P0112

Intake Air Temperature Circuit Low Input Bank 1

P0112 is a generic OBD-II powertrain diagnostic trouble code: Intake Air Temperature Circuit Low Input Bank 1. It is logged by the engine control unit when the air/maf monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.

Code
P0112
Group
Powertrain
System
Air/MAF
Severity
Warning (MIL on)
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What P0112 means

Code P0112 is set when the Powertrain Control Module (PCM) detects that the voltage signal from Intake Air Temperature (IAT) Sensor 1 has dropped below the expected minimum threshold — typically below approximately 0.1 V. Because the IAT sensor is a Negative Temperature Coefficient (NTC) thermistor, a very low voltage reading corresponds to an implausibly high indicated temperature (often above 150 °C / 302 °F), which the PCM recognises as an out-of-range circuit fault rather than a realistic air charge temperature.

The PCM uses IAT data to trim fuel delivery, ignition timing, and cold-start enrichment strategies. When P0112 is active, the PCM substitutes a default substitute value (commonly a fixed moderate temperature such as 20 °C), which degrades the accuracy of these calculations. In practice this tends to cause richer-than-necessary fuelling at cold start, reduced fuel economy, and possible light knock at high load because the ECU no longer knows the true density of the incoming air charge.

P0112 is the low-circuit companion to P0113 (circuit high / open). The most frequent root causes are a wiring short to ground between the sensor and PCM, a failed sensor that has internally shorted, or corroded connector pins that collapse the signal voltage. The fault must be present for a calibrated period across multiple drive cycles before the PCM stores a confirmed DTC and illuminates the MIL.

Common causes

Most-frequently reported root causes when P0112 is logged.

  • 1
    IAT sensor internal short circuit (failed NTC thermistor)
  • 2
    Signal wire shorted to ground or to chassis earth
  • 3
    Corroded, spread, or water-ingressed sensor connector pins
  • 4
    Damaged or chafed wiring harness between sensor and PCM
  • 5
    PCM pin corrosion or damaged PCM input circuit
  • 6
    Low or unstable reference voltage supply from PCM (5 V ref fault)
  • 7
    Contaminated sensor element (oil from PCV blow-by or clogged air filter)

Symptoms drivers notice

MIL (Check Engine Light) illuminated
Reduced fuel economy due to PCM using a fixed substitute temperature value
Hesitation or stumble during cold-start warm-up
Possible light engine knock or ping under high load (timing not retarded for hot charge)
Slightly rich idle or black smoke at cold start on some vehicles
Hard start in very cold ambient conditions on affected calibrations

How to diagnose P0112

A typical diagnostic flow when this code is present.

  1. 1
    Connect a scan tool and record the live IAT PID value — a reading above 130 °C (266 °F) with the engine cold confirms a low-voltage circuit fault
  2. 2
    Inspect the IAT sensor connector and wiring harness for corrosion, spread pins, chafing, or contact with hot engine components; repair any damage found
  3. 3
    With key-on engine-off and the sensor connector disconnected, verify approximately 5 V reference on the signal wire at the harness side; absence indicates a PCM reference fault or open in the supply circuit
  4. 4
    Measure resistance across the IAT sensor terminals with a multimeter and compare to the manufacturer temperature–resistance chart (a healthy NTC sensor at 20 °C typically reads 2–3 kΩ); a near-zero reading indicates an internal sensor short
  5. 5
    Back-probe or use a breakout box to check for a short to ground on the signal wire between connector and PCM; a short to ground confirms a wiring fault rather than a sensor fault
  6. 6
    Replace the IAT sensor if wiring and connector integrity are confirmed good, then clear the DTC and perform a complete drive cycle to verify the repair
  7. 7
    If the code returns immediately after sensor and wiring repair, inspect the PCM connector for pin corrosion and test PCM output reference voltage

Related powertrain codes

Frequently asked questions

Can I drive with a P0112 code active?

The vehicle is generally drivable in the short term because the PCM substitutes a default temperature value, but you may notice reduced fuel economy, slight hesitation, or light knock under load. Prolonged driving with a faulty IAT signal can accelerate engine wear through sub-optimal fuelling and timing, so the fault should be diagnosed promptly.

Is P0112 the same as a bad IAT sensor, or could it be wiring?

P0112 specifically indicates a low-voltage (shorted) circuit condition, not an open circuit. While a failed sensor with an internal short is a common cause, a signal wire that has chafed against the chassis or a corroded connector pin can produce exactly the same code. Always inspect the wiring and connector before condemning the sensor itself.

How is P0112 different from P0113?

Both codes relate to the same IAT Sensor 1 circuit. P0112 (circuit low) means the signal voltage is too low — indicating a short to ground or an internally shorted sensor. P0113 (circuit high) means the signal voltage is too high — indicating an open circuit, a broken sensor wire, or a sensor that has failed open. Diagnosing them requires opposite electrical tests.

Will clearing the code fix P0112?

Clearing the DTC without repairing the underlying fault will only temporarily extinguish the MIL. The PCM monitors the IAT circuit continuously and will re-set P0112 within one or two drive cycles if the root cause — shorted sensor, grounded signal wire, or corroded connector — has not been corrected.

Disabling P0112 in software

RaceTune can permanently disable P0112 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.

Permanent
The monitor is disabled in the ECU itself — not just cleared. It cannot return.
Tailored to your file
Each patch is matched to your specific software version — never a one-size-fits-all file.
Reversible
The original file is always preserved. Reflash the stock to return the ECU to factory state.

Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.

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