P1112
VWIntake Air Temperature (IAT) Sensor Circuit Intermittent Low Voltage
Medium SeverityThe Intake Air Temperature (IAT) sensor measures the temperature of the air entering the engine. An intermittent low voltage reading from this sensor indicates a potential issue with its circuit or the sensor itself, which can lead to incorrect fuel mixture adjustments by the engine control unit and affect fuel efficiency or engine performance.
⚠️ Before You Begin (Safety First)
Always wear appropriate safety gear, such as gloves and eye protection. Ensure the vehicle is turned off and the battery is disconnected before performing any work to prevent electrical shock or accidental starting.
Common Symptoms
- Check Engine Light illuminated
- Reduced fuel economy
- Rough idle or poor engine performance
- Hesitation during acceleration
- Difficulty starting (especially in extreme temperatures)
Common Causes
- Faulty Intake Air Temperature (IAT) sensor
- Corrosion or damage to the IAT sensor electrical connector
- Damaged or frayed wiring in the IAT sensor circuit
- Loose or poor connection at the IAT sensor or ECM
- Less commonly, a fault within the Engine Control Module (ECM)
Frequently reported on: Volkswagen Jetta 2000-2005, Volkswagen Golf 2000-2006, Volkswagen Passat 1998-2005, Volkswagen Beetle 2000-2005
Diagnostic Steps
- Locate the Intake Air Temperature (IAT) sensor. It is typically found in the air intake duct or manifold.
- Inspect the electrical connector for corrosion, bent pins, or loose connections. Clean any corrosion with electrical contact cleaner.
- Check the wiring harness leading to the IAT sensor for any visible damage, fraying, or pinches.
- If no visible issues are found, consider testing the IAT sensor's resistance using a multimeter at varying temperatures (check service manual for specific values).
- If the sensor tests faulty or if the code returns after inspections, replace the IAT sensor. Ensure the replacement part is compatible with your VW vehicle.
- Clear the P1112 code using an OBD-II scanner and test drive the vehicle to see if the code returns.
👨🔧 When to Call a Professional
If after inspecting the wiring and replacing the IAT sensor, the code P1112 persists, or if other complex drivability issues are present, it's time to consult a professional mechanic. This could indicate a deeper electrical issue or a problem with the Engine Control Module (ECM).
Commonly Asked Questions
What does an intermittent low voltage from the IAT sensor mean?
It means the sensor is sending a signal that is too low at times, suggesting the air entering the engine is colder than it actually is, or there's a problem with the sensor's electrical circuit.
Can I drive my VW with a P1112 code?
You can usually drive the car, but it's recommended to address the issue promptly as it can affect fuel economy, emissions, and engine performance.
Is the IAT sensor difficult to replace?
For most VW models, replacing the IAT sensor is a relatively simple DIY task, often requiring basic tools and a short amount of time.
How do I test the IAT sensor?
You can test the IAT sensor by measuring its resistance across its terminals using a multimeter. The resistance should change predictably with temperature according to your vehicle's service manual specifications.
What if replacing the IAT sensor doesn't fix P1112?
If the code persists after sensor replacement, carefully re-inspect the wiring harness and connectors for damage. It might also indicate a problem with the Engine Control Module (ECM), which would require professional diagnosis.