Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Diagnostic Test
- O2 SENSOR 1/1 HEATER OPERATION
- Turn the ignition off.NOTE:
Wait a minimum of eight minutes to allow the O2 Sensor to cool down before continuing the test. Allow the O2 Sensor voltage to stabilize between 4.6 and 5.0 Volts.
- Ignition on, engine not running.
- With the scan tool, actuate the O2 Sensor 1/1 Heater Test.
- Using the scan tool, monitor O2 Sensor 1/1 voltage for at least two minutes.
Does the voltage stay above 4.5 Volts?
Yes
- Go To 2.
No
- Perform the INTERMITTENT CONDITION diagnostic procedure. Refer to INTERMITTENT CONDITION .
- Turn the ignition off.
- O2 SENSOR 1/1 HEATER ELEMENT
- Turn the ignition off.NOTE:
Allow the O2 sensor to cool down to room temperature.
- Disconnect the O2 Sensor 1/1 harness connector.
- Measure the resistance of the O2 Sensor 1/1 Heater Element across the O2 Sensor, between the O2 Heater Control terminal and the Heater ground terminal.NOTE:
O2 Sensor 1/1 Heater Element resistance values should be measured at 21.1° C (70° F). The resistance value will vary with different temperature values.
Is the resistance of the O2 Sensor 1/1 Heater Element between 2.0 and 30.0 Ohms?
Yes
- Go To 3.
No
- Verify that there is good pin to terminal contact in the Sensor and Control Module connectors. If OK, replace the O2 Sensor. Refer to SENSOR, OXYGEN, REMOVAL .
- Perform the POWERTRAIN VERIFICATION TEST. Refer to PCM VERIFICATION TEST .
- Turn the ignition off.
- (K99) O2 SENSOR 1/1 HEATER CONTROL CIRCUIT OPEN
- Disconnect the PCM C2 harness connector.
- Measure the resistance of the (K99) O2 Sensor 1/1 Heater Control circuit from the O2 Sensor 1/1 harness connector to the PCM C2 harness connector.
Is the resistance below 0.5 Ohm?
Yes
- Go To 4.
No
- Repair the excessive resistance in the (K99) O2 Sensor 1/1 Heater Control circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Refer to PCM VERIFICATION TEST .
- (Z902) O2 SENSOR 1/1 HEATER GROUND CIRCUIT OPEN
- Measure the resistance between ground and the (Z902) O2 Sensor 1/1 Heater ground circuit in the O2 Sensor harness connector.
Is the resistance below 0.5 Ohm?
Yes
- Go To 5.
No
- Repair the excessive resistance in the (Z902) O2 Sensor 1/1 Heater ground circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Refer to PCM VERIFICATION TEST .
- Measure the resistance between ground and the (Z902) O2 Sensor 1/1 Heater ground circuit in the O2 Sensor harness connector.
- 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. Verify that there is good pin to terminal contact in the Sensor and Control Module connectors.
- Perform any Technical Service Bulletins that may apply.
Were there any problems found?
Yes
- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. Refer to PCM VERIFICATION TEST .
No
- Replace and program the Powertrain Control Module in accordance with the Service Information. Refer to MODULE, POWERTRAIN CONTROL, REMOVAL .
- Perform the POWERTRAIN VERIFICATION TEST. Refer to PCM VERIFICATION TEST .
NO RELATED
Use the Manual With the Right Hardware
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.