Powertrain, generic · Hybrid propulsion

P0AA6 Hybrid/EV Battery Voltage System Isolation Fault

Check engine lightOn
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

The high-voltage system floats free of the chassis, and an isolation monitor measures the resistance from each HV rail to body ground. P0AA6 sets when that resistance falls below a calibrated limit. GM tables measure with the contactors open and fail below 75,000 ohms (2016) or 213,000 ohms (2019), Type A, one trip; Volt bulletins expect over 275 kOhm after repair, while FMVSS 305 sets 100 ohms per volt DC as the post-crash floor. Documented causes: Volt battery coolant leaks, a chafed HV harness on Ford Aviator/Explorer hybrids, a traction motor coolant leak on the 2017 Ioniq Hybrid; Toyota adds INF codes naming the area. P0AA7 to P0AAB flag the measuring circuit itself. Expect warnings, no charging or a stop-safely message.

Likely causes

Coolant or moisture inside the battery pack, inverter or drive motor
Chafed or crushed orange HV cable shorting to the body
Insulation breakdown in the electric A/C compressor or a motor winding
Electrolyte leakage or contamination inside the battery sections

Symptoms

  • Check engine and hybrid or EV system warning lights
  • Vehicle will not charge or will not enter ready mode after restart
  • Stop safely now message or reduced power

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€200–8,000
Time2–14 h

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

Parts involved

hv batteryhv cablinginvertercharger

Related codes

P0AA7P0AA8P0DAAP0A5FP0A62P0A65

References: gsi.ext.gm.com, gsi.ext.gm.com, static.nhtsa.gov, static.nhtsa.gov.