P0110

What the Code Means

P0110 flags a fault in the intake air temperature sensor circuit (Intake Air Temperature Sensor, Bank 1). The IAT sensor measures the temperature of the air entering the intake manifold and sends that data to the DME.

The DME uses IAT readings to calculate air density and trim the air-fuel mixture. The code sets when voltage in the sensor circuit falls outside the factory range — the DME stops getting reliable data and the mixture is no longer optimal.

Typical causes: a failed sensor, damaged wiring, an open circuit, or a corroded connector. On BMW, the IAT sensor is often built into the MAF sensor or mounted in the intake manifold — the layout determines how much work the repair takes.

Symptoms

• Check Engine Light;
• rough running;
• reduced power;
• poor combustion;
• increased fuel consumption;
• hard cold starts in cold weather;
• incorrect temperature readings on the instrument cluster (where applicable).

Diagnosis and Repair

Step 1. Inspect the Wiring and Connector

Check the IAT sensor wiring for opens, chafing, and corrosion. Clean the sensor connector and make sure the pins are seated firmly.

Step 2. Test the Sensor

Run an ohm test: measure sensor resistance at different temperatures and compare it to spec. A quick check is to compare the IAT reading against ambient air temperature — with a cold engine they should match.

Step 3. Check the Circuit

Check the power and ground circuits back to the DME — an open or high resistance in the circuit sets the same code as a failed sensor.

Step 4. Fix the Fault

• if sensor resistance is out of spec, replace the IAT sensor;
• on BMW where the IAT is built into the MAF sensor, replace the whole MAF sensor.

Step 5. Finish Up

Clear the DME and check whether the code returns. If the fault doesn't come back after the cause is fixed, the repair is good.

Secondary Problems

• increased fuel consumption from an incorrect air-fuel mixture;
• carbon buildup in the engine;
• catalytic converter damage if the fault is left in service for a long time.

The risk of serious consequences is minimal with a timely repair, but don't put off fixing the code.