P0BB3: Hybrid/EV Battery Voltage Sense Y Circuit

P0BB3 reports that the sense lead of channel Y, the twenty-fifth cell group, is no longer properly connected. GM's 16OBDG02 programme does not wait for odd voltages but calculates the resistance of the sense line and fails it above 30.00 in seven of nine samples, which is a one-trip Type A fault; the unit is missing in the table. The 2019 battery energy control module instead looks at the cell voltages themselves, for example 1.3 V between neighbours or a reading below 36 mV while that cell is being balanced, with 0.8 s of failure in 1.6 s. The eAssist mild hybrid sets it as a Type B fault when lines N and N-1 both read under 1.4 V and jump by more than 0.5 V. Low and high monitors for Y are blocked while P0BB3 is active.

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 and high-voltage system warning
Vehicle may not start in electric mode
Charging aborted

Most likely causes

Open circuit in sense lead Y
Corroded or loose terminal raising line resistance at Y
Cell monitoring slave board fault on input Y

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
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

It can trigger limp mode.
It affects emissions.

What each character of P0BB3 means

P: Powertrain: engine and transmission
0: Generic code: same on every make
B: Subsystem depends on the code range
B3: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0BB3?

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 P0BB3?

The most common causes are: open circuit in sense lead Y; corroded or loose terminal raising line resistance at Y; cell monitoring slave board fault on input Y.

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.