Draft guidance: awaiting Claude spot-check, qualified-mechanic review and named-editor approval. Do not use a fault code alone to replace parts.
P0112: Intake-air temperature sensor 1 circuit low input
The ECU is seeing abnormally low signal voltage from the IAT circuit.
What P0112 means
The ECU is seeing abnormally low signal voltage from the IAT circuit. With the common negative-temperature-coefficient sensor design, that usually appears to the ECU as implausibly hot intake air and often points to a short circuit. It does not automatically mean the incoming air is genuinely too hot.
Can I still drive?
Book diagnosis soon and limit driving until checked. A short trip may be reasonable if the lamp is steady amber and the vehicle runs normally. Stop for a flashing warning, rough running or stalling, unsafe power loss, smoke, overheating or a red warning.
Symptoms
- Engine-management light.
- Starting difficulty.
- Hesitation or reduced power.
- Altered fuel consumption.
- No noticeable change if the ECU substitutes a fallback value.
Common causes
- Signal wire shorted to earth.
- Internally shorted sensor.
- Damaged, contaminated or wet connector.
- Chafed loom.
- Fault within a combined MAF/MAP/IAT unit.
- Less commonly, a shared circuit or ECU fault.
Safe first checks
- With the ignition off, inspect the plug and loom for moisture, crushed insulation or contact with metal and hot parts. Preserve live data before clearing the code. An extreme high-temperature reading on a cold engine supports a circuit fault, although the displayed limit is manufacturer-specific. Do not assume actual hot intake air caused an electrical low-input code.
Typical UK fix cost
Estimated diagnostic charge: £60–£130. Estimated total with a separate sensor: £90–£230; with an integrated MAF/MAP/IAT unit: £180–£500. Connector or loom repair may be £130–£400+, with extensive harness damage costing more. Figures are indicative only.
Related models
This is a generic OBD-II code used across many makes and models. The exact test thresholds, component layout and repair route vary by engine and manufacturer, so check vehicle-specific technical information before ordering parts.
Related fault codes
- P0110: Intake-air temperature sensor 1 circuit
- P0111: Intake-air temperature sensor 1 circuit range/performance
- P0113: Intake-air temperature sensor 1 circuit high input
- P0115: Engine coolant temperature sensor 1 circuit
Sources
- Toyota repair-manual extract — P0112 low-input circuit behaviour
- HELLA — IAT resistance/voltage relationship and fault checks
- Start Rescue — UK independent-garage diagnostic-price context
A diagnostic trouble code identifies a system or circuit to investigate. It does not prove that a named part has failed. Preserve freeze-frame data and seek a vehicle-specific diagnosis before clearing the code.