P1118: Manifold Air Temp Sensor Out of Range Low
The P1118 code indicates that the Engine Control Module (ECM) has detected a voltage signal from the Manifold Air Temperature (MAT) sensor that is lower than the expected range, typically below 0.2 volts. This sensor measures the temperature of the air entering the intake manifold, and a low voltage reading corresponds to a high temperature reading (above 300°F or 150°C). The ECM uses this data to adjust fuel delivery and ignition timing. A faulty sensor, wiring issues, or a short to ground can cause this code.
01. Most Common Causes
- Faulty Manifold Air Temperature (MAT) sensor
- Short to ground in the sensor signal circuit
- Open or shorted wiring in the sensor harness
- Corroded or damaged connector at the sensor
- ECM internal failure (rare)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Poor fuel economy
- Rough idle or hesitation during acceleration
- Black smoke from exhaust (rich mixture)
- Engine may run poorly or stall
03. Step-by-Step Diagnosis
Step 1: Use an OBD2 scanner to confirm the code and check for other related codes.
Step 2: Visually inspect the MAT sensor and its wiring for damage, corrosion, or loose connections.
Step 3: Disconnect the sensor and measure its resistance with a multimeter; compare to manufacturer specs (typically 2-10 kΩ at room temperature).
Step 4: Check for a short to ground by measuring voltage at the sensor connector with the ignition on (should be around 5V reference).
Step 5: If sensor and wiring are okay, test the ECM by backprobing the signal wire and monitoring voltage while varying sensor temperature.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances with this code, as it can cause poor engine performance, reduced fuel economy, and potential damage to the catalytic converter due to incorrect air-fuel mixture.
How much does it cost to fix?▼
The cost to fix P1118 typically ranges from $50 to $150, including parts and labor. The sensor itself costs around $20-$50, and labor is about $30-$100 depending on the vehicle.