P1118: Manifold Air Temp Sensor Out of Range Low
The P1118 code indicates that the Engine Control Module (ECM) has detected a signal from the Manifold Air Temperature (MAT) sensor that is below the expected range, typically less than -40°F or -40°C. This sensor measures the temperature of the air entering the intake manifold, and a low reading can cause the ECM to enrich the fuel mixture, leading to poor fuel economy and drivability issues. Common causes include a faulty sensor, wiring issues, or a short to ground.
1. Symptoms You Will Notice
- Check Engine Light illuminated
- Poor fuel economy
- Rough idle or hesitation
- Black smoke from exhaust (rich mixture)
- Hard starting in cold weather
2. Most Common Causes
- Faulty Manifold Air Temperature sensor
- Short to ground in sensor circuit
- Open or damaged wiring/connector
- Corrosion at sensor connector
- ECM failure (rare)
3. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Visually inspect MAT sensor connector and wiring for damage or corrosion.
Step 3: Measure sensor resistance; compare to specifications (typically 2-10 kΩ at room temperature).
Step 4: Check for short to ground by disconnecting sensor and measuring voltage at harness (should be ~5V reference).
Step 5: If wiring and voltage are OK, replace the MAT sensor.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is generally safe for short trips, but prolonged driving can cause poor fuel economy, increased emissions, and potential damage to the catalytic converter due to a rich mixture. It's best to diagnose and repair promptly.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150, including parts (sensor $20-$50) and labor (0.5-1 hour at shop rates). DIY replacement is simple and can save labor costs.
5. Commonly Affected Makes
This is a manufacturer-specific code. The exact manufacturer is not confirmed in our current database.