P0108
DTC P0108 MAP Sensor Circuit High Voltage
Circuit Description
The Manifold Absolute Pressure (MAP) sensor is mounted in the intake manifold. The MAP sensor measures pressure changes within the intake manifold which is an indication of engine load. The MAP sensor has a 5.0 volt reference, a ground, and a signal circuit. When the manifold pressure is low (high vacuum) the sensor output voltage is low. When the manifold pressure is high (low vacuum) the sensor output voltage is high.
The MAP sensor voltage (depending on altitude) can range from 1.0 - 1.5 volts at idle (high vacuum) to 4.0 - 4.9 volts at wide open throttle (low vacuum).
This DTC is designed to detect MAP sensor signal voltages higher than possible in a normally operating MAP sensor.
Conditions for Running the DTC
- No active TP sensor DTCs
- The engine is running
- The throttle position is less than 0.4% when engine speed is less than 1200 RPM
OR
The throttle position is less than 20% when engine speed is greater than 1200 RPM
- The MAP is greater than or equal to 4.9 The DTC
Conditions for Setting the DTC
The MAP voltage is greater than 4.4 The DTC for more than 1 second.
Action Taken When the DTC Sets
- The VCM illuminates the MIL (Malfunction Indicator Lamp) if a failure is detected during 2 consecutive key cycles.
- The VCM will set the DTC and records the operating conditions at the time the diagnostic fails. The VCM stores the failure information in the scan tools Freeze Frame and/or the Failure Records.
Conditions for Clearing the MIL/DTC
- The VCM turns OFF the MIL after 3 consecutive drive trips when the test has Run and Passed.
- A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles (coolant temperature has risen 22 °C (40 °F) from the startup coolant temperature and the engine coolant temperature is more than 70 °C (158 °F) during the same ignition cycle).
- Use the scan tool Clear Information function.
Diagnostic Aids
An intermittent ground in the MAP signal or the 5 volts reference circuit could result in other DTC's Also an open or short to voltage or ground in the 5 volt reference could result in a DTC.
With the ignition ON and the engine OFF, the manifold pressure is equal to atmospheric pressure with the signal voltage high. The VCM uses this information as an indication of the vehicle's altitude. Comparison of this reading with a known good vehicle using the same sensor is a good way to check accuracy of a suspect sensor. Readings should be within 0.4 volts. Refer to Symptoms.
IMPORTANT: After removing the MAP sensor from the intake manifold, replace the MAP sensor to intake manifold seal
Remove the MAP sensor. Twist sensor by hand (only) to check for intermittent connections. Output changes greater than 0.1 volt indicates a bad connector or connection. If OK, replace sensor.
An intermittent may be caused by any of the following conditions:
- A poor connection
- Rubbed through wire insulation
- A broken wire inside the insulation
Thoroughly check any circuitry that is suspected of causing the intermittent complaint. Refer to Intermittents and Poor Connections Diagnosis.
If a repair is necessary, then refer to Wiring Repairs or Connector Repairs.
Steps 1 - 5:
Steps 6 - 10:
Steps 11 - 16:
Steps 17 - 18:
Test Description
The numbers below refer to the step numbers on the diagnostic table.
IMPORTANT: Be sure to use the same diagnostic equipment for all measurements.
5. This step checks for a short to voltage on the 5 volt reference circuit.
7. This step checks the integrity of the MAP sensor ground circuit.
10. The VCM terminals C3 12 and C3 27 are spliced together inside the VCM. When checking the 5 volt reference for a short to ground, both the 5 volt reference circuits and all of the components on the 5 volt reference circuits must also be checked.