P0112: Intake Air Temperature Sensor Circuit Low Input
The P0112 code indicates that the Engine Control Module (ECM) has detected a voltage signal from the Intake Air Temperature (IAT) sensor that is lower than the expected range (typically below 0.2 volts). This usually means the sensor is reading an extremely high temperature (e.g., over 300°F) or there is a short to ground in the sensor circuit. The IAT sensor is a thermistor that changes resistance with temperature; low voltage suggests low resistance, which can be caused by a faulty sensor, wiring issues, or a short circuit. This code affects fuel mixture and ignition timing, potentially causing drivability problems.
01. Most Common Causes
- Faulty Intake Air Temperature (IAT) sensor
- Short to ground in the IAT sensor signal circuit
- Corroded or damaged IAT sensor connector
- Open or shorted wiring in the IAT sensor circuit
- ECM failure (rare)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Poor fuel economy
- Rough idle or stalling
- Hard starting (especially when cold)
- Black smoke from exhaust (rich mixture)
03. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data. Clear code and test drive to see if it returns.
Step 2: Visually inspect the IAT sensor connector and wiring for damage, corrosion, or shorts.
Step 3: Disconnect the IAT sensor and measure resistance across its terminals; compare to specifications (e.g., ~2.5kΩ at 68°F).
Step 4: Check voltage at the sensor connector with ignition on; should be about 5V reference and signal wire voltage varies with temperature.
Step 5: If sensor is good, test for shorts to ground or opens in the wiring between sensor and ECM.
Step 6: If all else fails, replace the IAT sensor and re-test.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
You can drive short distances, but it may cause poor performance, reduced fuel economy, and potential damage to the catalytic converter over time. It's best to diagnose and fix promptly.
How much does it cost to fix?▼
Typically between $50 and $150, including parts (IAT sensor $20-$50) and labor (0.5-1 hour). DIY replacement is often simple and cheaper.