P0B4C: Hybrid/EV Battery Voltage Sense D Circuit Low

From the driver's seat P0B4C looks like a battery problem: the hybrid warning comes on and electric power is cut back. Technically it is a measuring fault on cell channel D, whose reading has fallen below what even a deeply discharged cell would show. GM's battery energy control module uses 0.2 V or less, held for 1.4 s within 2 s, Type A, and skips the test while open sense line or communication faults are active. On the 2012 two-mode full-size hybrids, channel D is block 4, and the code needs blocks 4 and 5 both below 2 V in 15 of 20 samples, Type B. A genuinely weak cell produces separate cell voltage codes, so P0B4C points to wiring or the monitoring module.

Symptoms

• Hybrid warning message and MIL
• Electric power and regeneration cut back
• Engine runs more often than usual

Most likely causes

• Short between channel D sense line and a neighbouring line
• Defective input on the cell monitoring module
• Corroded tap shared by blocks 4 and 5 (GM two-mode)

What to check, in order

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

1. Read the codes with a hybrid-compatible scanner and write down the freeze frame data
2. With the connector unplugged, check whether the signal wire is making contact with ground.
3. Make sure the battery cooling air intake is clean
4. Check the 12 V auxiliary battery, which can also trigger warnings
5. 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 P0B4C means

• P: Powertrain: engine and transmission
• 0: Generic code: same on every make
• B: Subsystem depends on the code range
• 4C: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0B4C?

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 P0B4C?

The most common causes are: short between channel D sense line and a neighbouring line; defective input on the cell monitoring module; corroded tap shared by blocks 4 and 5 (GM two-mode).

Related codes

• P0B4AHybrid/EV Battery Voltage Sense D Circuit
• P0B4BHybrid/EV Battery Voltage Sense D Circuit Range/Performance
• P0B4DHybrid/EV Battery Voltage Sense D Circuit High
• P0B4EHybrid/EV Battery Voltage Sense D Circuit Intermittent/Erratic
• P0B47Hybrid/EV Battery Voltage Sense C Circuit Low
• P0B51Hybrid/EV Battery Voltage Sense E Circuit Low

Sources

• gsi.ext.gm.com: 19OBDG01 Hybrid Diagnostics
• gsi.ext.gm.com: 12OBDG06 Hybrid Diagnostics
• law.cornell.edu: 13 CCR 1968.2

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.