P0116
Engine Coolant Temperature Sensor Circuit 1 Range/Performance Problem
The engine computer does not trust the coolant temperature sensor reading. The signal may be slow, erratic, or unrealistic compared with actual engine warm-up. Common causes are a bad ECT sensor, low coolant, thermostat problems, or wiring faults.
- SEV
- 3/5
- DRIVE
- CAUTION
- DIY
- $15-$120
- SHOP
- $120-$400
Quick answer
AI-CITATION READYWhat it means
Can you drive with it?
Most common causes
- Faulty engine coolant temperature sensor
- Low coolant level or air pocket around the sensor
- Thermostat stuck open or stuck closed
Typical repair cost
DIY usually runs $15-$120. Typical shop repair lands around $120-$400, depending on the root cause.
01 / Definition
P0116 means the PCM has detected that the engine coolant temperature sensor circuit 1 signal is outside the expected operating range or is not performing correctly. The PCM expects coolant temperature to rise and respond in a predictable way after startup. If the reading changes too slowly, too quickly, or does not match other engine conditions, it sets P0116.
02 / Drive status
With caution. Short trips are usually possible, but the engine may run rich, start poorly, or control the cooling fans incorrectly. Do not ignore it because bad temperature data can hide a real overheating problem.
03 / Symptoms
- Check engine light
- Hard starting
- Poor fuel economy
- Rough idle
- Cooling fan running too often or not enough
- Temperature gauge acting wrong
- Heater performance may be poor
- Possible overheating or cold-running symptoms
04 / Causes
| 1 | Faulty engine coolant temperature sensor | high |
|---|---|---|
| 2 | Low coolant level or air pocket around the sensor | high |
| 3 | Thermostat stuck open or stuck closed | medium |
| 4 | Damaged, loose, or corroded ECT sensor connector or wiring | medium |
| 5 | Cooling fan running at the wrong time or cooling system problem | low |
| 6 | PCM fault or reference voltage issue | low |
05 / Diagnostic sequence
- 01Check coolant level and inspect for leaks before testing the sensor.
- 02Compare ECT reading to ambient temperature on a cold engine using scan data.
- 03Watch coolant temperature rise during warm-up and compare it with gauge behavior and engine conditions.
- 04Inspect the ECT connector and wiring for corrosion, coolant intrusion, damaged insulation, or loose terminals.
- 05Test sensor resistance and compare it to the manufacturer temperature chart.
- 06Check thermostat operation if the engine warms too slowly or overheats.
- 07Verify cooling fan operation and confirm the fan is not running constantly because of another fault.
- 08Repair the confirmed fault, clear the code, and recheck during a full warm-up cycle.
06 / Repairs
| 1 | Top off coolant, repair leaks, and bleed air from the cooling system | $10-$150 |
|---|---|---|
| 2 | Repair or replace damaged ECT sensor wiring or connector terminals | $20-$150 |
| 3 | Replace the engine coolant temperature sensor if it fails testing | $20-$120 |
| 4 | Replace a stuck thermostat or repair cooling system faults affecting temperature control | $80-$350 |
| 5 | Diagnose PCM or reference voltage faults only after sensor and cooling system checks pass | $100-$400 |
07 / Related codes
08 / FAQ
What does P0116 mean?
It means the coolant temperature sensor signal is not behaving the way the PCM expects.
Can low coolant cause P0116?
Yes. Low coolant or air around the sensor can make the reading unstable or inaccurate.
Can a thermostat cause P0116?
Yes. A thermostat stuck open or closed can make coolant temperature change incorrectly.
Will P0116 cause overheating?
The code itself does not overheat the engine, but it can hide a real cooling system problem or affect fan control.
09 / Source and method
- DATA BASIS
- OBD-II REFERENCE + OBD2.HELP
- METHOD
- STATIC VALIDATION
- SAFETY
- INFORMATIONAL
This page combines OBD-II diagnostic reference data with OBD2.help generated diagnostic guidance for code meaning, likely causes, and repair direction.
Publishing uses deterministic schema and build validation, plus manual spot checks on representative pages before release.
Safety-critical diagnosis and repairs should be confirmed with a qualified mechanic, especially when the vehicle is misfiring, overheating, or losing power.