P0112 - Intake Air Temperature Circuit Low Input
P0112 is an intake-air or engine-coolant temperature sensor/circuit fault. Separate false sensor data from a real temperature problem before replacing parts.
Code first. Confirm symptoms and checks before pricing parts.
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Common Next Steps
Turn the code into the next check.
Check coil boots, carbon tracking, and whether the miss follows a swap.
Inspect gap, fouling, wear, oil, coolant, and plug-well condition.
Move to injector balance, pulse, or leak-down checks if the misfire stays.
Use compression or leak-down testing when spark and fuel checks do not move the fault.
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Code Overview
P0112 is an intake-air or engine-coolant temperature sensor/circuit fault. Separate false sensor data from a real temperature problem before replacing parts.
Common Causes
- IAT or ECT sensor unplugged, biased, shorted, open, or contaminated
- Connector corrosion, coolant intrusion, loose terminals, or damaged harness
- Low coolant, trapped air, thermostat fault, cooling fan fault, or real overheating for ECT-related codes
- Intake heat soak, damaged MAF/IAT assembly, or intake duct issue for IAT-related codes
- Reference voltage, ground, or PCM input issue after sensor and wiring checks
Symptoms
- Hard start
- Poor fuel economy
- Cooling fan runs unexpectedly
- Temperature gauge abnormal
- Rich or lean drivability symptoms
Diagnostic Steps
- Compare sensor readings to ambient temperature before start-up and to actual engine condition when warm
- Inspect connector fit, terminal tension, corrosion, coolant intrusion, rub-through, and harness routing
- Check reference voltage, ground, and signal response when the reading is stuck high or low
- For ECT faults, verify coolant level, trapped air, thermostat operation, fan operation, and actual temperature
- For IAT faults, inspect the intake path, MAF/IAT assembly, and heat-soak conditions
- Verify repair with plausible cold-start readings, warm-up behavior, and no pending sensor codes
Repair Difficulty
Moderate
General difficulty estimate for the most common repair path.
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Next Steps
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