P0B9C: Hybrid/EV Battery Voltage Sense T Circuit Low

P0B9C signals that sense T reads too low. On the 2012 two-mode trucks this is block 20, and because no block 21 exists the low test there looks at block 20 alone: below 2 V in 15 of 20 samples, Type B, while channels R and S each need their upper neighbour to read low as well. GM's lithium-ion controllers from the 2016 Volt to 2019 work with 0.2 V or less for 1.4 s within 2 s, Type A, the 16OBDG02 programme with under 0.20 V in 14 of 18 samples, and the eAssist mild hybrid with 1.4 V in 7 of 10 samples, Type B. Open sense line faults are evaluated first. For the driver the result is a warning and reduced power until the cause is repaired.

Symptoms

• MIL and hybrid warning
• Reduced power, engine may not shut off on hybrids

Most likely causes

• Sense lead T shorted to ground or a lower potential
• Weak or discharged NiMH block 20 on two-mode packs
• Failed measuring input for channel T

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 P0B9C means

• P: Powertrain: engine and transmission
• 0: Generic code: same on every make
• B: Subsystem depends on the code range
• 9C: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0B9C?

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 P0B9C?

The most common causes are: sense lead T shorted to ground or a lower potential; weak or discharged NiMH block 20 on two-mode packs; failed measuring input for channel T.

Related codes

• P0B9AHybrid/EV Battery Voltage Sense T Circuit
• P0B9BHybrid/EV Battery Voltage Sense T Circuit Range/Performance
• P0B9DHybrid/EV Battery Voltage Sense T Circuit High
• P0B9EHybrid/EV Battery Voltage Sense T Circuit Intermittent/Erratic
• P0B97Hybrid/EV Battery Voltage Sense S Circuit Low
• P0BA1Hybrid/EV Battery Voltage Sense U Circuit Low

Sources

• gsi.ext.gm.com: 12OBDG06 Hybrid Diagnostics
• gsi.ext.gm.com: 16OBDG01 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.