P0108 (Federal RPO NF2 or NF4)

CIRCUIT DESCRIPTION
The barometric pressure (BARO) sensor responds to changes in altitude and atmospheric conditions. This gives the engine control module (ECM) an indication of barometric pressure. The ECM uses this information to calculate fuel delivery. The BARO sensor has a 5-volt reference circuit, a low reference circuit, and a signal circuit. The ECM supplies 5 volts to the BARO sensor on the 5-volt reference 2 circuit, and provides a ground on a low reference circuit. The BARO sensor provides a signal to the ECM on a signal circuit relative to the pressure changes. The ECM monitors the BARO sensor signal for voltage outside of the normal range. If the ECM detects a BARO sensor signal voltage that is excessively high, this DTC will set.

CONDITIONS FOR RUNNING THE DTC
The ignition is ON.

CONDITIONS FOR SETTING THE DTC
The BARO is more than 110 kPa for 2 seconds.

ACTION TAKEN WHEN THE DTC SETS
^ The control module stores the DTC information into memory when the diagnostic runs and fails.
^ The malfunction indicator lamp (MIL) will not illuminate.
^ The control module records the operating conditions at the time the diagnostic fails. the control module stores this information in the Failure Records.
^ The driver information center, if equipped, may display a message.

CONDITIONS FOR CLEARING THE DTC
^ A current DTC Last Test Failed clears when the diagnostic runs and passes.
^ A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
^ Use a scan tool in order to clear the DTC.

TEST DESCRIPTION

DTC P0108 (Federal RPO NF2 Or NF4) - Steps 1-10:

DTC P0108 (Federal RPO NF2 Or NF4) - Steps 11-18:

The numbers below refer to the step numbers on the diagnostic table.
4. A short to voltage on the 5-volt reference circuit will cause DTC P1639 to set.
7. This step tests the signal circuit of the BARO sensor for a short to voltage. The short may backfeed through the sensor to the 5- volt reference circuit causing the DTC P1639 to set.
8. This step tests the signal circuit of the boost sensor for a short to voltage. The short may backfeed through the sensor to the 5-volt reference circuit causing the DTC P1639 to set

For a description of the RPO Code(s) shown in this article or any of the images therein, refer to the RPO Code List found at Vehicle/Application ID". RPO Codes