P1118
FordManifold Absolute Temperature Circuit Low Input
Medium SeverityThis code means the Manifold Air Temperature (MAT) sensor circuit is sending a low voltage signal to the engine computer. This screws up fuel delivery, often causing the engine to run rough or use too much gas.
⚠️ Before You Begin (Safety First)
Engine components can be hot. Disconnect the battery before working on electrical parts. Wear gloves and eye protection. Don't touch moving engine parts.
Common Symptoms
- Check Engine Light is on
- Engine runs rich, sometimes rough
- Bad fuel mileage
- Engine might idle poorly
- Hesitation on acceleration
Common Causes
- Defective Manifold Air Temperature sensor
- Damaged wiring in the MAT sensor circuit
- Poor electrical connection at the sensor
- Short to ground in the MAT sensor circuit
- Faulty Powertrain Control Module (PCM) (rare)
Frequently reported on: Ford F-150 (2004-2008), Ford Ranger (1998-2011), Ford Explorer (2002-2005), Ford Focus (2000-2004)
Diagnostic Steps
- Locate the Manifold Air Temperature (MAT) sensor.
- Inspect the MAT sensor's electrical connector for corrosion or damage.
- Check the wiring leading to the sensor for frayed insulation or breaks.
- Use a multimeter to test the sensor's resistance at various temperatures.
- Verify voltage at the sensor connector from the PCM.
- If the sensor tests bad or wiring is damaged, replace the faulty component.
- Clear the code and test drive the vehicle.
👨🔧 When to Call a Professional
If you've checked the sensor and wiring and still have the code, you might have a PCM issue or a more complex wiring problem. That's when you bring it to a shop.
Commonly Asked Questions
Can I drive with a P1118 code?
Yeah, you can, but it's gonna run like crap and waste gas. Get it fixed. Don't wait too long.
Where is the MAT sensor located on a Ford?
Depends on the engine. It's usually in the intake manifold itself, or sometimes integrated into the air intake tube near the throttle body.
What's the difference between a MAT and an IAT sensor?
MAT measures air temp in the manifold, after the throttle. IAT usually measures air temp before it enters the engine, like in the airbox. P1118 is for the manifold temp.
Will replacing the MAT sensor always fix P1118?
Not always. Most times, yeah, it's the sensor. But sometimes it's the wiring. You gotta check both.
How do I test the MAT sensor with a multimeter?
You'll check resistance across its terminals. Resistance should drop as the sensor gets warmer. If it's way off, it's probably bad.