P1115
FordEngine Coolant Temperature (ECT) Sensor Circuit Intermittent High Voltage/Intake Air Temperature (IAT) Sensor - B Circuit High Input
Medium SeverityThis code indicates an intermittent high voltage condition in the circuit for either the Engine Coolant Temperature (ECT) sensor or the Intake Air Temperature (IAT) sensor. This can lead to incorrect fuel mixture calculations by the engine's computer, potentially affecting fuel economy and engine performance.
⚠️ Before You Begin (Safety First)
Always ensure the engine is cool before working on coolant systems to avoid burns. Disconnect the battery before performing any electrical work to prevent short circuits. Wear appropriate eye protection and gloves.
Common Symptoms
- Check Engine Light illumination
- Poor fuel economy
- Rough idle or stalling
- Difficulty starting, especially when cold
- Engine running rich (black smoke from exhaust)
- Engine running lean
- No significant driveability issues (intermittent nature)
Common Causes
- Faulty Engine Coolant Temperature (ECT) sensor
- Faulty Intake Air Temperature (IAT) sensor
- Corroded or loose electrical connectors at the sensor or PCM
- Wiring harness shorted to voltage or ground intermittently
- Open circuit in the sensor wiring
- Damaged PCM (Powertrain Control Module) - rare
Frequently reported on: Ford F-150 2000-2008, Ford Explorer 1999-2005, Ford Ranger 1998-2011, Ford Focus 2000-2007
Diagnostic Steps
- Visually inspect the Engine Coolant Temperature (ECT) sensor and Intake Air Temperature (IAT) sensor and their electrical connectors for signs of damage, corrosion, or loose connections.
- Carefully inspect the wiring leading to both sensors for any chafing, cuts, or areas where it might be shorting to other components or ground.
- With the engine cold, use a multimeter to test the resistance of the ECT sensor. Compare readings to factory specifications. Repeat for the IAT sensor.
- If either sensor tests out of specification, replace the faulty sensor. Ensure the new sensor is appropriate for your vehicle's make and model.
- After replacing any parts, clear the P1115 code using an OBD-II scanner and test drive the vehicle to see if the code returns.
👨🔧 When to Call a Professional
If you have replaced the sensor and checked wiring connections, but the intermittent P1115 code persists, it's time to consult a professional technician. Intermittent electrical issues can be challenging to diagnose without specialized diagnostic tools and expertise to trace wiring harnesses for breaks or shorts.
Commonly Asked Questions
Can I drive with a P1115 code?
While you might be able to drive with this code, it's not recommended for long periods. Incorrect temperature readings can cause the engine to run rich or lean, potentially damaging the catalytic converter or reducing fuel economy.
Is the ECT or IAT sensor more likely to be the cause?
Both sensors are equally possible culprits for P1115. A thorough diagnosis involves testing both sensors' circuits and resistances to pinpoint the exact failing component or wiring issue.
How difficult is it to replace an ECT or IAT sensor?
Replacing either sensor is generally an easy DIY task, often requiring only basic hand tools. The main difficulty lies in diagnosing which sensor or wiring is at fault, especially with intermittent issues.
What is 'intermittent high voltage' referring to?
Intermittent high voltage means that the electrical signal from the sensor to the engine's computer sporadically goes above its normal operating range, or briefly experiences a spike, indicating a temporary fault in the sensor or its wiring circuit.
Do I need to drain coolant to replace the ECT sensor?
Often, you only need to drain a small amount of coolant, or none at all if you work quickly to swap the sensor. Some coolant might spill, so have a drain pan ready. It's also a good time to check your coolant level and condition.