What is the 2006-2019 Toyota Highlander Hybrid Inverter Coolant Pump Failure (Inverter Overheat) — P0A05 / P0A93?

The Highlander Hybrid uses a dedicated electric water pump to circulate coolant through the power inverter/converter, which runs separately from the engine cooling system. The electric pump wears out and stops circulating coolant, allowing the inverter and hybrid electronics to o… Repairs typically run $700-$1,100. Severity: high.

What is the 2006-2013 Toyota Highlander Hybrid Brake Booster / ABS Actuator Assembly Failure (Accumulator Leak) — C1391?

The regenerative-braking brake actuator (the integrated ABS/booster/accumulator pump module) is a known weak spot on the Highlander Hybrid. The accumulator develops an internal leak and the pump runs constantly, triggering a loud, repetitive whirring/buzzing and warning lights; i… Repairs typically run $1,600-$3,500. Severity: high.

What is the 2001-2007 Toyota Highlander V6 Engine Oil Sludge / Gelling (1MZ-FE / 3MZ-FE) — Oil Pump Pickup Starvation?

The early Highlander 3.0L 1MZ-FE (and successor 3.3L 3MZ-FE) V6 is prone to engine oil sludge/gelling. Blow-by gases and moisture that fail to burn off (aggravated by short-trip driving, extended oil intervals and a PCV valve that clogs) turn the oil to a gel that coats the valve… Repairs typically run $500-$6,000. Severity: high.

What is the 2001-2016 Toyota Highlander Catalytic Converter Efficiency Failure — P0420 / P0430 Check Engine Light?

A very common Highlander check-engine complaint is P0420 (Catalyst Efficiency Below Threshold, Bank 1) and its Bank 2 twin P0430. The downstream oxygen sensor readings track the upstream sensor too closely, indicating the catalytic converter is no longer scrubbing exhaust efficie… Repairs typically run $200-$2,500. Severity: medium.

Toyota · Known Issues

2006 Toyota Highlander Problems: 7 Issues Every Owner Should Know

2006 model year · 1,200+ owner reports · Updated July 2026

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According to Au7o's analysis of 1,200+ owner reports, the 2006 Toyota Highlander has 7 documented known issues, with 6 rated critical. The most serious are Hybrid Battery Pack Degradation and Failure ($1,500-$5,500 repair), 2.4L 2AZ-FE Head Gasket and Head Bolt Thread Failure ($2,500-$5,000 repair), Hybrid Inverter Coolant Pump Failure (Inverter Overheat) — P0A05 / P0A93 ($700-$1,100 repair), Hybrid Brake Booster / ABS Actuator Assembly Failure (Accumulator Leak) — C1391 ($1,600-$3,500 repair), Radiator Internal Transmission-Cooler Failure — ATF/Coolant Cross-Contamination ("Strawberry Milkshake") ($400-$4,500 repair) and V6 Engine Oil Sludge / Gelling (1MZ-FE / 3MZ-FE) — Oil Pump Pickup Starvation ($500-$6,000 repair). The most commonly reported issue is Hybrid Battery Pack Degradation and Failure with 1,200 owner reports. Across all issues with published estimates, repair costs range from $200 to $6,000. DIY maintenance guides at .

All 7 Known Issues

Frequently Asked Questions

What are the most common Toyota Highlander problems?

According to Au7o's analysis of 1,200+ owner reports, the 2006 Toyota Highlander has 7 documented issues. The most frequently reported are: Hybrid Battery Pack Degradation and Failure, 2.4L 2AZ-FE Head Gasket and Head Bolt Thread Failure, Hybrid Inverter Coolant Pump Failure (Inverter Overheat) — P0A05 / P0A93. Of these, 6 are rated critical and should be addressed promptly.

Is the Toyota Highlander reliable?

The 2006 Toyota Highlander has 7 known issues documented across 1,200+ owner reports. 6 issues are rated critical: Hybrid Battery Pack Degradation and Failure and 2.4L 2AZ-FE Head Gasket and Head Bolt Thread Failure and Hybrid Inverter Coolant Pump Failure (Inverter Overheat) — P0A05 / P0A93 and Hybrid Brake Booster / ABS Actuator Assembly Failure (Accumulator Leak) — C1391 and Radiator Internal Transmission-Cooler Failure — ATF/Coolant Cross-Contamination ("Strawberry Milkshake") and V6 Engine Oil Sludge / Gelling (1MZ-FE / 3MZ-FE) — Oil Pump Pickup Starvation. Prospective buyers should inspect for these issues and factor potential repair costs into their purchase decision. Regular maintenance following the manufacturer's schedule helps prevent many common problems.

How much does it cost to fix common Toyota Highlander problems?

Repair costs for known Toyota Highlander issues range from $200 to $6,000, depending on the specific problem and whether you choose DIY or professional repair. The most critical issue, Hybrid Battery Pack Degradation and Failure, typically costs $1,500-$5,500 to repair. Au7o provides step-by-step DIY maintenance guides that can help reduce repair costs.

What is the 2006-2013 Toyota Highlander Hybrid Battery Pack Degradation and Failure?

Highlander Hybrid NiMH battery packs degrade over time, with individual cells failing after 8-12 years or 150,000+ miles. Failed cells cause reduced fuel economy, loss of hybrid assist, and eventual inability to start the vehicle. Repairs typically run $1,500-$5,500. Severity: high.

All 7 Known Issues

2001-2007 Toyota Highlander: 2.4L 2AZ-FE Head Gasket and Head Bolt Thread Failure#

2001-2007 Toyota Highlander: V6 Engine Oil Sludge / Gelling (1MZ-FE / 3MZ-FE) — Oil Pump Pickup Starvation#

2006-2019 Toyota Highlander: Hybrid Inverter Coolant Pump Failure (Inverter Overheat) — P0A05 / P0A93#

2001-2013 Toyota Highlander: Radiator Internal Transmission-Cooler Failure — ATF/Coolant Cross-Contamination ("Strawberry Milkshake")#

2006-2013 Toyota Highlander: Hybrid Battery Pack Degradation and Failure#

2006-2013 Toyota Highlander: Hybrid Brake Booster / ABS Actuator Assembly Failure (Accumulator Leak) — C1391#

2001-2016 Toyota Highlander: Catalytic Converter Efficiency Failure — P0420 / P0430 Check Engine Light#

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