MAZDA Code P1112: Causes, Symptoms, and Solutions
Meaning of Code P1112
Code P1112 on a Mazda indicates a problem with the Intake Air Temperature (IAT) sensor or its circuit. This sensor measures the temperature of the air entering the engine and sends a signal to the Engine Control Module (ECM).
- Operation: The IAT sensor uses a thermistor whose electrical resistance decreases as the temperature increases.
- Location: Integrated into the Mass Air Flow (MAF) sensor or mounted on the air filter housing.
- Impact: The ECM uses this data to adjust the air-fuel mixture, ignition timing, and other critical parameters.
Common Symptoms
- Check Engine Light illuminated (or warning message).
- Unstable idle or vibrations.
- Increased fuel consumption.
- Reduced performance (weak acceleration).
- Hard starting in cold weather.
Possible Causes
- Faulty IAT Sensor:
- Damaged or degraded thermistor.
- Cut or oxidized internal wiring.
- Electrical Problems:
- Short circuit or open circuit in the sensor harness.
- Corroded, loose, or poorly secured connectors.
- ECM Failure:
- Programming error or hardware failure (rare).
Diagnostic Procedures
- Visual Inspection:
- Locate the IAT sensor (near the air filter or integrated into the MAF).
- Check the harness and connectors for exposed wires, damaged insulation, or corrosion.
- IAT Sensor Test:
- Disconnect the connector and measure the resistance with a multimeter.
- Expected Values:
- ~2,000 to 3,000 Ω at 20°C.
- ~200 to 400 Ω at 80°C.
- Compare with Mazda specifications.
- Electrical Circuit Check:
- Test the supply voltage (5 V with ignition on).
- Check continuity between the sensor and the ECM.
Recommended Solutions
- Replace the Faulty IAT Sensor:
- Choose a compatible or OEM sensor (e.g., Denso, Hitachi).
- Clean the mounting area to prevent air leaks.
- Repair the Electrical Harness:
- Repair damaged wires with waterproof solder joints.
- Replace oxidized or broken connectors.
- Reset the ECM:
- Clear the P1112 code with an OBD-II scanner after repair.
- If the code persists, consider ECM reprogramming.
Important Precautions
- Disconnect the battery before any electrical work.
- Avoid contaminants: Clean the air filter housing to prevent incorrect readings.
- Test the MAF sensor: If the IAT sensor is integrated into the MAF, also check its condition.
Estimated Costs
- IAT Sensor: €30 to €100.
- Labor: 0.5 to 1 hour (€40 to €100).
- MAF Replacement (if integrated): €100 to €300.
Conclusion
Code P1112 on a Mazda often signals a simple problem like a dirty IAT sensor or a faulty connector. Ignoring this code can lead to an unbalanced air-fuel mixture, eventually damaging the catalytic converter or increasing engine wear. If basic checks do not resolve the issue, consult a certified Mazda mechanic for a thorough diagnosis, especially if symptoms like high fuel consumption persist.