P0141-O2 SENSOR 1/2 HEATER PERFORMANCE

For a complete wiring diagram Refer to Section 8W.

Theory of Operation

The PCM performs a continuous check of the O2 sensor heater circuit during operation. The heater circuit is momentarily disabled to allow a resistance measurement to be taken to infer heater temperature. The current delivery to the heater is duty cycled to maintain a specific target temperature. The error from the target temperature is continuously monitored to assess heater performance.

When Monitored:
With the engine running, O2 sensor heater duty cycle greater than 0%, and battery voltage greater than 11.0 volts.
Set Condition:
The PCM detects no O2 sensor output when the heater is powered up. Two trip fault. Three good trips to turn off the MIL.

Possible Causes

(K299) O2 1/2 HEATER CONTROL CIRCUIT OPEN OR HIGH RESISTANCE

(Z924) GROUND CIRCUIT OPEN OR HIGH RESISTANCE

OXYGEN SENSOR 1/2

POWERTRAIN CONTROL MODULE (PCM)

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).

Diagnostic Test

1.OXYGEN SENSOR 1/2 HEATER CONTROL OPERATION

NOTE: Wait a minimum of 8 minutes to allow the sensor to cool down before continuing. The sensor voltage should stabilize between 4.6 and 5.0 volts.

Does the voltage stay above 4.5 volts?

Yes

Go to 2

Refer to the *CHECKING FOR AN INTERMITTENT DTC Diagnostic Procedure. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)

2.OXYGEN SENSOR 1/2

NOTE: Allow the O2 sensor to cool down to room temperature.

NOTE: The O2 heater element resistance should be measured at 70° F (21.1° C). The resistance value will vary at different temperatures.

Is the resistance between 2.0 and 30.0 ohms?

Yes

Go to 3

Replace the Oxygen Sensor 1/2 in accordance with the Service Information.
Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).

3.(K299) O2 1/2 HEATER CONTROL CIRCUIT OPEN OR HIGH RESISTANCE

Is the resistance below 0.5 ohm?

Yes

Go to 4

Repair the (K299) O2 1/2 Heater Control circuit for an open circuit or high resistance.
Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).

4.(Z924) GROUND CIRCUIT OPEN OR HIGH RESISTANCE

NOTE: The test light should be illuminated and bright. Compare the brightness to that of a direct connection to the battery.

Is the test light illuminated and bright?

Yes

Go to 5

Repair the (Z924) Ground circuit for an open circuit or high resistance.
Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).

5.POWERTRAIN CONTROL MODULE (PCM)

Were any problems found?

Yes

Repair as necessary.
Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).

Replace and program the Powertrain Control Module (PCM) in accordance with the Service Information.
Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).