P0072 — Ambient air TEMP.sensor low

Causes

• Short to ground in AAT sensor wiring
• Faulty ambient air temperature sensor (thermistor)
• Poor or corroded connector/pins at sensor or ECU
• Open or shorted harness between sensor and ECU
• Incorrect reference/pull-up voltage from ECU
• Intermittent connection (water ingress, damaged insulation)

Symptoms

• Malfunction Indicator Lamp (MIL) may be illuminated
• Ambient outside temperature readout incorrect or pegged at an extreme value on dash
• Possible impact on climate control behavior (auto HVAC uses outside temp)
• No noticeable change in engine drivability in most cases

What to check

• Visually inspect AAT sensor location (front bumper/air inlet) for damage, debris, or water intrusion
• Check connector for corrosion, bent pins, pushed-out terminals or loose fit
• Measure sensor connector voltage with ignition ON (back-probe)
• Measure sensor resistance vs ambient air temperature with sensor removed
• Inspect wiring harness for chafing, pinches, or repairs, especially near front end and grille
• Scan for related codes (IAT, other temperature sensors) and freeze-frame data

Signal parameters

• Typical AAT sensor is an NTC thermistor in a voltage-divider to ECU (ECU supplies reference/pull-up ~5 V or internal circuit)
• Normal sensor voltage range (varies by vehicle): roughly 0.3–4.7 V depending on ambient temperature (low voltage indicates low input fault if below ECU threshold)
• Typical resistance example for common 10 kΩ NTC: ≈10 kΩ at 25 °C (manufacturer-specific — consult vehicle service data)
• Fault condition detected when sensor voltage is lower than ECU’s programmed threshold (often

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