low voltage) output voltage will be about 1.0 to 1.5 volts at idle. While higher pressure (high voltage) output voltage will be about 4.5 to 4.8 volts at Wide Open Throttle (WOT). The MAP sensor is also used to record barometric pressure during engine start up and wide at open throttle. This allows the PCM to make adjustments for different altitudes.

Conditions for Setting the DTC
- The MAP sensor is greater than 82 kPa.
- The Throttle Position (TP) sensor is less than 12%.
- The vehicle speed sensor is less than 1 mph (2 km/h).
- The above conditions met for 10 seconds.
- The engine run time is greater than 20 to 40 seconds.
- DTCs P0122 or P0123 not set.

Action Taken When the DTC Sets
- The Malfunction Indicator Lamp (MIL) will illuminate.
- The PCM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records buffers.
- A history DTC is stored.
- The PCM will substitute a fixed MAP value and use throttle position to control three fuel delivery. The scan tool will not show the defaulted value.

Conditions for Clearing the MIL/DTC
- The MIL will turn "OFF" after three consecutive ignition cycles in which the diagnostic runs without a fault.
- A history DTC will clear after 40 consecutive warm up cycles without a fault.
- DTCs can be cleared by using a scan tool.

Diagnostic Aids
With the ignition "ON" and the engine "OFF," the manifold pressure is equal to atmospheric pressure and the signal voltage will be high. This information is used by the PCM as an indication of vehicle altitude. Comparison of this reading with a known good vehicle with the same sensor is a good way to check the accuracy of a "suspect' sensor. Readings should be the same ±0.4 volt.
Whenever a DTC P0108 is intermittent, refer to Manifold Absolute Pressure Output Check for further diagnosis.

NOTE:
- After repairs use scan tool Fuel Trim Reset function to reset long term fuel trim to 128 (0%).
- Whenever misfire is present, repair the cause of misfire before using this table. The misfire counters may be used to determine which cylinder(s) is misfiring.

DTC P0108 - Manifold Absolute Pressure (MAP) Sensor Circuit High Voltage (1 Of 2):

DTC P0108 - Manifold Absolute Pressure (MAP) Sensor Circuit High Voltage (2 Of 2):

Test Description
Numbers below refer to the step numbers on the Diagnostic Table.
1. The OBD System Check prompts the Technician to complete some basic checks and store the Freeze Frame Data and the Failure records on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. This information on the scan tool can be referred to later.
2. This will determine if DTC P0108 is the result of a hard fault or an intermittent condition.
3. Whenever the PCM recognizes the change, the PCM, the MAP sensor 5V reference circuit and the MAP sensor signal circuit are OK.
5. Whenever the circuit is open, additional DTCs may also set. When no other DTCs are set and the circuit is found to be open, then the open must be between the MAP sensor and the electrical connector.
6. When the MAP sensor signal circuit is shorted to battery voltage, the TP sensor will be displayed above 0% at all times and the A/C High side will be displayed high. The vehicle will also remain in Open Loop.
11. Before replacing the PCM, check terminals for improper mating, broken locks, or physical damage to the wiring harness. Replacement PCM must be reprogrammed. Refer to the latest Techline information for programming procedures.