P0AABHybrid/EV Battery Voltage Isolation Sensor Circuit Intermittent/Erratic
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Can trigger limp mode
- Needs a drive cycle to confirm a fix
- How the car detects it
- 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.
- What you may notice
- Hybrid or EV warning lights that come and go
- Occasional power limitation that clears after restart
- Likely causes
- LikelyElectrical noise misinterpreted by controller software
- PossibleLoose or corroded sense connector at the battery controller
- RareFailing isolation measuring circuit inside the controller
- Repair
- Workshop only · Usually a job for a workshop.Typical cost: €100 – €2,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.