Powertrain
Generic/SAE
OBD-II Fault Code
P0117: Engine Coolant Temperature Circuit Low Input
Meaning, symptoms, likely causes, diagnostic checks and repair guidance for P0117.
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 P0117 usually means
Engine Coolant Temperature Circuit Low 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; Low signal voltage; Weak power supply; High resistance/poor ground; Failed sensor
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 reference voltage, ground and signal voltage
Repair guidance
Repair leaks, replace thermostat/sensor/fan component after confirming fault; Repair poor ground/power feed or replace confirmed faulty sensor
Verification after repair
Clear code, road-test through the same drive condition, then rescan