The Problem
2022 Polestar 2 Dual Motor (53,700 miles) brought in with 'High Voltage System Fault' and P0AA6. Coolant reservoir noticeably low. Vehicle would not enter Drive.
Diagnostic Procedure
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1. Confirm P0AA6. HV positive bus isolation: 16 kΩ. Negative bus: >1 MΩ.
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2. Positive bus fault. Segment: disconnect positive bus at battery junction. Isolation jumps to >1.2 MΩ after disconnecting the battery management system (BMS) harness connector at the rear underbody. Fault in BMS connector area.
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3. Inspect BMS connector (rear underfloor access). Coolant residue around connector housing and penetrating the connector seals. Coolant bridging HV positive sense wire to chassis ground inside the connector.
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4. Trace coolant source. Electric coolant pump (located 200mm forward of BMS connector) shows visible shaft seal weeping — coolant running along the pump body and dripping onto the BMS connector below.
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5. Replace coolant pump. Clean BMS connector with deionized water, dry thoroughly, apply dielectric grease.
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6. Refill and bleed coolant system.
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7. HV isolation: positive bus >1.8 MΩ. Clear P0AA6. Vehicle enters Drive.
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8. 25-mile test drive including highway. No fault return.
Resolution & Root Cause
Coolant pump replaced. BMS connector cleaned and protected. Isolation restored. P0AA6 resolved.
💡 Key Lesson
Polestar 2 P0AA6 with coolant loss — the battery coolant pump shaft seal is a known wear item from approximately 50,000 miles. The pump is positioned directly above the BMS harness connector, making coolant contamination of the connector the most common isolation fault path on this platform. Replace the pump, clean the connector, don't touch the battery pack.
About This Case
This case was solved remotely by an HVDesk specialist with 15+ years of hands-on experience across major EV platforms including Tesla, Hyundai/Kia, Volkswagen ID series, BMW i-series, and Ford EVs. The procedure was provided as structured remote support to an independent auto repair shop.
