P0BAB: Hybrid/EV Battery Voltage Sense W Circuit Low

A W channel reading at or near zero sets P0BAB. How low is too low depends on the battery: GM's lithium-ion modules of 2016 and 2019 react to 0.2 V or less held for 1.4 s within a 2 s window, Type A, and the 16OBDG02 programme to under 0.20 V in 14 of 18 samples at 100 ms. The eAssist mild hybrid already fails below 1.4 V, seven of ten samples, as long as the 12 V supply exceeds 8.8 V and P1B38 is not active; that fault is Type B. All of these tests stand down while an open sense line fault is present, so a simply broken lead shows up as P0BA9. P0BAB on its own suggests a short towards a lower potential, a dead measuring input or a deeply discharged cell. Power and charging are usually restricted.

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

Hybrid or EV warning and MIL
Reduced power output
Charging limited or blocked

Most likely causes

Sense lead W shorted to a lower cell potential
Measuring input for W on the monitoring board failed
Cell W deeply discharged or internally shorted

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
With the connector unplugged, check whether the signal wire is making contact with ground.
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 P0BAB means

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

Frequently asked questions

Can I keep driving with code P0BAB?

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 P0BAB?

The most common causes are: sense lead W shorted to a lower cell potential; measuring input for W on the monitoring board failed; cell W deeply discharged or internally shorted.

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.