Toyota Prius vs Toyota Aqua: known faults compared
Toyota’s two best-known hybrids. The Prius is the larger car; the Aqua uses a smaller version of the same hybrid system.
The catalogue documents 42 faults for the Toyota Prius and 20 for the Toyota Aqua. That is a measure of how much has been recorded, which grows with how many were sold and for how long, not a reliability score.
At a glance
| Measure | Toyota Prius | Toyota Aqua |
|---|---|---|
| Documented faults | 42 | 20 |
| Rated major or critical | 36 | 14 |
| Rated common or very common | 22 | 16 |
| Typical repair | $420–$1,100 | $300–$950 |
| Model years covered | 2003–2023 | 2011–2021 |
| Fuel types with documented faults | hybrid | hybrid |
| Service schedule on the model page | Yes | Yes |
Where the Toyota Prius goes wrong
Most likely to turn up
- Traction Battery Cooling Fan Blockage
- Headlight Projector UV Discolouration
- 12V auxiliary battery in the boot - small, weak and often neglected
Most expensive to fix
Where the Toyota Aqua goes wrong
Most likely to turn up
- Hybrid traction battery cell degradation and failure
- Front Lower Control Arm Bush Deterioration
- Rear Brake Corrosion from Regenerative Braking Bias
Most expensive to fix
Where the Toyota Prius and Toyota Aqua differ
- Electrical: 15 documented on the Toyota Prius, 5 on the Toyota Aqua. The costliest on the Toyota Prius is PHV Lithium-Ion Traction Battery Capacity Degradation, at up to $8,500.
- Cooling: 6 documented on the Toyota Prius, 2 on the Toyota Aqua. The costliest on the Toyota Prius is PHV/Prime HV Battery Liquid Cooling Pump Failure (ZVW52), at up to $2,800.
- Engine: 5 documented on the Toyota Prius, 1 on the Toyota Aqua. The costliest on the Toyota Prius is Head gasket failure driven by EGR system carbon clogging (1.8 2ZR-FXE), at up to $5,500.
Both carry several documented faults in electrical, brakes and suspension, so check those areas on either car.
Fault areas side by side
| Area | Toyota Prius | Toyota Aqua |
|---|---|---|
| Electrical | 15 | 5 |
| Brakes | 5 | 4 |
| Cooling | 6 | 2 |
| Suspension | 3 | 5 |
| Engine | 5 | 1 |
| Transmission | 2 | 2 |
| Body & Rust | 4 | 0 |
| Fluid Leaks | 1 | 1 |
| Interior | 1 | 0 |
How to read this comparison
These are documented faults, not failure rates. A car sold in bigger numbers, for more years, has more written about it. Neither list tells you about the car in front of you: that depends on its history and how it has been looked after. Use the lists to know what to check, then check it.
Checking one of these cars?
Type the plate for the free basics and the faults that apply to that exact car. The full history and the guided inspection are one-off paid checks, no subscription.
Questions
Which has more known problems, the Toyota Prius or the Toyota Aqua?
The catalogue documents 42 faults for the Toyota Prius and 20 for the Toyota Aqua. That is a measure of how much has been recorded, which grows with how many were sold and for how long, not a reliability score. Of those, 36 on the Toyota Prius and 14 on the Toyota Aqua are rated major or critical. What matters more is whether the car in front of you has the specific faults its model is known for.
Which is cheaper to fix?
A typical documented repair runs $420 to $1,100 on the Toyota Prius and $300 to $950 on the Toyota Aqua, at New Zealand independent workshop rates. The expensive exceptions are listed on this page for each car, and they are the ones to check for before you buy.
What is the most expensive known fault on each?
On the Toyota Prius it is MG2 Resolver Fault P3190 Hybrid Transaxle Failure, documented at up to $8,500. On the Toyota Aqua it is MG1 Resolver Fault Causing Traction Battery Warning, documented at up to $6,500.