P1109
NissanNissan-specific code indicating an intermittent signal from the Intake Air Temperature (IAT) Sensor 'B' circuit.
Medium SeverityThis code means your vehicle's Engine Control Module (ECM) is receiving an inconsistent or unreliable signal from the Intake Air Temperature (IAT) Sensor 'B'. An intermittent signal can cause the ECM to miscalculate the air density entering the engine, leading to incorrect fuel mixture adjustments and affecting engine performance and fuel efficiency.
⚠️ Before You Begin (Safety First)
Always wear appropriate personal protective equipment (PPE) such as gloves and eye protection. Disconnect the negative battery terminal before performing any electrical work to prevent accidental shorts or injury. Allow the engine to cool sufficiently before working on components to avoid burns.
Common Symptoms
- Check Engine Light illumination
- Reduced fuel economy
- Rough idle or stalling
- Poor engine performance or hesitation during acceleration
- Difficulty starting the engine (less common)
Common Causes
- Faulty Intake Air Temperature (IAT) Sensor 'B'
- Loose or corroded electrical connections at the IAT sensor or harness
- Damaged or frayed wiring in the IAT sensor circuit
- Contamination on the IAT sensor element
- Engine Control Module (ECM) malfunction (rare)
Frequently reported on: Nissan Altima 2005-2010, Nissan Maxima 2004-2008, Nissan Frontier 2005-2012, Nissan Titan 2004-2015
Diagnostic Steps
- Locate the Intake Air Temperature (IAT) Sensor 'B'. Consult your vehicle's service manual for its exact location, as it can vary. It's often found in the intake manifold or air intake ducting.
- Visually inspect the IAT sensor and its electrical connector for any signs of damage, corrosion, or loose connections. Ensure the connector is securely seated.
- Carefully disconnect the IAT sensor's electrical connector. Use electrical contact cleaner to clean both the sensor terminals and the harness connector pins.
- Inspect the wiring leading to the IAT sensor for any visible breaks, chafing, or signs of damage. Repair any damaged wiring as necessary.
- If possible, test the resistance of the IAT sensor using a multimeter. Compare the readings to specifications found in your vehicle's service manual. Resistance should change predictably with temperature.
- If visual inspection and cleaning do not resolve the issue, and the sensor tests faulty, replace the IAT sensor with a new, OEM-quality part.
- Clear the P1109 code using an OBD-II scanner and test drive the vehicle to confirm the repair.
👨🔧 When to Call a Professional
If the P1109 code persists after checking and cleaning connections, or if diagnostic tools reveal erratic voltage readings that don't seem related to simple connection issues, consult a professional technician. Intermittent electrical faults can be challenging to diagnose without specialized equipment.
Commonly Asked Questions
What does 'IAT - B Sensor' mean?
In Nissan vehicles, 'IAT - B Sensor' typically refers to a secondary Intake Air Temperature sensor, or a specific circuit related to the IAT sensor that the manufacturer has designated as 'B'. Some engines might have multiple IAT sensors.
Can I drive my Nissan with a P1109 code?
While you can generally drive with this code, it's not advisable to do so for an extended period. The intermittent signal can lead to reduced fuel economy, poor engine performance, and potentially increase emissions. It's best to address it promptly to avoid further issues.
How can I test the IAT sensor myself?
You can test an IAT sensor using a multimeter to measure its resistance. The resistance should change as the sensor's temperature changes (e.g., using a heat gun or ice water). You'll need to compare your readings to the specific resistance-to-temperature chart provided in your vehicle's service manual.
Is the P1109 code serious?
P1109 is a medium severity code. While it might not immediately strand your vehicle, an intermittent IAT sensor can lead to significant reductions in fuel efficiency and noticeable drivability problems. Prompt diagnosis and repair are recommended.
What's the most common cause for an intermittent IAT sensor signal?
The most common causes for an intermittent signal are loose or corroded electrical connections at the sensor or within the wiring harness. Sometimes the sensor itself can have an internal intermittent fault.