P0BC1: Hybrid/EV Battery Pack Cooling Fan Supply Voltage Circuit High

P0BC1 flags voltage on the battery fan feed when there should be none, or more than expected. GM documents it for the battery pack control module of its Two-Mode hybrid SUVs and pickups (Tahoe, Yukon, Escalade, Silverado, Sierra; 2012 and 2013 tables) as a welded fan relay: with the fan commanded off, a fan monitor voltage of at least 0.9 V in 10 of 20 samples at 100 ms sets it, provided the 12 V system is between 9 and 18 V and no fan circuit code (P0A81) is active. It is Type B, MIL after two trips. A stuck relay keeps the fan running with the vehicle off and drains the 12 V battery. The open and low cases are P0BBF and P0BC0; a fan that keeps turning without this fault is P0A83.

High severity. Can I keep driving?If the car still runs, drive as little as possible and go to a specialized repair shop. Do not touch the orange cables: they carry high voltage.

Symptoms

MIL on after two trips
Battery fan keeps running after the vehicle is switched off
Discharged 12 V battery after standing

Most likely causes

Fan relay contacts welded closed
Fan feed shorted to a constant battery voltage wire
Relay control output in the module stuck on

What to check, in order

Start with the simplest. You can tick off each step.

Read the codes with a hybrid-compatible scanner and write down the freeze frame data
Check the sensor's ground and make sure the signal wire is not receiving voltage from another circuit.
Make sure the battery cooling air intake is clean
Check the 12 V auxiliary battery, which can also trigger warnings
Leave any high-voltage measurements to a specialized repair shop

Good to know

Repair difficulty: easy
It affects emissions.

What each character of P0BC1 means

P: Powertrain: engine and transmission
0: Generic code: same on every make
B: Subsystem depends on the code range
C1: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0BC1?

If the car still runs, drive as little as possible and go to a specialized repair shop. Do not touch the orange cables: they carry high voltage.

What causes code P0BC1?

The most common causes are: fan relay contacts welded closed; fan feed shorted to a constant battery voltage wire; relay control output in the module stuck on.

Related codes

Sources

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.