Corroded, loose or damaged connector or terminals in the fan supply circuit; Open circuit, high resistance or chafed wiring in the fan power or ground feed; Blown fuse or failed relay supplying the battery cooling fan; Failing fan motor drawing excessive current and pulling the supply voltage down; Low 12 V auxiliary battery voltage or weak DC-DC converter output; Faulty fan control module or battery control unit output stage; Outdated control unit software where the manufacturer has issued a correction for this fault.

P0BC0

Hybrid/EV Battery Pack Cooling Fan Supply Voltage Circuit Low.

Generic
Powertrain
Generic code
Medium severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
B: AreaHybrid propulsion
C0: FaultThe specific fault in that area

What it means

P0BC0 is a generic powertrain code meaning the hybrid or EV control unit has detected the supply voltage to the traction battery pack cooling fan circuit is lower than expected. The control unit monitors the fan's supply voltage and sets the code when it falls below the calibrated threshold, usually with the fan commanded on. Exact fan layout, monitoring strategy and which module sets the code vary by model.

Symptoms

Hybrid or EV system warning light or malfunction indicator lamp on
Battery cooling fan not running or running weakly
Noticeably louder or quieter fan than normal
Reduced power or limited hybrid/EV assistance in hot conditions
Battery temperature warnings or reduced charging rate
Car may enter a limp or protective mode

Possible causes

Corroded, loose or damaged connector or terminals in the fan supply circuitlikely
Open circuit, high resistance or chafed wiring in the fan power or ground feedlikely
Blown fuse or failed relay supplying the battery cooling fanpossible
Failing fan motor drawing excessive current and pulling the supply voltage downpossible
Low 12 V auxiliary battery voltage or weak DC-DC converter outputpossible
Faulty fan control module or battery control unit output stagerare
Outdated control unit software where the manufacturer has issued a correction for this faultrare

How to diagnose

Read all stored and pending codes and note any related 12 V system, DC-DC converter or fan speed codes
Review freeze frame data for fan command, battery temperature and system voltage when the code set
Check the 12 V auxiliary battery condition and charging voltage, as low system voltage can trigger this code
Inspect the fan fuse and relay, and check the fan ducting and intake for blockage or debris
Inspect the fan wiring and connectors for corrosion, water ingress, heat damage and pushed-back pins
Using the scan tool's bidirectional controls, command the fan on and watch the fan speed and supply voltage
Measure supply voltage and ground voltage drop at the fan connector with the fan commanded on, following the manufacturer's wiring diagram
Check fan motor current draw against specification, and check for any applicable software updates for the model

How to fix

Clean, repair or replace corroded or damaged connectors and terminals
Repair or replace damaged wiring in the fan supply or ground circuit
Replace the blown fuse only after finding the cause, or replace a faulty relay
Replace the battery cooling fan if it is seized, noisy or drawing excessive current
Restore the 12 V supply by replacing a weak auxiliary battery or repairing the DC-DC converter
Replace or reprogram the controlling module only if testing confirms a fault or a manufacturer update applies

Can I keep driving?

Medium severity

The car can usually be driven for a short time, but without proper battery cooling the pack may overheat and the car may limit power. Have it checked soon and avoid hot weather, heavy loads or long journeys until repaired.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.