P0112

What it means

P0112 means the engine control unit has seen the signal voltage from intake air temperature sensor 1 fall below the expected range, which it reads as a circuit low fault. A low voltage reading equates to a very high temperature, often beyond what is plausible for intake air. The code is usually set by a short to earth in the signal wiring or a faulty sensor.

Symptoms

• Check engine light on
• Hard starting, especially when cold
• Rough idle or hesitation
• Poor fuel economy or richer running than normal
• Black smoke from the exhaust in some cases
• Reduced power if the control unit uses a default air temperature value

Possible causes

• Faulty intake air temperature sensor with an internal shortlikely
• Signal wire shorted to earth or chafed against bodyworklikely
• Damaged, corroded or wet sensor connector or terminalslikely
• Sensor combined with the mass airflow sensor or manifold pressure sensor has failed (depends on model and engine)possible
• Signal and sensor earth wires shorted together in the harnesspossible
• Fault inside the engine control unitrare

How to diagnose

1. Read the freeze frame data and note the intake air temperature, coolant temperature and engine load when the code set, and check for other stored codes.
2. Compare the live intake air temperature with coolant temperature on a cold engine; they should be close, and an implausibly high reading points to a circuit low condition.
3. Inspect the sensor, connector and wiring for damage, chafing, corrosion, water ingress and signs of previous repairs.
4. Unplug the sensor with the ignition on and watch the live data; the reading should go to a very low temperature if the wiring and control unit are sound.
5. Check the sensor resistance against the manufacturer's temperature specification, as the layout depends on whether it is a standalone sensor or part of another sensor.
6. Check the signal wire for a short to earth and for continuity with the control unit connector unplugged, following the wiring diagram for the model.
7. Check the control unit reference voltage and earth at the sensor connector.

How to fix

• Replace the intake air temperature sensor, or the combined sensor assembly where it is not sold separately.
• Repair or replace chafed or shorted wiring, and secure it clear of sharp edges and hot components.
• Clean or replace corroded connector terminals and ensure the connector locks properly.
• Dry out and seal the connector if water has entered, and fix the source of the water ingress.
• Diagnose and repair or replace the control unit only after wiring and sensor faults have been fully ruled out.

Can I keep driving?

Nearby codes

• P0111GenericIntake Air Temperature Sensor 1 Circuit Range/Performance Bank 1
• P0113GenericIntake Air Temperature Sensor 1 Circuit High Bank 1