P1112
BMWIntake Air Temperature (IAT) Sensor Circuit Intermittent Low Voltage
Medium SeverityThe Intake Air Temperature (IAT) Sensor is sending an inconsistent signal to the engine's computer, indicating a momentary low voltage condition. This intermittent faulty reading can lead to the Engine Control Unit (ECU) miscalculating the necessary fuel mixture and ignition timing, potentially impacting engine performance and fuel efficiency.
⚠️ Before You Begin (Safety First)
Always ensure the engine is off and cool before working on any components. Disconnect the negative battery terminal before inspecting or replacing electrical sensors to prevent electrical shock or damage to the vehicle's electrical system. Be careful when working around hot engine parts and moving components.
Common Symptoms
- Check Engine Light illuminated
- Rough idle
- Reduced engine performance or power
- Decreased fuel economy
- Hesitation or stalling during acceleration
- Engine running rich or lean
Common Causes
- Faulty or failing Intake Air Temperature (IAT) Sensor
- Damaged, corroded, or loose wiring in the IAT sensor circuit
- Poor electrical connection at the IAT sensor connector
- Contamination or debris on the IAT sensor element
- Less commonly, a fault within the Engine Control Unit (ECU)
Frequently reported on: BMW 3 Series (E46, E90) 2000-2011, BMW 5 Series (E39, E60) 1997-2010, BMW X5 (E53, E70) 2000-2013, BMW Z4 (E85) 2003-2008
Diagnostic Steps
- Locate the Intake Air Temperature (IAT) sensor. It is typically found in the intake manifold or air intake tube after the air filter.
- Carefully inspect the electrical connector for the IAT sensor. Look for any signs of corrosion, bent pins, or loose connections. Ensure it is securely plugged in.
- Examine the wiring harness leading to the IAT sensor for any visible damage, frayed wires, or signs of rodent chewing. Repair any damaged wiring.
- Disconnect the sensor and use an electrical contact cleaner to clean both the sensor pins and the connector terminals. Allow to dry thoroughly before reconnecting.
- If possible, test the resistance of the IAT sensor using a multimeter at different temperatures (if you have a way to safely heat or cool it). Compare readings to factory specifications. An intermittent low voltage suggests an internal fault in the sensor.
- If inspection and cleaning do not resolve the issue, replace the IAT sensor with a new, OEM-quality part. This is generally a straightforward swap.
- Clear the P1112 code from the vehicle's ECU 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 sensor wiring and connector, and possibly replacing the Intake Air Temperature Sensor, the P1112 code persists or the engine exhibits significant performance issues, it's advisable to consult a professional BMW technician. Intermittent electrical issues can be challenging to diagnose without specialized tools and expertise.
Commonly Asked Questions
What does BMW P1112 specifically mean?
P1112 on a BMW indicates an intermittent low voltage reading from the Intake Air Temperature (IAT) sensor circuit. This means the engine's computer is intermittently receiving a signal from the IAT sensor that is lower than expected.
Can I drive my BMW with a P1112 code?
While you can typically drive with a P1112 code, it's not recommended for extended periods. The intermittent incorrect air temperature data can cause sub-optimal fuel mixture, leading to reduced fuel economy, decreased engine performance, and potentially long-term engine issues if left unaddressed.
How do I test the Intake Air Temperature sensor?
You can test the IAT sensor using a multimeter to measure its resistance. Disconnect the sensor and check the resistance across its terminals. The resistance should change predictably with temperature. Consult your vehicle's service manual for specific resistance values at various temperatures for your BMW model.
Where is the IAT sensor located on a BMW?
On most BMW models, the Intake Air Temperature (IAT) sensor is integrated into the Mass Air Flow (MAF) sensor or located within the air intake tube or manifold, positioned after the air filter but before the throttle body. Its exact location can vary by engine type and model.
What tools are needed to fix a P1112 code?
To diagnose and potentially fix a P1112 code, you will typically need an OBD-II scanner to read and clear codes, a multimeter for testing the sensor, basic hand tools (like screwdrivers or sockets, depending on sensor mounting), and possibly electrical contact cleaner.