P1119
HyundaiManifold Absolute Temperature Circuit High Input
Medium SeverityThe ECM (Engine Control Module) has detected a voltage signal from the Manifold Absolute Temperature (MAT) sensor that is unexpectedly high. This indicates to the ECM that the intake air temperature is extremely cold, which can lead to the ECM commanding an incorrect fuel mixture strategy.
⚠️ Before You Begin (Safety First)
Always disconnect the negative battery terminal before working on electrical components. Allow the engine to cool completely to avoid burns. Exercise caution when probing electrical circuits to prevent shorts or damage to the ECM.
Common Symptoms
- Check Engine Light illuminated
- Rough idle or poor engine performance, particularly during cold starts
- Decreased fuel economy
- Potential for rich or lean running conditions due to inaccurate air density calculations by the ECM
- Difficulty starting the engine in very cold weather
Common Causes
- Faulty Manifold Absolute Temperature (MAT) sensor
- Open circuit or high resistance in the MAT sensor signal wire
- Short to voltage in the MAT sensor signal circuit
- Corroded or loose electrical connectors at the MAT sensor or ECM
- Rarely, an internal fault within the Engine Control Module (ECM)
Frequently reported on: Hyundai Elantra (2007-2016), Hyundai Sonata (2006-2010), Hyundai Santa Fe (2007-2012), Hyundai Tucson (2005-2009), Hyundai Accent (2006-2011)
Diagnostic Steps
- Locate the Manifold Absolute Temperature (MAT) sensor. This sensor is typically found in the intake manifold or the air intake tube.
- Visually inspect the MAT sensor wiring harness and connector for any signs of damage, corrosion, or looseness. Repair as necessary.
- With the ignition off, disconnect the MAT sensor electrical connector.
- Using a multimeter, test the resistance of the MAT sensor across its terminals. Compare the reading to the manufacturer's specifications for various temperatures. A very high or infinite resistance reading often indicates an internal sensor fault.
- Verify the voltage supply to the sensor connector and check for continuity of the signal wire back to the ECM. A 'high input' suggests the signal wire might be open or shorted to a voltage source.
- If the sensor tests faulty or the wiring is confirmed good, replace the MAT sensor with a new, OE-quality part.
- Clear the P1119 diagnostic trouble code using an OBD-II scanner and perform a drive cycle to confirm the repair.
👨🔧 When to Call a Professional
If initial inspection and sensor replacement do not resolve the P1119 code, or if you suspect intermittent wiring issues or ECM involvement, it is advisable to consult with a professional diagnostic technician. They can perform advanced circuit testing and evaluate ECM rationality parameters.
Commonly Asked Questions
How does the ECM use the MAT sensor signal?
The ECM utilizes the MAT sensor signal to determine the density of the intake air. This data is critical for calculating the precise amount of fuel required for optimal combustion and maintaining proper air-fuel ratios.
Can a P1119 code impact my vehicle's emissions test?
Yes, an inaccurate MAT sensor signal can lead to incorrect fuel trim adjustments, potentially causing the engine to run too rich or too lean. This directly affects exhaust emissions and could cause your vehicle to fail an emissions inspection.
What is the typical voltage range for a properly functioning MAT sensor circuit?
While specific voltage ranges vary by manufacturer and temperature, a 'high input' typically means the ECM is seeing a voltage signal near the reference voltage (e.g., 5 volts) when it should be lower, indicating an open circuit or very low temperature.
Is it possible for the ECM itself to cause a P1119 code?
It is less common, but an internal ECM fault or a degraded driver circuit for the MAT sensor could theoretically cause a P1119. This would typically be diagnosed after ruling out the sensor and wiring integrity.
Will this code prevent my car from starting?
While a P1119 code might cause rough starting, especially in extreme temperatures, it's unlikely to completely prevent your car from starting unless the engine's fueling strategy is severely compromised.