Meaning

The intake air temperature (IAT) sensor signal voltage is below the minimum acceptable threshold. An excessively low voltage corresponds to an unrealistically high temperature reading, or indicates a short to ground in the sensor circuit.

Common causes

• Short to ground on the IAT sensor signal wire
• Internally shorted IAT sensor
• Corroded connector or shorted contacts
• Damaged wiring between sensor and ECU
• ECU fault (rare)

Symptoms

• Check-engine light (MIL) on
• Incorrect air/fuel mixture (excessively rich when cold)
• Poor cold-start performance
• Increased fuel consumption
• Possible black smoke from the exhaust

Severity

What to do

1. Measure IAT signal voltage at the connector: should be 0.5–4.5 V at ambient temperature
2. Check IAT sensor resistance (typically 2–3 kΩ at 20 °C)
3. Inspect wiring for shorts to ground
4. Check the connector for corrosion or deformed contacts
5. Replace the IAT sensor if out of specification

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