Powertrain, generic · Hybrid propulsion

P0BAB Hybrid/EV Battery Voltage Sense W Circuit Low

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

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.

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

Symptoms

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

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€100–6,000
Time1–8 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

hv battery voltage sense wwiring harnessbms

Related codes

P0BA9P0BAAP0BACP0BADP0BA6P0BB0

References: gsi.ext.gm.com, gsi.ext.gm.com, gsi.ext.gm.com.