Quick answer: The P0112 code indicates that the Engine Control Module (ECM) detects an abnormally low voltage from the Intake Air Temperature (IAT) sensor circuit. This tricks the computer into reading unrealistically hot intake air, affecting the fuel mixture. While safe for short drives, prompt repair prevents poor fuel economy and engine performance issues.
Seeing a P0112 code on your diagnostic scanner means your car’s computer thinks the incoming engine air is extremely hot, even on a freezing morning. This happens when the signal returning from the air temperature circuit drops below normal operational levels. Below, you will find out what causes this issue, how it impacts your drive, and how to fix it step by step.
What Does P0112 Mean?
The Intake Air Temperature (IAT) sensor monitors the temperature of the air entering your engine. It works using a thermistor, which alters electrical resistance based on temperature: cold air results in high resistance and high signal voltage, whereas hot air results in low resistance and low signal voltage.
When the computer sets code P0112, it is receiving a voltage signal near zero volts. The system interprets this ultra-low voltage as an extremely high intake air temperature, often reading over 240°F (115°C). Because hot air is less dense, the engine computer attempts to compensate by reducing the amount of fuel delivered. This creates an overly lean air-fuel mixture that hurts engine operation, especially when starting the vehicle cold.
Symptoms
- Check Engine Light illuminated on the dashboard
- Difficulty starting or long cranking when the engine is cold
- Engine hesitation, stumbling, or rough idling
- Noticeable drop in fuel economy
- Black exhaust smoke due to incorrect air-fuel adjustments
Possible Causes
The most common mistake when dealing with P0112 is replacing the sensor immediately without checking the wiring first, as a rubbed wire shorting to ground causes this exact fault.
- Corroded, bent, or damaged pins inside the sensor harness connector
- Signal wire shorted directly to ground in the wiring harness
- Faulty Intake Air Temperature sensor with an internal electrical short
- Damaged main wiring harness running to the engine computer
- Faulty Engine Control Module (rare)
Check These Yourself Before Visiting a Mechanic
- Inspect the plug connection: Disconnect the wiring harness attached to the intake air tube or air filter box. Look for dirt, moisture, or green corrosion on the metal pins.
- Look for damaged wiring: Trace the wires coming out of the sensor plug for a few feet. Check for burnt, cut, or pinched insulation where wires might touch the metal engine block.
- Clean the connector: Spray electronic contact cleaner into both sides of the harness plug, let it dry, and reconnect it firmly to ensure proper electrical contact.
How to Fix It
- Connect an OBD-II scan tool and view the live data stream for the IAT sensor reading. Confirm if it shows an abnormally high temperature.
- Unplug the IAT sensor connector while monitoring live data. If the reading instantly drops to extreme cold (around -40°F), the wiring is healthy and the sensor has an internal short. Replace the sensor.
- If the reading stays stuck on extreme high temperature with the sensor unplugged, the signal wire is shorted to ground somewhere in the harness.
- Inspect and repair any chafe points, damaged wire insulation, or corroded ground connections along the circuit path.
- Clear the trouble codes using the scan tool and perform a road test to verify that the temperature reading updates normally.
Estimated Repair Costs (2026)
| Job | Parts ($) | Labor ($) |
|---|---|---|
| Standalone IAT Sensor Replacement | $20 – $60 | $40 – $80 |
| Integrated MAF/IAT Sensor Assembly | $110 – $280 | $50 – $100 |
| Wiring Harness / Short Circuit Repair | $10 – $30 | $90 – $180 |
| Diagnostic Fee | $0 | $80 – $150 |
Note: These are 2026 estimates in US dollars; costs vary by make and model.
Frequently Asked Questions
Can I drive with the P0112 code?
Yes, you can drive short distances safely, but it is not recommended for extended periods. The false temperature readings cause the computer to miscalculate fuel delivery, which leads to poor performance, engine misfires, and reduced fuel economy.
How do I clear the P0112 code?
You can clear the code using any basic OBD-II scan tool after completing the repair. If you clear the code without fixing the underlying short circuit or faulty sensor, the Check Engine Light will return as soon as you turn the key.
Is the IAT sensor separate or built into the MAF sensor?
It depends on your vehicle design. Many modern vehicles combine the IAT sensor inside the Mass Air Flow (MAF) sensor assembly, while older or turbocharged cars often use a standalone IAT sensor mounted directly on the intake ducting or manifold.