P1110
SubaruThe P1110 diagnostic trouble code for Subaru vehicles indicates an open circuit or short circuit condition detected in the Intake Air Temperature (IAT) sensor's D/C circuit by the Engine Control Unit (ECU).
Medium SeverityThis code signifies that the Intake Air Temperature (IAT) sensor is experiencing an electrical fault, either an open circuit or a short circuit. This electrical problem prevents the engine's computer from accurately reading the temperature of the air entering the engine, which can lead to incorrect fuel mixture adjustments and potentially affect engine performance and fuel economy.
⚠️ Before You Begin (Safety First)
Always disconnect the battery before performing any electrical work on your vehicle to prevent accidental short circuits or injury. Allow the engine to cool completely before handling any components under the hood. Wear appropriate personal protective equipment, including safety glasses and gloves, to protect against hot surfaces and sharp edges.
Common Symptoms
- Illuminated Check Engine Light
- Decreased fuel economy
- Rough idle or hesitation during acceleration
- Engine running rich or lean
- Potential failed emissions test
Common Causes
- Faulty or failed Intake Air Temperature (IAT) sensor
- Damaged or corroded wiring in the IAT sensor circuit
- Loose or corroded electrical connector to the IAT sensor
- Short circuit within the IAT sensor or its wiring
- Open circuit within the IAT sensor or its wiring
- Engine Control Unit (ECU) malfunction (rare)
Frequently reported on: Subaru Forester (2000-2005), Subaru Impreza (1998-2004), Subaru Legacy (1999-2005), Subaru Outback (2000-2005)
Diagnostic Steps
- Locate the Intake Air Temperature (IAT) sensor, typically found in the intake manifold or air intake tube.
- Visually inspect the IAT sensor's electrical connector and wiring for any signs of damage, corrosion, fraying, or loose connections.
- Carefully disconnect the electrical connector from the IAT sensor.
- Using a multimeter, test the resistance of the IAT sensor across its terminals. Compare the reading to your vehicle's service manual specifications (resistance should change with temperature).
- If the sensor's resistance is out of specification, replace the IAT sensor with a new, OEM-equivalent part.
- Reconnect the electrical connector securely and clear the P1110 code using an OBD-II scanner.
- Start the engine and check if the Check Engine Light returns.
👨🔧 When to Call a Professional
If, after replacing the IAT sensor and inspecting its wiring, the P1110 code persists, it is strongly recommended to consult a professional mechanic. Persistent electrical issues may indicate a more complex problem within the vehicle's wiring harness or potentially a fault with the Engine Control Unit (ECU), which requires advanced diagnostic tools and expertise.
Commonly Asked Questions
What is the Intake Air Temperature (IAT) sensor?
The IAT sensor measures the temperature of the air entering the engine. This information is used by the ECU to adjust the fuel mixture for optimal performance and emissions.
Can I drive my Subaru with a P1110 code?
While driving short distances may be possible, it is not recommended for an extended period. The engine's performance, fuel economy, and emissions will be negatively affected, and prolonged driving could potentially lead to other engine issues.
Where is the IAT sensor located on a Subaru?
The IAT sensor is typically located in the air intake tube, after the air filter and before the throttle body, or sometimes integrated into the MAF sensor. Consult your vehicle's service manual for the exact location.
How much does it cost to replace an IAT sensor?
The cost of an IAT sensor itself is relatively inexpensive, usually between $20-$50 for the part. If you do it yourself, that's the only cost. Professional installation might add $50-$150 in labor.
Do I need to clear the code after replacing the IAT sensor?
Yes, after replacing the sensor, you should clear the P1110 code using an OBD-II scanner. If the repair was successful, the code should not return.