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
- DTC IS ACTIVE
- Start the engine and allow it to reach normal operating temperature.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 may result in possible serious or fatal injury.
- With the scan tool, select View DTCs.
Is the status Active for this DTC?
Yes
- Go to step 2
No
- Refer to the CHECKING FOR AN INTERMITTENT DTC Diagnostic Procedure. See DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure .
- Start the engine and allow it to reach normal operating temperature.
- (K99) O2 1/1 HEATER CONTROL CIRCUIT SHORTED TO VOLTAGE
- Turn the ignition off.
- Disconnect the Oxygen Sensor 1/1 connector.
- Disconnect the Powertrain Control Module (PCM) connector.
- Turn the ignition on.
- Measure the voltage of the (K99) O2 1/1 Heater Control circuit in the Oxygen Sensor 1/1 harness connector.
Is there any voltage present?
Yes
- Repair the (K99) O2 1/1 Heater Control circuit for a short to voltage.
- Perform the PCM VERIFICATION TEST. See DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure .
No
- Go to step 3
- (K99) O2 1/1 HEATER CONTROL CIRCUIT OPEN OR HIGH RESISTANCE
- Measure the resistance of the (K99) O2 1/1 Heater Control circuit between the Oxygen Sensor 1/1 harness connector and the Powertrain Control Module (PCM) harness connector.
Is the resistance below 5.0 ohms?
Yes
- Go to step 4
No
- Repair the (K99) O2 1/1 Heater Control circuit for an open circuit or high resistance.
- Perform the PCM VERIFICATION TEST. See DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure .
- Measure the resistance of the (K99) O2 1/1 Heater Control circuit between the Oxygen Sensor 1/1 harness connector and the Powertrain Control Module (PCM) harness connector.
- OXYGEN SENSOR 1/1
- Connect the Powertrain Control Module (PCM) connector.
- Turn the ignition on.
- With the scan tool, actuate the Oxygen Sensor 1/1 control to the ON (100%) position.
- Using a 12 volt test light connected to ground, check the (K99) O2 1/1 Heater Control 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.
- With the scan tool, actuate the Oxygen Sensor 1/1 control to the OFF (0%) position.
- Using a 12 volt test light connected to ground, check the (K99) O2 1/1 Heater Control circuit in the Oxygen Sensor 1/1 harness connector.NOTE: The test light should not be illuminated.
Is the test light illuminated and bright with the actuator ON (100%) and not illuminated with the actuator OFF (0%)?
Yes
- Replace the Oxygen Sensor 1/1 in accordance with the Service Information.
- Perform the PCM VERIFICATION TEST. See DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure .
No
- Go to step 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 (TSBs) that may apply.
Were any problems found?
Yes
- Repair as necessary.
- Perform the PCM VERIFICATION TEST. See DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure .
No
- Replace and program the Powertrain Control Module (PCM) in accordance with the Service Information.
- Perform the PCM VERIFICATION TEST. See DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure .
NO RELATED
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Affiliate disclosure: We may earn a commission at no extra cost to you.
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.