P1119
SubaruManifold Absolute Temperature Circuit High Input
Medium SeverityThis code, P1119, means your Subaru's computer, the ECM, is seeing an unexpectedly high voltage signal from the Manifold Absolute Temperature (MAT) sensor. What that high voltage typically tells the computer is that the intake air temperature is extremely cold, or more commonly, it indicates an open circuit in the sensor or its wiring, meaning the signal isn't making it back to the ECM correctly.
⚠️ Before You Begin (Safety First)
Always ensure your vehicle is on a level surface, the engine is off and cool, and the parking brake is engaged before working. When dealing with electrical components, disconnect the negative battery terminal to prevent accidental shorts or damage to sensitive electronics. Wear appropriate eye protection and gloves. Be cautious around hot engine components and rotating parts if the engine must be running for testing.
Common Symptoms
- Check Engine Light (CEL) illuminated on the dashboard
- Reduced fuel economy due to incorrect fuel trim adjustments
- Rough idle or stalling, especially when the engine is cold
- Difficulty starting, particularly in varying temperatures
- Poor engine performance or lack of power as the ECM struggles with air density calculations
Common Causes
- A faulty Manifold Absolute Temperature (MAT) sensor itself, which is internally open or shorted, causing an incorrect high voltage reading
- An open circuit in the MAT sensor's wiring, meaning a broken wire preventing the signal from reaching the ECM
- A poor electrical connection at the MAT sensor connector, leading to intermittent or complete signal loss
- Corrosion or damage to the MAT sensor's terminals or the wiring harness connector
- Less commonly, a fault within the Engine Control Module (ECM), though this is usually diagnosed after ruling out sensor and wiring issues
Frequently reported on: 2008-2014 Subaru Impreza, 2005-2015 Subaru Forester, 2006-2012 Subaru Legacy, 2005-2014 Subaru Outback, 2008-2014 Subaru WRX
Diagnostic Steps
- Access the MAT Sensor: Locate the Manifold Absolute Temperature sensor. On many Subarus, this sensor might be integrated into the Mass Air Flow (MAF) sensor assembly, which is usually found right after the air filter box in the intake tube. If it's a standalone sensor, it will be in the intake manifold.
- Visual Inspection: Disconnect the electrical connector from the sensor. Carefully inspect the sensor's connector and the wiring harness for any signs of corrosion, bent pins, or damaged wires. Look for any frayed insulation or signs of rodent damage.
- Check Wiring for Open Circuit: Using a multimeter, check for continuity in the sensor's signal wire from the sensor connector back to the ECM connector. A 'high input' often means an open circuit, so you're looking for where the connection breaks.
- Test MAT Sensor Resistance: If the sensor is accessible and separate, you can test its internal resistance. At room temperature, consult your Subaru's service manual for the specified resistance values. A completely open circuit (infinite resistance) or a wildly out-of-spec reading indicates a faulty sensor.
- Check Reference Voltage: With the ignition on (engine off), use your multimeter to check for the 5-volt reference signal at the sensor harness connector. If this reference voltage is missing, the problem might be further up the circuit or even at the ECM.
- Clear the Code: After making any repairs, use an OBD-II scanner to clear the P1119 code. Then, take the vehicle for a test drive to ensure the code does not return.
👨🔧 When to Call a Professional
If you've checked the basic connections and still can't identify the fault, or if you're not comfortable using a multimeter for electrical diagnosis, it's best to take your Subaru to a qualified mechanic or dealership. Complex wiring issues or ECM-related problems require specialized tools and expertise.
Commonly Asked Questions
What exactly does 'high input' mean for a sensor circuit?
In simple terms, a 'high input' usually means the voltage signal the computer is receiving from the sensor is at or near its maximum possible voltage, or that the circuit is open. For a temperature sensor, a very high voltage typically corresponds to a very cold temperature reading, but often it signals a broken wire or a completely failed sensor circuit.
Can I still drive my Subaru with a P1119 code?
While it's unlikely to cause immediate catastrophic failure, driving with P1119 is not recommended for an extended period. Your engine's fuel delivery and timing will be compromised, leading to reduced fuel economy, increased emissions, and potential rough running or stalling. It's best to address it as soon as possible to avoid further issues.
Is the MAT sensor always separate from the MAF sensor on a Subaru?
Not always. On many modern Subarus, the Manifold Absolute Temperature (MAT) sensor is actually integrated into the Mass Air Flow (MAF) sensor assembly. This means if you need to replace the MAT sensor, you might actually be replacing the entire MAF unit. Always consult your specific vehicle's service manual or parts diagram.
How do I know if the problem is the sensor or the wiring?
That's a great question, and it's where diagnosis comes in! You'd typically use a multimeter to test the resistance of the sensor itself (if standalone) and then test for continuity and voltage signals along the wiring harness. If the sensor tests good but the wiring has an open circuit or no reference voltage, you know to focus on the harness.
Will cleaning my MAF sensor fix a P1119 code?
If your MAT sensor is integrated into your MAF sensor, then yes, cleaning the MAF sensor with a specialized MAF cleaner can sometimes resolve issues if the temperature sensing element was simply dirty. However, if there's an actual electrical fault or open circuit, cleaning alone won't fix it. It's a good first step, but follow up with electrical tests if the code persists.