P2186
Engine Coolant Temperature Sensor 2 Circuit Intermittent/Erratic
Engine coolant temperature sensor
Generic OBD-II
Medium
What it means
P2186 means the signal from engine coolant temperature sensor 2 is intermittent or erratic — jumping around rather than reading a steady value. It is a sensor/wiring fault, not proof the engine is overheating, and it most often traces to a loose or corroded connector or a failing sensor. It can affect cold-start fueling and temperature-gauge accuracy until fixed.
Medium
Can I keep driving? Usually drivable — this is a sensor-signal fault, not real overheating; you may see poor cold-start behavior or an erratic temperature reading.
Common symptoms
What you'll notice
- Check-engine light on
- Erratic or jumpy coolant temperature reading
- Harder cold starts or slightly rough cold running
- Cooling fans cycling at the wrong times
- Minor drop in fuel economy
Common causes
Most likely first
- Intermittent open or short in the ECT sensor 2 wiringLikely
- Poor or corroded connector at the sensorCommon
- Faulty engine coolant temperature sensor 2Common
- Faulty or corroded wiring/connections in the circuitLess often
How to diagnose & fix
Work through it in order
- Read freeze-frame and look for the temperature glitches captured when the code set.
- Wiggle-test the sensor connector and harness with the engine running while watching the live data for dropouts.
- Inspect the connector for corrosion, spread terminals, or a loose fit.
- Compare ECT sensor 2 against sensor 1 on a scan tool; they should read close when the engine is cold.
- If the wiring and connection are good, replace the coolant temperature sensor 2 and retest.
FAQ
Quick answers
Is it safe to drive with P2186?+
Usually yes. It reflects an unstable sensor signal rather than an actual overheating condition, though it can affect cold-start fueling, so repair it before it becomes a steady fault.
Can I just clear P2186?+
Because the fault is intermittent it may stay away briefly, but it returns once the loose connection or failing sensor acts up again.
Related codes
Often seen with P2186
Read & clear P2186 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX