P0112 OBD2 Code Guide
P0112 is a sensors diagnostic trouble code. Use this hub to understand the plain meaning, the first checks to run, and which vehicle-specific guides may be more useful before replacing parts.
Intake Air Temperature (IAT) Circuit Low Input
Code P0112 signifies that the Powertrain Control Module (PCM) is receiving an abnormally low voltage signal from the Intake Air Temperature (IAT) sensor. In most automotive systems, a low voltage signal from the IAT sensor corresponds to a very high intake air temperature reading. This discrepancy can lead the PCM to incorrectly calculate fuel delivery and ignition timing, potentially causing rich or lean conditions, poor fuel economy, reduced engine performance, and increased emissions. The underlying cause is typically a short circuit to ground within the IAT sensor circuit, a faulty IAT sensor itself, or, less commonly, an internal problem with the PCM.
Code verification standard
P0112 is published with SAE J2012 / ISO 15031-6 code structure plus OBD2 P0112 diagnostic context.
First checks
- - Read all stored and pending codes before clearing anything.
- - Save freeze-frame data so you know speed, load and temperature when the code set.
- - Inspect wiring, connectors, fuses, hoses and obvious leaks tied to the named system.
- - Compare live data against realistic values before buying sensors or modules.
- - Clear the code only after repair and complete a drive cycle to confirm it does not return.
P0112 diagnostic path
- 11. Perform a thorough visual inspection of the IAT sensor and its wiring harness. Look for any signs of physical damage, corrosion on the connector terminals, or chafed/pinched wires that could indicate a short to ground. Ensure the connector is securely seated.
- 22. Connect an OBD-II scan tool and monitor the live data stream for the IAT sensor reading. If the reading is excessively high (e.g., above 250°F or 120°C) even when the engine is cold or has been off for hours, it confirms the low voltage input. Compare this reading to the ambient air temperature.
- 33. Disconnect the IAT sensor connector. With the ignition ON (engine OFF), use a multimeter to check for the reference voltage (typically 5V) at the sensor connector's power supply wire. Also, check for good continuity to ground on the ground wire. If the reference voltage is absent or the ground is open, trace the wiring back to the PCM. If the signal wire shows a short to ground, this is the issue.
- 44. If the wiring and reference voltage are good, remove the IAT sensor and test its resistance using a multimeter. Submerge the sensor in ice water and then hot water, recording resistance values at different temperatures. Compare these readings to the manufacturer's specifications. A faulty sensor will exhibit incorrect resistance values or an open/short circuit internally.
Verify before repair
- - Replace the faulty Intake Air Temperature (IAT) sensor.
- - Repair or replace damaged, corroded, or shorted wiring in the IAT sensor circuit.
- - Clean corrosion from the IAT sensor connector and terminals to ensure good electrical contact.
- - If all other components are verified good, replace the Powertrain Control Module (PCM) (less common).
Vehicle-specific pages to check next
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