Powertrain, generic · Hybrid propulsion

P0AAB Hybrid/EV Battery Voltage Isolation Sensor Circuit Intermittent/Erratic

Check engine lightOn
EmissionsNot relevant
Drive cycleRequired
Limp modePossible

P0AAB covers an isolation sensor signal that jumps or drops out briefly instead of staying wrong. No manufacturer documents this code publicly; GM's hybrid tables use only P0AA7 to P0AAA for the measuring circuit. CARB requires hybrid input components to be monitored for circuit and rationality faults, which is the basis for this code. The best public analogue is Mitsubishi's 2018 Outlander PHEV campaign, where noise from the shift selector, brakes or A/C made the sub-BMU misjudge its leak detection circuit, setting P0AA7 to P0AA9. Check for software updates, then for loose connectors at the battery controller. Erratic readings can mask a true insulation fault (P0AA6). Expect warnings that come and go.

Likely causes

Electrical noise misinterpreted by controller software
Loose or corroded sense connector at the battery controller
Failing isolation measuring circuit inside the controller

Symptoms

  • Hybrid or EV warning lights that come and go
  • Occasional power limitation that clears after restart

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€100–2,500
Time0.5–4 h

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

Parts involved

hv battery voltage isolation sensorwiring harnessbms

Related codes

P0AA7P0AA8P0AA9P0AAAP0AA6

References: law.cornell.edu, static.nhtsa.gov, gsi.ext.gm.com.