Coolant leak reaching high-voltage parts (RepairPal; Toyota's manual says a reading of several hundred kilohms strongly suggests fluid such as coolant). Failed high-voltage control module (RepairPal), such as the inverter with converter assembly (Toyota). Wiring problems (RepairPal), including damaged high-voltage motor, generator or frame cables, or a cable touching metal (Toyota). Insulation breakdown in the HV battery, battery ECU or battery smart unit, system main relays or junction block (Toyota INF 612). Insulation breakdown in the electric A/C compressor (Toyota INF 611). Insulation breakdown in the hybrid transaxle motor/generator (Toyota INF 613).

Find and repair the coolant leak and dry or replace any affected high-voltage part (RepairPal, Toyota). Repair or replace damaged high-voltage cables or harnesses (RepairPal, Toyota). Replace the part that fails the insulation test: inverter with converter assembly, electric A/C compressor, transaxle, battery ECU or junction block, or HV battery assembly (Toyota). Replace a failed high-voltage control module (RepairPal).

P0AA6🔧 Hybrid high-voltage (HV) system insulation monitoring: HV battery, inverter, motor/generator cables, transaxle and electric A/C compressorStop and fix promptly

P0AA6: Hybrid Battery Voltage System Isolation Fault (Meaning, Causes, Fixes)

Q: What does P0AA6 mean?

P0AA6 means the hybrid system has detected that the high-voltage circuit is no longer properly insulated from the rest of the car. Toyota's repair manual describes it as decreased insulation resistance between the high-voltage circuit and the body, and RepairPal lists coolant leaks, a failed high-voltage control module and wiring problems as common causes. In a hybrid, the high-voltage system is kept electrically isolated from the 12-volt system and the vehicle's frame. A monitor in the hybrid system keeps checking that isolation; Toyota's manual says the power management control ECU watches the battery smart unit for insulation faults. P0AA6 sets when that insulation drops. The sources word this differently: RepairPal says the code sets when excessive voltage is detected on the low-voltage side, while Toyota says it sets when insulation resistance between the high-voltage circuit and the body has decreased. On Toyota hybrids an information (INF) code narrows down where: INF 526 is the general code stored first, and on a following trip INF 611 points to the electric A/C compressor, 612 to the HV battery area, 613 to the transaxle, motor/generator cables and inverter, and 614 to the high-voltage DC area (2006 and 2010 Prius repair manuals). The sources also differ on severity: RepairPal says the high-voltage system may shut down, while Toyota's 2010 Prius manual says the vehicle cannot start once the code is stored.

Q: Can I keep driving with P0AA6?

Stop and fix promptly. Treat this as urgent. RepairPal rates P0AA6 Urgent and says the high-voltage system may shut down. Toyota's 2010 Prius repair manual goes further: if P0AA6 is stored, the vehicle cannot start. The code means high voltage may be leaking toward the car's body, so do not open the hybrid battery, inverter or orange cables yourself. This is a job for a hybrid-trained technician.

Reviewed 2026-10-22 · Based on 4 cited source(s)

What P0AA6 means

In a hybrid, the high-voltage system is kept electrically isolated from the 12-volt system and the vehicle's frame. A monitor in the hybrid system keeps checking that isolation; Toyota's manual says the power management control ECU watches the battery smart unit for insulation faults. P0AA6 sets when that insulation drops. The sources word this differently: RepairPal says the code sets when excessive voltage is detected on the low-voltage side, while Toyota says it sets when insulation resistance between the high-voltage circuit and the body has decreased. On Toyota hybrids an information (INF) code narrows down where: INF 526 is the general code stored first, and on a following trip INF 611 points to the electric A/C compressor, 612 to the HV battery area, 613 to the transaxle, motor/generator cables and inverter, and 614 to the high-voltage DC area (2006 and 2010 Prius repair manuals). The sources also differ on severity: RepairPal says the high-voltage system may shut down, while Toyota's 2010 Prius manual says the vehicle cannot start once the code is stored.

Severity: can I keep driving?

Stop and fix promptly

Treat this as urgent. RepairPal rates P0AA6 Urgent and says the high-voltage system may shut down. Toyota's 2010 Prius repair manual goes further: if P0AA6 is stored, the vehicle cannot start. The code means high voltage may be leaking toward the car's body, so do not open the hybrid battery, inverter or orange cables yourself. This is a job for a hybrid-trained technician.

