P0AAA: Hybrid/EV Battery Voltage Isolation Sensor Circuit High

What does P0AAA mean?

P0AAA is the high-side counterpart of P0AA9: the isolation sensor reports a rail-to-ground voltage above anything the pack can produce. GM's tables tie the limit to the pack: over 333 V in the 2016 table and over 416 V in the 2019 table, each in 320 of 400 samples with the bias switch open, Type B, two trips. The 2013 GM table instead flags a mid-pack reading that differs from the motor controller's voltage by more than 15 V. Likely sources are an open reference or ground in the measuring circuit or a failed input stage in the battery controller. No public bulletin from another maker names this code. The car usually stays drivable with warnings, but isolation monitoring is lost, and P0AA6 cannot be trusted until it is fixed.

The code tells you which monitor failed, not which part is broken. Test before replacing parts.

Symptoms

• Check engine and hybrid or EV warning lights
• Isolation monitoring disabled while the code is active

Common causes

• High Open ground or reference in the isolation measuring circuit
• Medium Failed isolation input stage in the battery controller
• Low Sense lead shorted to another HV potential inside the pack

Likelihood is a general estimate across vehicles; your make and model may differ.