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
- 1) DTC IS ACTIVE
Turn the ignition on.
With a scan tool, select View DTCs. Record DTC and Freeze Frame information.
Start the engine and allow it to idle for at least 60 seconds.
WARNING: When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts, or fan. Do not wear loose clothing. Failure to follow these instructions can result in personal injury or death.With a scan tool, select View DTCs.
Is the status Active for this DTC?
Yes
- Go to 2).
No
- Refer to *CHECKING FOR AN INTERMITTENT DTC .
- 2) (K41) O2 1/1 SIGNAL CIRCUIT
Turn the ignition off.
Disconnect the 1/1 Oxygen Sensor harness connector.
Turn the ignition on.
With a scan tool, read the 1/1 Oxygen Sensor voltage.
Is the 1/1 Oxygen Sensor voltage above 4.8 volts?
Yes
- Go to 3).
No
- Go to 5).
- 3) 1/1 OXYGEN SENSOR
Measure the voltage on the (K902) O2 Return (Up) circuit in the 1/1 Oxygen Sensor harness connector.
Is the voltage between 2.40 and 2.60 volts?
Yes
- Replace the 1/1 Oxygen Sensor.
- Perform *PCM VERIFICATION TEST .
No
- Go to 4).
- 4) (K902) O2 RETURN (UP) CIRCUIT SHORTED TO GROUND
Turn the ignition off.
Disconnect the Powertrain Control Module (PCM) harness connector.
Measure the resistance between ground and the (K902) O2 Return (Up) circuit in the 1/1 Oxygen Sensor harness connector.
Is the resistance below 100 ohms?
Yes
- Repair the (K902) O2 Return (Up) circuit for a short to ground.
- Perform *PCM VERIFICATION TEST .
No
- Go to 5).
- 5) (K41) O2 1/1 SIGNAL CIRCUIT SHORTED TO GROUND
Measure the resistance between ground and the (K41) O2 1/1 Signal circuit in the 1/1 Oxygen Sensor harness connector.
Is the resistance below 100 ohms?
Yes
- Repair the (K41) O2 1/1 Signal circuit for a short to ground.
- Perform *PCM VERIFICATION TEST .
No
- Go to 6).
- 6) (K41) O2 1/1 SIGNAL CIRCUIT SHORTED TO THE (K902) O2 RETURN (UP) CIRCUIT
Measure the resistance between the (K41) O2 1/1 Signal circuit and the (K902) O2 Return (Up) circuit in the 1/1 Oxygen Sensor harness connector.
Is the resistance below 100 ohms?
Yes
- Repair the short between the (K41) O2 1/1 Signal circuit and the (K902) O2 Return (Up) circuit.
- Perform *PCM VERIFICATION TEST .
No
- Go to 7).
- 7) POWERTRAIN CONTROL MODULE (PCM)
Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the 1/1 Oxygen Sensor 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 *PCM VERIFICATION TEST .
No
- Replace and program the Powertrain Control Module (PCM) in accordance with the Service Information.
- Perform *PCM VERIFICATION TEST .
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.
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