P0072

What it means

P0072 means the powertrain control module has seen the signal from the ambient air temperature sensor fall below the expected range, which points to a short to earth or a very low voltage on the circuit. The module sees an implausibly high temperature reading, or a signal that is lower than the sensor could normally produce. The code is stored when this persists for the module's set time.

Symptoms

• Engine warning light on
• Incorrect or fixed outside temperature reading on the dashboard (often very hot)
• Automatic climate control not working properly or defaulting to a fixed setting
• Slightly rough cold starts or altered idle on some models
• Poor fuel economy or altered fan operation on some models

Possible causes

• Faulty ambient air temperature sensor with an internal shortlikely
• Sensor signal wire chafed and shorted to earthlikely
• Corroded, wet or damaged sensor connector causing a low signallikely
• Damaged sensor wiring from impact, road debris or previous front-end repairpossible
• Short between the signal circuit and the sensor earth within the harnesspossible
• Faulty powertrain control module input circuitrare

How to diagnose

1. Read all stored codes and freeze frame data, noting the conditions when the fault was set, then check for other temperature sensor codes
2. Compare the ambient temperature shown on live data with the dashboard reading and the real outside temperature
3. Inspect the sensor, which is usually behind the front bumper or grille, and its connector for damage, water ingress and corrosion
4. Check the wiring along its route for chafing, melting or crush damage, particularly near the bumper and radiator area
5. Unplug the sensor and watch live data: the reading should change to a very cold or default value if the wiring is good, while a sensor-end resistance check against the manufacturer's temperature table shows if the sensor is faulty
6. With the sensor unplugged and the ignition on, check the reference voltage at the connector and check the signal wire for a short to earth, using the model's wiring diagram
7. Check the continuity and insulation of the harness between sensor and control module, and check module connector pins for damage
8. Clear the code and road test to see whether it returns

How to fix

• Replace the ambient air temperature sensor if its resistance is out of specification
• Repair or replace the damaged or shorted section of wiring
• Clean or replace the corroded or damaged connector and terminals, and seal against moisture
• Repair the harness short between signal and earth circuits
• Diagnose and replace or repair the control module only after all wiring and sensor faults are ruled out

Can I keep driving?

Nearby codes

• P0071GenericAmbient Air Temperature Sensor Circuit A Range/Performance
• P0073GenericAmbient Air Temperature Sensor Circuit A High