Oxygen Sensor: Testing and Inspection

Chart C-1F:

Oxygen Sensor Circuit:

CIRCUIT DESCRIPTION:

The generator charging circuit supplies battery voltage to the heater part of the oxygen sensor. The heater warms the O2 sensor to allow a varying voltage to be produced by the O2 sensor more rapidly instead of waiting for the O2 sensor to heat-up on its own.

The following test procedures are for the heater part of the oxygen sensor. No malfunction codes will be logged if the heater fails to function properly.

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

1. This will verify that battery voltage is present for the heater.

2. This check will test the ground circuit to the heater.

3. This tests the heater element resistance. Resistance will vary with the temperature of the sensor. Normal resistance is between 3.5-14.2 ohms.

DIAGNOSTIC AIDS:

A poor or loose connection at the O2 sensor could result in a false code being set or the O2 heater not functioning properly. A shorted O2 sensor heater could cause a Code 13 to set.