P1031

Refer to Engine Controls Schematics HO2S.

Diagnostic Chart:

CIRCUIT DESCRIPTION
The oxygen sensor heater is a device used to reduce the time that the sensor takes to go active. The PCM controls the fuel control oxygen sensor heaters using three separate drivers. With the engine running, the PCM turns ON the heaters using a high side, and a low side driver. This helps warm-up the oxygen sensors. The PCM uses a third driver to test the oxygen sensor heaters. This driver contains current monitoring circuitry, when used in a diagnostic sequence with the other drivers, indicates. the condition of the heaters. The PCM monitors this driver for circuit conditions that are incorrect for the commanded state of the driver. If the PCM detects an incorrect circuit condition, DTC P1031 will set.

CONDITIONS FOR RUNNING THE DTC
System voltage is between 9 and 18 volts.

CONDITIONS FOR SETTING THE DTC
The PCM detects an incorrect circuit condition for the commanded state of the current monitor driver.

ACTION TAKEN WHEN THE DTC SETS
^ The PCM will illuminate the Malfunction Indicator Lamp (MIL) during the second consecutive trip in which the diagnostic has been run and failed.
^ The PCM will store conditions which were present when the DTC set as Freeze Frame and Fail Records.

CONDITIONS FOR CLEARING THE MIL/DTC
^ The PCM will turn the MIL OFF 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 Clear DTC Information function.

DIAGNOSTIC AIDS
If the condition is intermittent, refer to Intermittent Conditions. Intermittent Conditions