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Powertrain Source reviewed Lights the check engine lamp

P0BB4: Hybrid/EV Battery Voltage Sense Y Circuit Range/Performance

Standardized SAE J2012 code · P0Bxx — Hybrid and electric propulsion

Safety-critical system. Faults in airbags, brakes, steering or high-voltage components can put people at risk. Follow the manufacturer's service information and safety procedures, or have the vehicle checked by a qualified workshop.

What does P0BB4 mean?

P0BB4 is a plausibility code: the controller compares how the Y reading changes over time with the behaviour of all other cells. In the 16OBDG02 programme a sample counts as failed when the pack average moves by more than 0.022 V but Y has not trended at least 0.002 V the same way; 35 such results in 40 evaluations set a one-trip Type A fault. The 2019 hybrid powertrain control processor 2 uses the same frame with a 0.005 V trend. For the 2016 Volt the window is 7 s in 8 s. A frozen analogue input or a software problem in the battery controller are the typical findings, while a real cell defect is rarer. Unlike P0BB3, the signal is present, so the car usually keeps driving.

The code tells you which monitor failed, not which part is broken. Test before replacing parts.

Symptoms

  • MIL, vehicle still drivable
  • Battery power occasionally limited

Common causes

  • High Analogue input Y frozen at one value
  • Medium Battery controller software fault
  • Low Weak cell Y with sluggish voltage response

Likelihood is a general estimate across vehicles; your make and model may differ.

Add your car to see reports of P0BB4 on the same make and model first.

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