P0112 on the 6.7L Cummins is an intake air temperature (IAT) sensor 1 circuit low input fault. The IAT sensor measures the temperature of air entering the engine so the ECM can fine-tune fueling, timing, and grid heater operation on this platform. When the ECM reads an IAT voltage that is too low, corresponding to an implausibly hot air temperature, it stores P0112.
Intake air temperature is one of the inputs the 6.7L uses to decide how long the intake grid heater stays energized during a cold start, so a false reading can affect cold-start quality as well as fueling. Because the sensor is a simple thermistor, P0112 usually traces to a short in the wiring or a failed sensor rather than anything internal to the engine, which makes it a quick fix once the circuit is checked.
What P0112 means
The IAT sensor is a thermistor whose resistance falls as temperature rises. Low resistance produces low signal voltage, which the ECM reads as very hot air. P0112 sets when the voltage stays at the low end of the scale, pointing to a short to ground in the signal wire, a sensor that has failed shorted, or a signal-to-ground bridge in the connector.
Common causes
- Signal wire shorted to ground
- Failed IAT sensor reading shorted
- Corroded connector bridging signal and ground
- Chafed harness rubbing through insulation
- Water intrusion in the sensor connector
Symptoms
- Check engine light, often with little drivability change
- Slightly altered fueling or timing
- Possible effect on grid heater cold-start strategy
- Minor smoke or rough running on a cold start
- Companion intake temperature or grid heater codes
How to diagnose it
View live IAT data with a scan tool. A reading pinned at an extreme hot value, well above ambient, confirms the low circuit fault. Inspect the sensor connector for corrosion, water, and bent pins. Back-probe the connector: unplugging the sensor should drive the reading to the opposite extreme if the wiring is intact, which helps separate a shorted sensor from a shorted wire. Check the signal wire for a short to ground and confirm continuity back to the ECM. Measure the sensor resistance against a temperature chart if in doubt.
How to fix it
Repair a signal wire shorted to ground and clean or replace a corroded connector, which resolves many P0112 cases. If the wiring is good but the sensor reads shorted, replace the IAT sensor. Confirm the sensor and connector are sealed against water to prevent a repeat. After the repair, clear the code, verify the IAT reading matches ambient temperature at a cold start, and road test. For the correct IAT sensor or connector for your 6.7L Cummins, contact sales@coredieselparts.com.
Frequently asked questions
Is P0112 serious on a 6.7L Cummins?
Drivability is usually only mildly affected, but incorrect air temperature data can skew fueling and grid heater timing. Fix it to keep cold starts and emissions strategy accurate.
Can a shorted wire cause P0112?
Yes. A signal wire shorted to ground reads as impossibly hot air and sets the low circuit code. Inspect the harness for chafing before replacing the sensor.
How do I tell the sensor from the wiring?
Unplug the sensor and watch the reading. If it swings to the opposite extreme, the wiring is intact and the sensor is likely shorted. If it stays low, suspect a wire shorted to ground.
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