Fault Family System: Powertrain (P-Codes) 12 SAE Codes

HV Battery Isolation Fault

Diagnostic & Technical Explanation

Code P0AA6 sets when the HV battery isolation monitoring circuit detects a resistance path between the high-voltage bus and chassis ground that is lower than the safe threshold, or the isolation-monitoring circuit itself fails its self-test. The same monitor can report this fault specifically while an external EVSE is connected and charging, if the leakage path traced back is on the charger side of the bus rather than the pack or drive side. The most common physical causes are moisture intrusion into a HV connector or the battery pack seal, a damaged HV cable jacket rubbing against a chassis ground point, and a failed isolation-monitor module.

These 12 diagnostic trouble codes share one detection mechanism and one repair path, which is why MechanicDB groups them into a single authored fault family rather than repeating the same explanation 12 times.

Codes in this family (12)

Code	Definition	Repair coverage
P0AA6	Hybrid/EV Battery Voltage System Isolation Fault	3 ranked fixes
P0AA7	Hybrid/EV Battery Voltage Isolation Sensor Circuit	3 ranked fixes
P0AA8	Hybrid/EV Battery Voltage Isolation Sensor Circuit Range/Performance	3 ranked fixes
P0AA9	Hybrid/EV Battery Voltage Isolation Sensor Circuit Low	3 ranked fixes
P0AAA	Hybrid/EV Battery Voltage Isolation Sensor Circuit High	3 ranked fixes
P0AAB	Hybrid/EV Battery Voltage Isolation Sensor Circuit Intermittent/Erratic	3 ranked fixes
P0DAA	Battery Charging System Isolation Fault	3 ranked fixes
P0E74	Hybrid/EV Battery Voltage Internal Isolation Fault	3 ranked fixes
P2C85	Hybrid/EV Battery Voltage External Isolation Fault	3 ranked fixes
P2C86	Hybrid/EV Battery Voltage Internal Isolation Warning	3 ranked fixes
P2C87	Hybrid/EV Battery Voltage External Isolation Warning	3 ranked fixes
P2C88	Hybrid/EV Battery Voltage System Isolation Warning	3 ranked fixes

What this page does not show

This page publishes the fault mechanism and the code index. The licensed dataset adds, for every one of the 15,886 codes, the full authored repair set (56,729 procedures in total) with the fields deliberately withheld here:

Procedures 2..n after the first-listed procedure
Aftermarket parts cost ranges in USD (est_parts_cost_min/max_usd)
Professional labor-hour estimates (est_labor_hours)
Step-by-step diagnostic and repair instructions
Replacement-part mappings and catalog lookups
6,637 manufacturer-specific OEM codes across 32 makes ($149 tier)

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