O2 Sensor 1/1 Heater Circuit Low

P0135 - O2 SENSOR 1/1 HEATER CIRCUIT LOW

P0135 - O2 Sensor 1/1 Heater Circuit Low:

WHEN MONITORED
Engine Running and Heater duty cycle greater than 0%

SET CONDITION
The PCM detects the O2 Heater voltage is out of acceptable range. Below 0.0926 volt.

POSSIBLE CAUSES
- O2 heater control short to ground
- O2 heater element
- Powertrain control module


DIAGNOSTIC TEST




1. PRE-DIAGNOSTIC CHECK OUT

NOTE:
- Always perform diagnostics with a fully charged battery.
- Check connectors - Clean/repair as necessary. Poor pin to terminal connections can set DTCs.
- Check for applicable TSBs related to the problem.

Turn the ignition on.
With the DRB III(R), read PCM DTCs.
Using the wiring diagram/schematic as a guide, inspect the wiring and connectors.
Repair as necessary.
Perform this procedure prior to symptom diagnosis.
Continue
Go To 2




2. O2 HEATER ELEMENT

NOTE:
- Check the Engine Control Fuse 2 in the Relay Control Module. If it is open, multiple DTCs will be set in the PCM. Determine the cause of the open fuse before continuing using the wiring diagrams/ schematics as a guide.
- Allow the O2 Sensor to cool down to room temperature.

Turn the ignition off.
Disconnect the O2 Sensor harness connector.

NOTE: Check connectors - Clean/repair as necessary.

Measure the resistance of the O2 Sensor Heater element at the O2 Sensor harness connector.

Q: Is the O2 Sensor Heater element resistance between 8.5 and 9.5 ohms?

YES: Go To 3

NO: Replace the Oxygen Sensor.
Perform POWERTRAIN VERIFICATION TEST - VER 2. Powertrain Verification Test - Ver 2




3. O2 HEATER CONTROL CIRCUIT SHORT TO GROUND

With the ignition off.

Disconnect the PCM harness connectors.

NOTE: Check connectors - Clean/repair as necessary.

Measure the resistance between ground and the O2 Heater Control circuit.

Q: Is the resistance above 100 kohms?

YES: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as
Necessary. Replace and program the Powertrain Control Module.
Perform POWERTRAIN VERIFICATION TEST - VER 2. Powertrain Verification Test - Ver 2

NO: Repair the O2 Heater Control circuit for a short to ground.
Perform POWERTRAIN VERIFICATION TEST - VER 2. Powertrain Verification Test - Ver 2