P0BCBHybrid/EV Battery Pack Cooling Fan 1 Sense Circuit Intermittent/Erratic
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P0BCB flags a speed feedback from battery cooling fan 1 that drops out or jumps in a way no rotating fan can, typically a loose contact in the feedback line. No manufacturer documents this exact code publicly; GM's 2016 and 2018 hybrid tables, which watch the same pulse feedback, list only performance, low and high (P0BC8, P0BC9, P0BCA). Toyota's battery cooling patents show the principle: the speed measured by a rotation sensor on the fan motor is compared with the target under steady command, so a jumping signal makes that comparison worthless. CARB requires the inputs of battery thermal management to be monitored. Wiggle-test the fan connector and harness. An open line is P0BC7; fan 2 has P0D63.
- What you may notice
- Hybrid system warning or MIL, sometimes coming and going
- Fan speed reading jumping on the scan tool
- Occasional power reduction
- Likely causes
- LikelyLoose or corroded terminal in the feedback circuit
- PossibleChafed harness near the fan or battery case
- RareIntermittent fault in the fan's speed sensor
- 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: €20 – €450
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.