P0031

Diagnostic Chart:

Schematic:

The front oxygen sensors are equipped with heaters to assist in ramping up to the nominal operating temperature of the front oxygen sensors. This decreases the amount of time required to enter closed-loop operation where maximum fuel efficiency is attained. The ECM diagnoses the heater and it's related wiring by continuously monitoring electrical current. The ECM will set this DTC when the signal being received is lower than expected.

DTC PARAMETERS
This DTC will set when:
^ Heater voltage less than 2.34 volts
^ Battery voltage is not between 11.03 and 15.52 volts
^ Above condition have been met for 50 ms

DTC P0031 is a (type B) DTC

DIAGNOSTIC AIDS
To locate an intermittent problem use the Scan tool to monitor HO2S Heater Bn 1 Sen. 1 voltage with engine idling at normal operating temperature.

Wiggling wires while monitoring HO2S Bn 1 Sen. 1 voltage may locate area where a short to ground may exist.

Review failure record information to check if the vehicle was running lean in power enrichment (TP angle greater than 75%, HO2S Bank 1 Sensor 1 reading greater than 1.2) when the DTC was set. If so, check for a possible lean condition.