Oxygen Sensor Heater

Oxygen Sensor Heater Test:

Oxygen Sensor Heater Circuit:

CIRCUIT DESCRIPTION:

The Oxygen (HO2S) has a built in heater. This heater has battery voltage whenever the ignition switch is turned "ON." The heater causes the H02S to produce a signal to the ECM. This allows for better fuel control during engine warm-up. No codes can be set if the heater portion of the H02S fails. However, since it is part of the H02S, it is necessary to replace the entire sensor if the heater is found to be faulty.

TEST DESCRIPTION: Numbers below refer to circled numbers on the diagnostic chart.

1. This checks for an open in the BLK/WHT wire.

2. This checks for an open or short to ground in the PNK wire between the ECM and H02S, or for a faulty H02S.

3. This checks for a faulty H02S, or for a faulty ECM.

DIAGNOSTIC AIDS:

No DTC's can be set if the heater portion of the HO2S fails. If the heater portion of the HO2S does fail, the entire HO2S must be replaced.
An intermittent failure may be caused by a poor connection, rubbed through wire insulation, or a wire broken inside the insulation. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal to wire connections before component replacement.