Code P0112: Definition and Explanation
The P0112 error code is a generic OBD-II code related to the powertrain. It indicates that the Powertrain Control Module (PCM) has detected an abnormally low voltage input from the Intake Air Temperature (IAT) sensor. Although generic, specific diagnostic procedures may vary depending on the vehicle’s make and model.
Role of the IAT (Intake Air Temperature) Sensor
The IAT sensor’s function is to measure the temperature of the air entering the engine. This data is crucial for the PCM, which uses it to regulate the air-fuel mixture and ignition timing. Warmer air is less dense, requiring adjustments to maintain optimal performance and low emissions. The sensor operates on the principle of a thermistor: its electrical resistance decreases as the temperature increases. The PCM sends a 5V reference voltage and interprets the returned voltage to determine the temperature.
Symptoms of Code P0112
Symptoms can be subtle or more pronounced:
- Illumination of the Malfunction Indicator Lamp (MIL) on the dashboard.
- Noticeable increase in fuel consumption.
- Rich air-fuel mixture (too much fuel).
- Hesitation, stalling, or engine knocking (detonation) during acceleration.
- Failure of the emissions test (high NOx emissions).
- Possibility of entering limp mode.
Possible Causes of Fault P0112
Several components can be the source of this code:
- Faulty IAT sensor: Internal failure, short circuit, or open circuit.
- Wiring issues: Signal wire shorted to ground, open or corroded power or ground wire.
- Defective connector: Oxidized, loose, or damaged pins on the sensor connector.
- Abnormally high temperatures: Overheated intake air (e.g., damaged air duct near the engine).
- PCM failure: Rare, but possible as a last resort.
Diagnosis and Solutions for Resolving P0112
Follow these steps to diagnose and repair the fault:
- Visual inspection: Inspect the sensor, its connector, and the wiring harness for damage, corrosion, or debris.
- Live data reading: Using an OBD2 scanner, observe the displayed IAT temperature value. At rest, with a cold engine, it should be close to the ambient temperature.
- Disconnection test: Unplug the sensor connector. The value read by the scanner should drop drastically (e.g., -40°C). If so, the sensor is most likely faulty and needs to be replaced.
- Continuity and short circuit test: If the value remains abnormally high after disconnection, use a multimeter to check for a possible short to ground on the signal wire. Also check the continuity of the power and ground wires.
- Replacement: After identifying the source of the problem, replace the faulty component (sensor, cable section) and clear the codes to ensure the fault does not return.
Related DTC Codes
Codes related to the IAT circuit: P0095, P0096, P0097, P0098, P0099, P0110, P0111, P0113, P0114.
Need Help?
Electrical diagnosis can be complex. If you are not equipped or confident, consult a professional mechanic for an accurate diagnosis and reliable repair.