P1119
NissanP1119: Manifold Absolute Temperature (MAT) Sensor Circuit High Input. This code indicates that the Engine Control Module (ECM) has detected a voltage signal from the MAT sensor that is higher than the expected operating range.
Medium SeverityThis code means the Manifold Absolute Temperature (MAT) sensor is sending a signal that's too high for the engine computer. This typically happens when there's an electrical problem in the sensor or its wiring, which can affect the engine's air-fuel mixture calculations.
⚠️ Before You Begin (Safety First)
When working under the hood, always disconnect the battery's negative terminal to prevent accidental shorts or shocks. Allow the engine to cool down completely before touching any components. Wear appropriate eye protection and gloves. Be careful with hot engine parts and electrical connections.
Common Symptoms
- Check Engine Light illumination
- Rough idle
- Reduced engine performance
- Poor fuel economy
- Difficulty starting, especially in cold weather
- Engine hesitation
Common Causes
- Faulty Manifold Absolute Temperature (MAT) sensor
- Open circuit in the MAT sensor signal wire
- Short circuit to voltage in the MAT sensor circuit
- Corroded or loose electrical connectors at the MAT sensor or ECM
- Faulty Engine Control Module (ECM), though this is less common
Frequently reported on: Nissan Altima 2007-2012, Nissan Maxima 2004-2008, Nissan Sentra 2007-2012, Nissan Pathfinder 2005-2012
Diagnostic Steps
- First, you'll want to visually inspect the Manifold Absolute Temperature (MAT) sensor and its wiring harness. Look for any obvious signs of damage, such as frayed wires, corrosion on the connector, or a sensor that looks physically broken.
- Next, you'll need to locate the MAT sensor. It's usually found in the intake manifold or the intake air ducting. Once you find it, gently disconnect the electrical connector.
- Now, get out your multimeter. You'll want to test the MAT sensor's resistance. The resistance should change with temperature; a high input code usually means infinite resistance (an open circuit) or a reading that's way out of specification. You can often find specific resistance values in your vehicle's service manual.
- After that, you'll need to check the wiring harness itself. With the ignition off and the MAT sensor disconnected, use your multimeter to check for continuity between the sensor connector and the ECM connector pins. Also, check for any shorts to ground or shorts to voltage.
- If the sensor tests bad or the wiring is damaged, you'll need to replace the MAT sensor or repair the wiring. Make sure to use the correct replacement part for your specific Nissan model. Once replaced, clear the code with an OBD-II scanner and test drive the vehicle to confirm the repair.
👨🔧 When to Call a Professional
If you've checked the basic connections and still can't diagnose the issue, or if you're not comfortable using a multimeter for electrical testing, it's best to consult a professional mechanic. They have specialized diagnostic tools to pinpoint complex electrical problems and can ensure the repair is done correctly, teaching you along the way.
Commonly Asked Questions
What exactly does 'high input' mean for the MAT circuit?
When the ECM sees a 'high input,' it means the voltage signal it's receiving from the Manifold Absolute Temperature sensor is above the expected maximum operating range. Think of it like a volume knob turned all the way up, but the system isn't expecting it to go that high. This often points to an open circuit or a sensor failure.
Can I drive with a P1119 code active?
While you might be able to drive your Nissan with this code, it's not recommended for long. The engine's computer relies on accurate temperature readings to adjust the air-fuel mixture. Without it, your engine might run too rich or too lean, leading to poor performance, reduced fuel economy, and potentially causing long-term damage to components like the catalytic converter. It's best to address it as soon as you can.
Is the Manifold Absolute Temperature sensor the same as the Intake Air Temperature (IAT) sensor?
That's a great question! For many vehicles, yes, they are essentially the same thing or perform a very similar function. The MAT sensor specifically measures the temperature of the air entering the engine's intake manifold, which is crucial for the ECM to calculate air density and inject the right amount of fuel. Some manufacturers just use different terminology, or combine it into a MAF sensor.
How do I test the MAT sensor with a multimeter?
To test it, first disconnect the sensor. Set your multimeter to measure resistance (Ohms). Connect the probes to the two terminals of the sensor. You should get a resistance reading. You'll then compare this reading to the specifications in your vehicle's service manual, which usually provides a resistance vs. temperature chart. As the sensor gets warmer or colder, the resistance value should change accordingly. A 'high input' code often means you'll see a very high, or infinite, resistance reading.
If I replace the MAT sensor, do I need to clear the code?
Yes, absolutely! After replacing the sensor, you'll need to use an OBD-II scanner to clear the P1119 code from the ECM's memory. Even if the problem is fixed, the light won't turn off on its own immediately. Clearing the code also allows the ECM to re-learn optimal operating parameters with the new sensor. Make sure to take a test drive afterward to confirm the repair and ensure the code doesn't return.