P0108

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

Wiring Diagram:

Circuit Description
The Engine Control Module (ECM) uses the Manifold Absolute Pressure (MAP) sensor to control the fuel delivery and the ignition timing. The MAP sensor measures the changes in the intake manifold pressure, which results from engine load (intake manifold vacuum) and the RPM changes; and converts these into voltage outputs. The ECM sends a 5 volt reference voltage to the MAP sensor. As the manifold pressure changes, the output voltage of the MAP sensor also changes. By monitoring the MAP sensor output voltage, the ECM knows the manifold pressure. A low-pressure (low voltage) output voltage will be about 1.1 - 1.5 V at idle, while higher pressure (high voltage) output voltage will be about 4.5 - 5.0 V at Wide Open Throttle (WOT). The MAP sensor is metric pressure, allowing the ECM to make adjustments for different altitudes.

Conditions for Setting the DTC
- Ignition ON.
- MAP sensor voltage is higher than 4.927 V for more than 1 second.
Action Taken When the DTC Sets
- The Malfunction Indicator Lamp (MIL) will illuminate.
- The ECM 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.

Conditions for Clearing the MIL/DTC
- The MIL will turn OFF at the end of a consecutive cycle in which the diagnostic runs without a fault.
- A history DTC will clear after 40 warm up cycles without a fault.
- DTC(s) can be cleared by using the scan tool.

Diagnostic Aids
With the ignition ON and the engine stopped, the manifold pressure is equal to atmosphere pressure and the signal voltage will be high. The ECM as an indication of vehicle altitude uses this information. 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 V. If a DTC P0108 is intermittent, refer to Manifold Absolute Pressure Check for further diagnosis. Testing and Inspection

If the connections are OK monitor the Manifold Absolute Pressure (MAP) sensor signal voltage while moving related connectors and the wiring harness. If the failure is induced, the display on the scan tool will change. This may help to isolate the location of an intermittent malfunction.

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DTC Troubleshooting