Common symptoms

Check engine light (malfunction indicator lamp) on (Toyota bulletin 04506)
High-voltage (hybrid) system may not operate (RepairPal)
Hybrid battery will not charge (RepairPal)
Vehicle will not start once the code is stored, on the 2010 Prius (Toyota repair manual)

Likely causes

Roughly most to least common, based on the sources below. Your vehicle may differ.

Coolant leak reaching high-voltage parts (RepairPal; Toyota's manual says a reading of several hundred kilohms strongly suggests fluid such as coolant)
Failed high-voltage control module (RepairPal), such as the inverter with converter assembly (Toyota)
Wiring problems (RepairPal), including damaged high-voltage motor, generator or frame cables, or a cable touching metal (Toyota)
Insulation breakdown in the HV battery, battery ECU or battery smart unit, system main relays or junction block (Toyota INF 612)
Insulation breakdown in the electric A/C compressor (Toyota INF 611)
Insulation breakdown in the hybrid transaxle motor/generator (Toyota INF 613)

Diagnostic steps you can do

⚠ Before you start

Work on a cool engine, parked on level ground with the parking brake set. Never work under a car supported only by a jack.

Read all codes with a scanner that shows Toyota/Lexus INF (information) codes, and write them down. Don't clear P0AA6 INF 526 before a shop sees it: per the 2006 Prius repair manual, the more specific INF 611 to 614 code is stored on the next trip.
Check the engine and inverter coolant levels and look for coolant leaks from outside the components, without opening anything. RepairPal lists coolant leaks as a cause.
Check for technical service bulletins and hybrid component warranty coverage with the dealer. Toyota issued bulletin 04506 for 2004-2007 Prius with P0AA6 INF 526 and 613.
Do not open the HV battery, inverter or orange cables. Toyota's procedure requires insulated gloves, removing the service plug grip and waiting at least 10 minutes for the inverter capacitor to discharge, then testing with a 500 V megohmmeter.

Typical fixes

Find and repair the coolant leak and dry or replace any affected high-voltage part (RepairPal, Toyota)
Repair or replace damaged high-voltage cables or harnesses (RepairPal, Toyota)
Replace the part that fails the insulation test: inverter with converter assembly, electric A/C compressor, transaxle, battery ECU or junction block, or HV battery assembly (Toyota)
Replace a failed high-voltage control module (RepairPal)

Repair costs vary widely by vehicle, region, parts brand and shop, so we don't quote prices. Get a written estimate after diagnosis.

🛠 When to call a pro

Always: finding an isolation fault means testing live high-voltage parts with a 500 V megohmmeter
The car will not start or the hybrid system has shut down
You see coolant around the inverter, battery or high-voltage cables
You need a dealer-level scanner (Toyota Techstream or similar) to read INF codes and live insulation data

Where to buy

Plain search links. Always match parts to your exact year, make, model and engine.

OBD2 scanners on Amazon Parts at Advance Auto Parts catalog at RockAuto

FAQs

Is P0AA6 serious?

Yes. RepairPal rates it Urgent, and on the 2010 Prius Toyota says the vehicle cannot start once it is stored. It means the high-voltage system's insulation has weakened.

Can I drive with P0AA6?

Often you can't: the hybrid system may shut down (RepairPal) or the car may not start (Toyota). If it still drives, get it to a hybrid-qualified shop and don't touch any high-voltage parts.

Does P0AA6 mean the hybrid battery is bad?

Not necessarily. Despite the name, Toyota's INF codes show the fault can be in the battery area, the inverter, the motor/generator cables, the transaxle or the electric A/C compressor, and RepairPal lists coolant leaks and wiring first.

What do INF codes 526, 611, 612, 613 and 614 mean?

On Toyota hybrids, 526 is the general isolation fault stored first. On the next trip a specific code points to the area: 611 A/C compressor, 612 HV battery area, 613 transaxle and inverter, 614 high-voltage DC area (Toyota Prius repair manuals).

How much does it cost to fix P0AA6?

None of the sources gives a repair cost. It can range from fixing a coolant leak or cable to replacing an inverter, compressor or battery, so get a diagnosis and a written estimate, and check hybrid warranty coverage first.

Sources

Last reviewed 2026-10-22. Code definitions and repair steps can vary by manufacturer. Confirm with your vehicle's service information.