P2186: Engine Coolant Temperature Sensor 2 Circuit Intermittent/Erratic

What does P2186 mean?

P2186 covers a sensor 2 signal that jumps instead of changing smoothly. Coolant temperature moves slowly because of the mass of the liquid, so a step faster than physics allows points to a loose contact rather than a real change. GM's 2019 tables (19OBDG03D) work out an upper and lower limit for each new reading from the previous value and the sensor's time constant, about 7.4 s for sensor 2 within a -60 to 150 °C window; a reading outside this corridor for 5 s within 6 s sets the code as Type B, MIL after two trips. GM also lists P2186 among the effects of the chafed engine harness in bulletin 21-NA-149. Typical causes are worn connector pins, a wire broken inside the insulation or a sensor with an intermittent element. Steady low or high signals are P2184 and P2185.

The code tells you which monitor failed, not which part is broken. Test before replacing parts.

Symptoms

• Check engine light after two drives
• Fans switching on and off irregularly
• Temperature-related messages that appear and vanish

Common causes

• High Worn or loose pins in the sensor 2 connector
• Medium Wire broken inside its insulation or chafed harness making intermittent contact
• Low Sensor 2 with an intermittent internal fault

Likelihood is a general estimate across vehicles; your make and model may differ.