Powertrain
Manufacturer-specific
OBD-II Fault Code
P1115: Engine Coolant Temperature (ECT) Sensor Circuit Intermittent High Voltage/IAT - B Circuit High Input
Meaning, symptoms, likely causes, diagnostic checks and repair guidance for P1115.
Cooling system
Use this category to narrow your checks before replacing parts.
High
Severity is a general guide. Confirm with scan-tool data and vehicle symptoms.
What P1115 usually means
Engine Coolant Temperature (ECT) Sensor Circuit Intermittent High Voltage/IAT - B Circuit High Input.
Common symptoms
Check Engine light; Poor drivability or reduced fuel economy depending on fault; Temperature gauge abnormal; Overheating or slow warm-up possible
Likely causes
Low coolant; Faulty thermostat; Coolant temperature sensor/wiring fault; Cooling fan issue; High signal voltage; Open ground; Short to voltage; Failed sensor; Loose connector; Moisture/corrosion; Harness vibration fault
Diagnostic checks
Scan all modules and record freeze-frame data before clearing codes; Check battery voltage and related fuses; Check coolant level only when engine is cool; Compare scan-tool temperature to actual temperature; Check sensor ground and signal circuit for short to voltage; Wiggle-test harness while watching live data; Inspect for water intrusion/corrosion
Repair guidance
Repair leaks, replace thermostat/sensor/fan component after confirming fault; Repair ground/signal circuit or replace confirmed faulty sensor; Clean/secure connector and repair damaged harness
Verification after repair
Clear code, road-test through the same drive condition, then rescan