What does it mean?
P1112 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: IAT Sensor Circuit Low Input (Intermittent) .
Symptoms
- Intermittent check engine light over several drive cycles
- Intake air temperature briefly showing an implausibly hot reading in live data
- Lean running during the fault, with hesitation and a flat spot on acceleration
- Light spark knock or pinging under load because timing is advanced for hot air
- Rough idle and, on some vehicles, hard starting when cold
- Reduced power that comes and goes without an obvious pattern
Likely causes
- Signal wire touching ground through a rubbed spot where the loom crosses the intake or a bracket
- Moisture in the connector creating a temporary path between the signal and ground pins
- Sensor with an internal short that appears when it is hot or vibrating
- Terminal partly bridging the sensor housing inside a damaged connector
- Harness pinched during a previous air filter or intake service
- Damaged sensor tip that has broken off and is contacting the housing
- Faulty combined mass airflow and temperature unit where the two are integrated
How to fix it
- Record the intake air temperature in live data during a road test and mark the moments it collapses to a high reading
- Unplug the sensor and confirm the displayed value moves to the opposite extreme, which proves the wiring and module respond
- With the sensor disconnected, measure resistance between the signal wire and ground while flexing the harness
- Inspect the connector for water, corrosion and a terminal that has moved out of position
- Check the sensor tip for damage or contamination and measure its resistance against the specification
- Repair the chafed harness section and re-route it away from sharp edges
- Replace the sensor if it shorts internally, then verify a stable reading through a complete warm-up and drive cycle