What it means
The IAT signal voltage is below threshold, which the ECU interprets as an implausibly hot intake (low NTC resistance). Usually a wiring short to ground or a failed sensor.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Intake air temperature sensor 1 measures the temperature of incoming air, and its signal helps the ECU adjust engine management for air density. The ECU interprets a low circuit input as an implausibly hot intake; P0112 sets when that signal falls below its threshold, commonly because the signal wire is grounded or the sensor has failed internally.
Common causes
Most likely first.
- Signal wire shorted to ground
- Sensor failed shorted internally
Symptoms
- Check engine light on
- Hard starting or rough running
- Reduced fuel economy
How to diagnose it
- Review freeze-frame data and compare IAT sensor 1's live reading with ambient temperature to confirm that it indicates implausibly hot air.
- Inspect sensor 1's connector and wiring for a damaged terminal or signal insulation rubbed through to ground.
- Check whether sensor 1 is integrated into the MAF and inspect the shared connector and harness if it is.
- With vehicle service information, test the sensor 1 signal circuit for a short to ground and check its connections.
- Measure sensor 1 and its circuit against the manufacturer's specification to determine whether the sensor or wiring is pulling the signal low.
Common fixes
- Repair a signal wire shorted to ground in the sensor 1 circuit.
- Clean or repair damaged or corroded terminals at the IAT sensor 1 connector.
- Replace sensor 1 if it has failed internally and the wiring is intact.
- Replace the combined MAF/IAT assembly if testing confirms the integrated sensor 1 has failed.
Can I keep driving?
If the engine runs normally, short necessary trips may be possible, but cold starting, drivability, or fuel economy can worsen. Avoid driving if rough running or stalling makes control difficult, and arrange repair because the ECU is receiving a falsely hot intake temperature.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.