P0112 - Intake Air Temperature Sensor 1 Circuit Low Input (Bank 1)
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System
Powertrain (Engine & Gearbox)
Related Fault Codes
Technical Description
P0112 is set when the Engine Control Module (ECM) detects a voltage from the Intake Air Temperature (IAT) sensor that is lower than the expected range (typically below 0.2V). The IAT sensor is an NTC thermistor where resistance decreases as temperature increases. A 'Low Input' condition (low voltage) is interpreted by the ECM as an extremely high intake air temperature (often exceeding 120°C/250°F). This is usually caused by a short to ground in the signal circuit or an internal short in the sensor. The ECM may use a default value for air temperature calculations, affecting ignition timing and fuel injection duration.
Possible Causes
Faulty IAT sensor (internal short)
Short to ground in the IAT signal circuit wiring
Damaged or corroded connector at the sensor
Faulty Engine Control Module (ECM)
Symptoms
Recommended Solution
- Visual Inspection: Check wiring and connector at the IAT sensor for chafing, exposed wires, or corrosion.
- Live Data Check: Use a scan tool to monitor IAT temperature. If it reads +120°C to +150°C on a cold engine, unplug the sensor. If the reading drops to -40°C, the sensor is faulty. If it remains high, there is a short in the wiring.
- Multimeter Testing: Check for 5V reference voltage at the connector with ignition on. Measure sensor resistance (typically 2k-3k Ohms at 20°C/68°F).
- Action: Clean connectors or replace the IAT sensor (often part of the Mass Air Flow sensor).
- Completion: Clear codes and perform a drive cycle.
Mechanic's Tip
Before replacing expensive components, always double-check wiring and connections. 80% of all sensor faults are actually due to corroded contacts or broken wires.
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