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
- DIAGNOSTIC TROUBLE CODE (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.
- Using the scan tool, select View DTCs.
Is the status Active for this DTC?
Yes
- Go To 2
No
- Perform the INTERMITTENT CONDITION diagnostic procedure. Refer to INTERMITTENT CONDITION .
- Start the engine and allow it to reach normal operating temperature.
- (K21) IAT SIGNAL CIRCUIT SHORTED TO VOLTAGE
- Turn the ignition off.
- Disconnect the Intake Air Temperature (IAT) Sensor harness connector.
- Disconnect the Powertrain Control Module (PCM) C2 harness connectors.
- Turn the ignition on.
- Measure the voltage of the (K21) IAT Signal circuit in the IAT Sensor harness connector.
Is there any voltage present?
Yes
- Repair the (K21) IAT Signal circuit for a short to voltage.
- Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
No
- Go To 3
- (K21) IAT SIGNAL OPEN OR HIGH RESISTANCE
- Turn the ignition off.
- Measure the resistance of the (K21) IAT Signal circuit between the IAT Sensor harness connector and the PCM C2 harness connector.
Is the resistance below 5.0 Ohms?
Yes
- Go To 4
No
- Repair the (K21) IAT Signal circuit for an open circuit or high resistance.
- Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
- (K900) SENSOR GROUND CIRCUIT OPEN OR HIGH RESISTANCE
- Measure the resistance of the (K900) Sensor Ground circuit between the IAT Sensor harness connector and the PCM C2 harness connector.
Is the resistance below 5.0 Ohms?
Yes
- Go To 5
No
- Repair the (K900) Sensor Ground circuit for an open circuit or high resistance.
- Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
- Measure the resistance of the (K900) Sensor Ground circuit between the IAT Sensor harness connector and the PCM C2 harness connector.
- INTAKE AIR TEMPERATURE SENSOR
- Turn the ignition off.
- Connect the Powertrain Control Module (PCM) C2 harness connectors.
- Connect a jumper wire between the (K21) IAT Signal circuit and the (K900) Sensor Ground in the IAT Sensor harness connector.
- Turn the ignition on.
- Using the scan tool, read the IAT Sensor signal voltage.
Is the voltage below 1.0 Volt with the jumper wire in place?
Yes
- Replace the Intake Air Temperature Sensor in accordance with the Service Information. Refer to SENSOR, AIR TEMPERATURE, INLET, REMOVAL .
- Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
No
- Go To 6
- POWERTRAIN CONTROL MODULE (PCM)
- Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Intake Air Temperature 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.
- Monitor the scan tool data relative to this circuit and wiggle test the wiring and connectors.
- Look for the data to change or for the DTC to reset during the wiggle test.
- Perform any Technical Service Bulletins that may apply.
Were any problems found?
Yes
- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
No
- Replace and program the Powertrain Control Module (PCM) in accordance with the Service Information. Refer to MODULE, POWERTRAIN CONTROL, REMOVAL .
- Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
NO RELATED
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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.