Chart C-1D Heated Oxygen Sensor Check

Diagnostic Chart:

Heated Oxygen Sensor Circuit:

CIRCUIT DESCRIPTION
The Heated Oxygen Sensor (H02S) has a built-in heater. This heater promotes the activation of the oxygen sensor to aid in improved fuel control during engine warm-up. The Engine Control Module (ECM) turns the heater "ON" (to allow the electric current to flow to the oxygen sensor heater) when the engine is running without a heavy load or a high speed condition.

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

1. This checks for an open in BLK/WHT wire.
2. This checks for an open or short to ground in the PNK/BLK wire between ECM and HO2S or for a faulty HO2S.
3. This checks for a faulty HO2S or for a faulty ECM.


DIAGNOSTIC AIDS
No Diagnostic Trouble Codes (DTCs) 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 malfunction 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.