Chart C-1D Heated Oxygen Sensor (HO2S) Heater Check

Chart C-1D:

Heated Oxygen Sensor Circuit:

CIRCUIT DESCRIPTION
The Heated Oxygen Sensor (HO2S) has a self contained heater element. The function of the heater is to bring the oxygen sensor up to operating temperature for earlier "Closed Loop" operation. This heating element is energized with ignition "ON."

CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.

1. Perform Tech 1 test if available.
2. Use this test if Tech 1 test is unavailable
3. Checks for ignition voltage to heater element.
4. Checks resistance of the heater element.

DIAGNOSTIC AIDS
The heater function of the HO2S can be tested by the following procedure:
- Remove the 15 amp ERLS fuse (I/P fuse block).
- Install Tech 1. Ignition "ON" enter parameter list (FO). Scroll to Bank 1 & Bank 2 HO2S.
- With HO2S at room temperature (scan tool should display approximately 450mV).
- Install 15 amp ERLS fuse.
- Observe HO2S voltage. Voltage should steadily drop to approximately 100mV. If voltage does not drop, replace the sensor