P1112
GMIntake Air Temperature (IAT) Sensor Circuit Intermittent Low Voltage
Medium SeverityThe Intake Air Temperature (IAT) sensor measures the temperature of the air entering the engine, which is crucial for the engine control module (ECM) to calculate proper fuel delivery and ignition timing. An intermittent low voltage signal from this sensor circuit means the ECM is receiving readings that are sporadically too low, potentially causing incorrect fuel mixtures and impacting engine performance.
⚠️ Before You Begin (Safety First)
Always allow the engine to cool before working on it to prevent burns. Disconnect the negative battery terminal before performing any electrical work to avoid accidental shorts or shocks. Use appropriate personal protective equipment, such as gloves and eye protection.
Common Symptoms
- Check Engine Light illuminated
- Rough idle
- Reduced fuel economy
- Decreased engine performance
- Hesitation or stumbling during acceleration
- Black smoke from the exhaust (due to rich mixture)
Common Causes
- Faulty Intake Air Temperature (IAT) sensor
- Corroded or loose electrical connections at the IAT sensor or engine harness
- Damaged, frayed, or shorted wiring in the IAT sensor circuit
- Open circuit in the IAT sensor signal or ground wire
- Contaminated IAT sensor (e.g., oil or debris affecting readings)
- Less commonly, a faulty Engine Control Module (ECM)
Frequently reported on: Chevrolet Silverado 2000-2006, GMC Sierra 2000-2006, Chevrolet Tahoe 2000-2006, Pontiac Grand Prix 1997-2003, Cadillac Escalade 2002-2006
Diagnostic Steps
- Locate the Intake Air Temperature (IAT) sensor, typically found in the intake manifold or air intake tube.
- Carefully disconnect the electrical connector from the IAT sensor.
- Inspect the sensor and its electrical connector for any signs of corrosion, bent pins, or damage.
- Using a multimeter, check the resistance of the IAT sensor (consult a repair manual for expected values).
- Test the voltage at the IAT sensor connector to ensure the reference voltage and ground are present (typically 5V reference).
- If the sensor tests faulty or connections are corroded, replace the IAT sensor with a new one.
- Reconnect the electrical connector securely and clear the P1112 code using an OBD-II scanner.
- Drive the vehicle to see if the code returns and monitor engine performance.
👨🔧 When to Call a Professional
If after inspecting or replacing the Intake Air Temperature sensor the code persists or if there are other complex drivability issues, it is best to consult a professional mechanic. This indicates a potential underlying wiring harness problem, ECM issue, or a more intricate intermittent fault that requires specialized diagnostic tools and expertise.
Commonly Asked Questions
What is an Intake Air Temperature (IAT) sensor?
The IAT sensor measures the temperature of the air entering your engine, providing this data to the engine's computer (ECM) to optimize fuel delivery and ignition timing.
Can I drive with a P1112 code?
While you can usually drive with a P1112 code, it's not recommended for long periods as it can lead to reduced fuel economy, poor engine performance, and potentially richer fuel mixtures that can harm catalytic converters over time.
How can I confirm the IAT sensor is faulty?
You can test the IAT sensor's resistance using a multimeter and compare it to manufacturer specifications. Also, visually inspect the sensor and its wiring for any obvious damage or corrosion.
Is P1112 an expensive repair?
Replacing the IAT sensor itself is typically an inexpensive repair, as the sensor is relatively cheap and easy to access. However, if the issue is with the wiring harness or ECM, costs could increase.
Will cleaning the IAT sensor fix the P1112 code?
Sometimes, if the sensor is merely dirty or contaminated, carefully cleaning it with an electrical contact cleaner might resolve the issue. However, if the internal sensor element is faulty, replacement is necessary.