P1112
NissanIntake Air Temperature (IAT) Sensor Circuit Intermittent Low Voltage
Medium SeverityThe Intake Air Temperature (IAT) sensor is sending an intermittently low voltage signal to the engine control unit (ECU), indicating that the intake air is colder than it actually is. This incorrect temperature reading can lead to improper fuel mixture adjustments, potentially causing rough idling, poor fuel economy, or a lack of power.
⚠️ Before You Begin (Safety First)
Always disconnect the battery before working on electrical components to prevent accidental shorts or injury. Allow the engine to cool down completely before handling engine bay parts to avoid burns. Use appropriate personal protective equipment, such as safety glasses and gloves.
Common Symptoms
- Check Engine Light illumination
- Rough idle or unstable engine RPM
- Reduced fuel efficiency
- Poor engine performance or hesitation during acceleration
- Difficulty starting the engine in some cases
Common Causes
- Faulty Intake Air Temperature (IAT) sensor
- Corroded, loose, or damaged electrical connector for the IAT sensor
- Damaged, frayed, or shorted wiring in the IAT sensor circuit
- Open circuit in the IAT sensor wiring
- Rarely, a faulty Engine Control Unit (ECU)
Frequently reported on: Nissan Altima (2002-2006), Nissan Frontier (2005-2019), Nissan 350Z (2003-2008), Nissan Sentra (2000-2006), Nissan Xterra (2000-2015)
Diagnostic Steps
- Locate the Intake Air Temperature (IAT) sensor, which is typically found in the intake manifold or the air intake tube after the air filter.
- Inspect the IAT sensor's electrical connector for any signs of corrosion, bent pins, looseness, or damage.
- Visually inspect the wiring leading to the IAT sensor for any signs of fraying, cuts, or heat damage.
- With the engine off and cool, disconnect the IAT sensor and test its resistance using a multimeter, comparing readings to your vehicle's service manual specifications at various temperatures.
- Using a multimeter, check for proper reference voltage (usually 5V) and a good ground at the IAT sensor's wiring harness connector.
- If the IAT sensor tests faulty or the connector/wiring is confirmed to be damaged, replace the IAT sensor or repair the wiring as necessary.
- Clear the P1112 code using an OBD-II scanner and perform a test drive to confirm the repair and ensure the code does not return.
👨🔧 When to Call a Professional
If the code reappears shortly after replacing the IAT sensor and inspecting the wiring, or if you suspect a deeper electrical issue with the wiring harness or ECU, it's best to consult a professional mechanic for advanced diagnostics.
Commonly Asked Questions
Can I drive with a P1112 code?
While you may be able to drive with this code, it's not recommended for extended periods. It can lead to decreased fuel economy, rough engine performance, and potentially damage other engine components over time due to improper fuel mixture.
What does the Intake Air Temperature (IAT) sensor do?
The IAT sensor measures the temperature of the air entering the engine. This information is crucial for the Engine Control Unit (ECU) to calculate the correct amount of fuel to inject for optimal combustion.
How much does an IAT sensor replacement cost?
The cost of a new IAT sensor itself typically ranges from $20 to $60, depending on your Nissan model and the brand of the part. Labor costs, if you have a mechanic do it, would be extra.
Is P1112 always caused by a bad IAT sensor?
Not always. While a faulty IAT sensor is the most common cause, the code can also be triggered by issues with the sensor's electrical connector, damaged wiring in the circuit (such as an open or short), or, in rare cases, a problem with the ECU itself.
How do I clear the P1112 code after fixing the issue?
After completing the repair, you will need to use an OBD-II scan tool to clear the P1112 code from your vehicle's ECU. Disconnecting the car battery for a short period can also sometimes clear codes, but it may reset other learned engine parameters.