What does it mean?
P1115 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: ECT Sensor Circuit High Input (Intermittent) .
Symptoms
- Check engine light that comes and goes across several drive cycles
- Coolant temperature in live data dropping to an extremely cold value for a moment
- Temperature gauge dipping suddenly and then recovering
- Rich running with black smoke and a fuel smell during the fault
- Cooling fans running when they should be off, as the module falls back to a default
- Higher fuel consumption and a rough idle when the glitch occurs
Likely causes
- Loose or spread terminal in the coolant temperature sensor connector
- Broken strands in the signal or ground wire that separate as the engine moves on its mounts
- Sensor element that opens internally once it is hot
- Corrosion raising the contact resistance for short moments
- Connector latch broken so the plug backs off slightly with vibration
- Poor engine ground for the sensor return circuit
- Damaged harness at a clip or where it passes a heat source
How to fix it
- Graph the coolant temperature during a road test and mark the moments the value drops out
- Wiggle the connector and the harness with the engine idling while watching the value to reproduce the fault
- Bridge the two connector pins briefly with the ignition on — the reading should go to maximum, confirming the wiring and module are good
- Inspect the connector for spread terminals, a broken lock and corrosion; restore terminal tension
- Measure the sensor resistance cold and at operating temperature against the specification
- Voltage-drop test the ground path while the fault is present
- Repair the wiring or replace the sensor, then confirm the warm-up curve is smooth with no dropouts