P0B8D: Hybrid/EV Battery Voltage Sense Q Circuit Low

P0B8D reports a voltage on sense Q below the lowest credible cell value. GM's lithium-ion battery controllers in the 2016 and 2019 tables use 0.2 V or less for 1.4 s within 2 s, Type A, and the 2016 program with a separate sense module 0.20 V with 14 of 18 samples. GM's BAS Plus mild hybrid applies 1.4 V, 7 of 10 samples, Type B. In the 2012 two-mode NiMH pack Q is block 17 and the battery pack control module requires blocks 17 and 18 both under 2 V for 15 of 20 samples. The low test is suppressed while an open-line fault is active, so P0B8B takes precedence for a broken lead. Shorts in the sense path are the leading cause; a real deep discharge of the cell would normally trigger further battery codes too.

Symptoms

• MIL and reduced power mode
• Engine runs more often on hybrids

Most likely causes

• Short in the Q sense path to a lower potential
• Sense module input reading low
• Cell or block 17 deeply discharged

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 P0B8D means

• P: Powertrain: engine and transmission
• 0: Generic code: same on every make
• B: Subsystem depends on the code range
• 8D: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0B8D?

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 P0B8D?

The most common causes are: short in the Q sense path to a lower potential; sense module input reading low; cell or block 17 deeply discharged.

Related codes

• P0B8BHybrid/EV Battery Voltage Sense Q Circuit
• P0B8CHybrid/EV Battery Voltage Sense Q Circuit Range/Performance
• P0B8EHybrid/EV Battery Voltage Sense Q Circuit High
• P0B8FHybrid/EV Battery Voltage Sense Q Circuit Intermittent/Erratic
• P0B88Hybrid/EV Battery Voltage Sense P Circuit Low
• P0B92Hybrid/EV Battery Voltage Sense R Circuit Low

Sources

• gsi.ext.gm.com: 16OBDG01 Hybrid Diagnostics
• gsi.ext.gm.com: 19OBDG01 Hybrid Diagnostics
• gsi.ext.gm.com: 16OBDG02 Hybrid Diagnostics
• gsi.ext.gm.com: 13OBDG05C Hybrid Diagnostics

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.