O2 Sensor 1/1 Heater Circuit Low

P0135 - O2 SENSOR 1/1 HEATER CIRCUIT LOW





When Monitored and Set Condition

- 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.





For a complete Powertrain Control Module Circuit Diagram, Schematics and Diagrams.

Diagnostic Test

1. PRE-DIAGNOSTIC CHECK OUT

NOTE: Always perform diagnostics with a fully charged battery.

NOTE: Check connectors - Clean/repair as necessary. Poor pin to terminal connections can set DTCs.

NOTE: Check for applicable TSBs related to the problem.

Turn the ignition on.
With the scan tool, 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.

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

Yes

- Go To 3

No

- Replace the Oxygen Sensor. Removal.
- Perform POWERTRAIN VERIFICATION TEST - VER 2. Powertrain Verification Test

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.
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.Powertrain Control Module - Removal.
- Perform POWERTRAIN VERIFICATION TEST - VER 2. Powertrain Verification Test

No

- Repair the O2 Heater Control circuit for a short to ground.
- Perform POWERTRAIN VERIFICATION TEST - VER 2. Powertrain Verification Test