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Powertrain Source reviewed Lights the check engine lamp

P0BC8: Hybrid/EV Battery Pack Cooling Fan 1 Sense Range/Performance

Standardized SAE J2012 code · P0Bxx — Hybrid and electric propulsion

Safety-critical system. Faults in airbags, brakes, steering or high-voltage components can put people at risk. Follow the manufacturer's service information and safety procedures, or have the vehicle checked by a qualified workshop.

What does P0BC8 mean?

P0BC8 compares the speed fed back by battery cooling fan 1 with what the controller commanded. GM's 2016 and 2018 hybrid tables run two checks. With the fan enabled at 11 to 89 % duty for more than 11 s, the filtered difference between commanded and reported speed must stay inside calibrated limits; large errors fail within seconds, small ones after up to 43 s. With the fan off for more than 20 s, a reported speed above 120 rpm fails in 24 of 32 samples at 250 ms. It is Type B, two trips, and waits while drive or sense circuit codes are active. A dusty or worn fan that cannot reach its speed is the usual cause; a fan turning while commanded off points to a stuck drive. The circuit cases are P0BC7, P0BC9 and P0BCA.

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

Symptoms

  • MIL on after two trips
  • Weak airflow or unusual fan noise from the battery intake
  • Reduced electric assist when the pack warms up

Common causes

  • High Dust-clogged impeller, blocked intake or worn fan bearing
  • Medium Fan keeps running while commanded off (stuck drive or relay)
  • Medium Fan electronics reporting a wrong speed

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

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