P0BC9Hybrid/EV Battery Pack Cooling Fan 1 Sense Circuit Low
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- Needs a drive cycle to confirm a fix
- How the car detects it
- P0BC9 means the speed feedback of battery cooling fan 1 is implausibly low while the fan is running. GM evaluates the feedback as a frequency: in its 2016 and 2018 hybrid tables the code counts a failure when the frequency stays below 8 Hz with the fan enabled at 11 to 89 % duty for more than 8 s and system voltage above 10.2 V; 16 failures in 20 samples at 250 ms set it as Type B, two trips. A frequency near zero comes either from a fan that is not turning or from a feedback line shorted to ground or interrupted. The high case is P0BCA, a speed that is merely too far from the target is P0BC8, and drive circuit faults are P0A81 to P0A85. Expect power limits when the pack warms up.
- What you may notice
- MIL on after two trips
- No airflow from the battery cooling fan
- Reduced power when the battery gets warm
- Likely causes
- LikelyFan seized, blocked or without power
- PossibleFeedback wire shorted to ground or interrupted
- PossibleFailed speed sensor inside the fan unit
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Often possible to do yourself.Typical cost: €40 – €500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.