P0112 is a generic OBD-II powertrain code indicating an Intake Air Temperature (IAT) Sensor 1 Circuit Low Input condition. The powertrain control module detects a voltage signal from the IAT sensor that falls below the minimum expected threshold.
Because this code identifies an electrical circuit fault, it does not automatically prove the IAT sensor itself has failed. Accurate diagnosis requires testing the sensor resistance and the signal and ground circuits to isolate the root cause.
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Key Takeaways
- P0112 indicates a low voltage condition or short to ground in the signal circuit for the primary Intake Air Temperature (IAT) sensor.
- Possible causes include damaged wiring, corroded connectors, an internally shorted IAT sensor, or a failed PCM driver.
- Symptoms typically include an illuminated Check Engine Light, poor fuel economy, and incorrect transmission shift points.
- Diagnosis involves comparing live sensor data to ambient temperatures, inspecting the harness, and testing the sensor resistance with a multimeter.
- Repairs require fixing the confirmed electrical fault, which may involve wiring repairs or replacing the IAT sensor.
P0112 Code Description and Implications
P0112 is a generic diagnostic trouble code that applies to all OBD-II equipped vehicles. It indicates that the powertrain control module (PCM) has detected a low voltage condition in the circuit for Intake Air Temperature (IAT) Sensor 1.
Most IAT sensors are negative temperature coefficient (NTC) thermistors. As intake air temperature increases, sensor resistance decreases, and the signal voltage drops.
When the PCM reads a signal voltage near zero, it interprets this as an extremely high temperature or a short to ground. This code strictly monitors the electrical circuit, not the actual mechanical temperature of the intake air.
Common Causes of the P0112 Code
Possible causes for a circuit low condition include a short to ground in the IAT sensor signal wire, often caused by chafed insulation rubbing against the engine block or chassis.
Damaged, corroded, or loose electrical connectors at the sensor harness or mass airflow sensor housing can also interrupt the circuit or cause a short.
An internal electrical failure of the IAT sensor, causing it to short internally and drop resistance to near zero, is another possibility.
In rare cases, a failed reference voltage or ground circuit inside the powertrain control module may cause this code.
Symptoms Associated With P0112
Because the PCM relies on the IAT sensor for fuel trim calculations and transmission shift scheduling, a low voltage fault will trigger fail-safe strategies.
The most common symptom is an illuminated Check Engine Light. The PCM may also default to a predetermined temperature value, leading to poor fuel economy and harsh transmission shifts.
Other symptoms include rough idling, hesitation during acceleration, and an inaccurate intake air temperature reading on a scan tool or driver information center.
Diagnosing the P0112 Trouble Code
Diagnosis begins by using a scan tool to view the live data for the IAT sensor. Compare the displayed intake air temperature to the ambient air temperature or engine coolant temperature on a cold, soaked engine.
If the IAT reading shows an implausibly high temperature, the circuit is shorted.
Visually inspect the wiring harness and connector at the IAT sensor for physical damage, corrosion, or loose pins.
Use a digital multimeter to measure the electrical resistance across the sensor terminals and compare it to the manufacturer specifications. Check the signal circuit for a short to ground.
Repairing the P0112 Issue
If testing confirms damaged wiring or a short to ground in the harness, repair or replace the affected wiring sections and secure the harness away from hot or sharp components.
If the IAT sensor fails the electrical resistance test or shows an internal short, replace the sensor with a component meeting the correct vehicle specification.
If the IAT sensor is integrated into the mass airflow (MAF) sensor housing, the entire MAF sensor assembly may need to be replaced.
After completing the electrical repair, clear the diagnostic trouble codes and verify the live data reads correctly as the engine operates.
Cost Considerations for P0112 Repairs
Repair costs depend heavily on diagnostic time, component accessibility, and whether the IAT sensor is a standalone component or integrated into the mass airflow sensor.
Wiring repairs are generally less expensive but require precise diagnostic time to locate the exact point of the short circuit.
Replacing a standalone IAT sensor involves standard parts costs and minimal labor, while replacing an integrated MAF/IAT assembly involves higher parts costs.
Prevention Strategies for Future Occurrences
Inspect exposed engine wiring harnesses near the air intake tube and sensor connectors for signs of heat damage, chafing against engine components, or rodent activity.
Ensure that the electrical connector at the sensor remains clean and properly sealed to prevent moisture intrusion and corrosion in the circuit.
Troubleshooting Tips and Best Practices
Do not assume a P0112 code means the engine is actually overheating or ingesting extremely hot air. This code specifically flags an electrical low voltage or short to ground condition, which the PCM interprets as a high temperature.
Do not ignore a faulty IAT sensor reading. While the vehicle may remain drivable, the PCM will use a default fail-safe temperature value, which negatively impacts fuel efficiency and emissions over time.
Always verify whether your vehicle uses a standalone IAT sensor or one integrated into the mass airflow sensor before ordering replacement parts.
More OBD-II Codes
| P0111 | P0108 | P0107 | P0101 |
| P0100 | P0087 | P0113 | P0117 |
| P0118 | P0121 | P0122 | P0123 |
| P0130 | P0131 | P0132 | P0133 |
| P0171 | P0172 | P0174 | P0170 |
| P0135 | P0136 | P0140 | P0141 |
Frequently Asked Questions
Is P0112 a generic OBD-II code?
Yes. P0112 is a generic SAE code, meaning its definition as an Intake Air Temperature Sensor 1 Circuit Low Input fault applies universally across all OBD-II compliant vehicle makes and models.
Can I drive with a P0112 code?
Yes, you can generally drive the vehicle. However, the PCM will use a default fail-safe temperature value, which can lead to poor fuel economy, harsh transmission shifts, and increased emissions over time.
Will a P0112 code cause my engine to overheat?
No. P0112 indicates an electrical short to ground that the PCM interprets as extremely hot intake air. It does not reflect the actual engine coolant temperature or cause mechanical engine overheating.
Can a dirty air filter cause a P0112 code?
No. A dirty air filter restricts airflow but does not cause an electrical short to ground in the sensor circuit. P0112 specifically flags a wiring fault, connector issue, or internal sensor failure.
Does P0112 mean my intake air temperature sensor is bad?
Not necessarily. While a failed sensor is a possible cause, a short to ground in the wiring harness, a corroded connector, or a damaged ground wire will also cause the signal voltage to drop and trigger this code.
What Should You Do About the P0112 Code?
Confirm the exact factory definition for your vehicle, then follow the applicable manufacturer diagnostic procedure. Inspect the relevant system and components for electrical faults, and repair or replace the confirmed failed parts to restore proper operation.
