P0135-O2 SENSOR 1/1 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

(K99) O2 1/1 HEATER CONTROL CIRCUIT OPEN OR HIGH RESISTANCE

(Z916) GROUND CIRCUIT OPEN OR HIGH RESISTANCE

OXYGEN SENSOR 1/1

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 1/1 HEATER CONTROL OPERATION

Turn the ignition off.

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.

Turn the ignition on.
With a scan tool, actuate the Oxygen Sensor 1/1 control.
With the scan tool, monitor Oxygen Sensor 1/1 voltage for at least 2 minutes.

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 1/1

Turn the ignition off.

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

Disconnect the Oxygen Sensor 1/1 harness connector.
Measure the resistance of the O2 sensor heater element across the Oxygen Sensor 1/1 connector between the heater control terminal and the ground terminal.

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

3. (K99) O2 1/1 HEATER CONTROL CIRCUIT OPEN OR HIGH RESISTANCE

Disconnect the Powertrain Control Module (PCM) harness connector.
Measure the resistance of the (K99) O2 1/1 Heater Control circuit from the Oxygen Sensor 1/1 harness connector to the Powertrain Control Module (PCM) harness connector.

Is the resistance below 0.5 ohm?

Yes

Go to 4

Repair the (K99) O2 1/1 Heater Control circuit for an open circuit or high resistance.
Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).

4. (Z916) GROUND CIRCUIT OPEN OR HIGH RESISTANCE

Using a 12 volt test light connected to 12 volts, check the (Z916) Ground circuit in the Oxygen Sensor 1/1 harness connector.

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 (Z916) 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)

Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Oxygen Sensor 1/1 and the Powertrain Control Module (PCM).
Look for any chafed, pierced, pinched, or partially broken wires.
Look for broken, bent, pushed out or corroded terminals.
Refer to any Technical Service Bulletins that may apply.

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).