What is the P0072 code?
The P0072 error code indicates a problem with the Ambient Air Temperature (AAT) sensor circuit low. This generic powertrain diagnostic code applies to most OBDII-equipped vehicles but is more common in Audi, BMW, Chrysler, Dodge, Ford, Jeep, Mazda, Mitsubishi, VW, and Volvo.
Role of the Ambient Air Temperature (AAT) Sensor
The AAT sensor converts the outside air temperature into an electrical signal sent to the Powertrain Control Module (PCM). This data is essential for:
- Regulating the operation of the automatic climate control system.
- Displaying the outside temperature on the dashboard or console.
The PCM compares the AAT sensor signal with those from the Intake Air Temperature (IAT) sensor and the Engine Coolant Temperature (ECT) sensor at startup, after a period of inactivity. The P0072 code is triggered if an abnormal discrepancy is detected between these values.
Symptoms of the P0072 Code
- Malfunction Indicator Lamp (MIL) illuminated
- Poor air conditioning performance
- Inaccurate outside temperature display on the dashboard
- Incorrect display on the overhead console
Possible Causes
- Connection issue or exposed wire in the signal circuit
- Ground problem at the AAT sensor
- Faulty AAT sensor
- PCM failure (rare)
Diagnosis and Solutions
1. Check Technical Service Bulletins (TSBs)
First, consult your manufacturer’s TSBs. A known fix may exist for your model, saving you time and money.
2. Visual Inspection
Locate the AAT sensor, usually positioned in front of the radiator. Inspect the connectors and wiring for any signs of wear, corrosion, or burning. Clean the terminals with electrical contact cleaner and apply dielectric grease.
3. Sensor Testing
Using a digital multimeter (DVOM), measure the sensor’s resistance (ohms) and compare it to reference values for the ambient temperature. A resistance of 0 Ω or infinite (OL) indicates a faulty sensor.
4. Circuit Testing
Using a scan tool, check the AAT sensor’s signal voltage. It should be around 5 volts. Jumpering the connector terminals should drop the voltage to near 0 volts. No change indicates a wiring issue or faulty PCM.
5. Replacement
If all previous tests are conclusive, replace the AAT sensor. If the problem persists, consult a professional for a thorough diagnosis, as the PCM may require reprogramming.
Conclusion
The P0072 code is often related to faulty connections or a malfunctioning AAT sensor. A visual inspection and simple tests can often resolve the issue. For an accurate diagnosis or if you are not comfortable performing these procedures, consult a qualified mechanic.
Need help? Equip yourself with a reliable scan tool to diagnose your vehicle yourself or find a professional near you.