What causes fault code P0070?

• Most likely: Faulty Ambient Air Temperature (AAT) sensor • Likely: Corrosion or moisture in the sensor connector (common due to location near the front bumper) • Possible: Wiring harness open circuit or short to ground/power • Rare: Internal PCM/ECU failure or Body Control Module (BCM) fault

Powertrain (Engine & Gearbox)Standard EOBD

P0070 - Ambient Air Temperature Sensor Circuit

Q: What are the symptoms of fault code P0070?

• Check engine light (MIL) illuminated • Incorrect outside temperature display on the dashboard (often showing extreme values or dashes) • Air conditioning (AC) performance issues or inoperative compressor • Problems with automatic defrost functions • Potential emissions test failure in some jurisdictions

Q: How do you fix fault code P0070?

STEP 1: Visually inspect the sensor and connector for physical damage or corrosion. Clean contacts if necessary. STEP 2: Use a scan tool to monitor the AAT live data stream. Compare the reading with actual ambient temperature. STEP 3: Check for 5V reference voltage and ground at the sensor connector with the ignition ON. Measure sensor resistance (typically 2k-5k Ohms at 20°C/68°F depending on OEM specs). STEP 4: Replace the sensor if it is out of tolerance. If wiring is faulty, repair using weather-sealed connectors.

Last updated:1 February 2026

Related:Ambient Air Temperature (AAT) Sensor, Engine Control Module (ECM), HVAC Control Module, Wiring Harness

System

Powertrain (Engine & Gearbox)

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Technical Description

P0070 is a diagnostic trouble code (DTC) for a malfunction within the Ambient Air Temperature (AAT) sensor circuit. The Powertrain Control Module (PCM) monitors the voltage signal from the AAT sensor to adjust engine performance parameters and HVAC operations. The sensor is typically an NTC thermistor. If the signal voltage remains outside the calibrated range (typically 0.1V to 4.9V) for a set duration, the PCM triggers P0070. This fault can impact air density calculations, intake air temperature monitoring, and in some diesel applications, it may inhibit DPF regeneration.

Possible Causes

Faulty Ambient Air Temperature (AAT) sensor

Corrosion or moisture in the sensor connector (common due to location near the front bumper)

Wiring harness open circuit or short to ground/power

Internal PCM/ECU failure or Body Control Module (BCM) fault

Symptoms

Check engine light (MIL) illuminated

Incorrect outside temperature display on the dashboard (often showing extreme values or dashes)

Air conditioning (AC) performance issues or inoperative compressor

Problems with automatic defrost functions

Potential emissions test failure in some jurisdictions

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P0070 - Ambient Air Temperature Sensor Circuit

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P0070 - Ambient Air Temperature Sensor Circuit

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