IsItAGoodCar
Reliability Guide

Common Problems with the
2004 Toyota Prius Mk2 (XW20)

Launch of the second-generation Toyota Prius (XW20) in the UK, introducing the refined Hybrid Synergy Drive with a 1.5-litre Atkinson-cycle petrol engine, 50 kW electric motor, aerodynamic liftback packaging (0.26 Cd), and full exemption from the London Congestion Charge.

What changed for 2004

  • •Second-generation Hybrid Synergy Drive with 50 kW electric motor and 201.6V NiMH battery
  • •Aerodynamic liftback five-door bodystyle achieving 0.26 drag coefficient
  • •By-wire electronic braking system with regenerative energy capture
  • •Standard keyless Smart Entry and multifunction dashboard touchscreen

Common MOT watch-outs

  • !Rear brake disc surface corrosion and pitting from regenerative braking underuse
  • !Front suspension anti-roll bar drop link ball joint play from urban speed humps
  • !Headlamp aim misalignment from aged plastic lens mounting clips
3
Known Issues
1
Serious
2
Moderate
0
Minor

All Known Issues

High-Voltage Traction Battery Degradation and Cell Imbalance

SeriousElectrics & Electronics

The 201.6V nickel-metal hydride (NiMH) high-voltage traction battery pack deteriorates over time and extended mileage. Individual battery modules lose capacity and develop voltage imbalances, causing the hybrid control module to illuminate the master warning triangle and store DTC P0A80. In heavily congested UK city driving, degraded packs force the petrol engine to run continuously, drastically harming fuel economy and accelerating wear on the engine.

Est. Repair Cost: £600–£1,400
Warning Signs:

Petrol engine runs almost continuously even when idling at warm operating temperature, Battery state of charge display on centre screen fluctuates rapidly between empty and full bars, Red master warning triangle illuminated on instrument panel with check hybrid system warning, Noticeable reduction in acceleration performance and loss of EV electric driving mode

What to Inspect:
  • Monitor the battery state-of-charge display during a 15-minute mixed test drive to verify progressive charge and discharge
  • Confirm the petrol engine cuts out smoothly when coming to a halt at traffic lights once warm
  • Scan the OBD-II diagnostics port for hybrid control codes P0A80 or P3000
  • Examine service history documentation for hybrid battery reconditioning invoices or Toyota health checks
Verified by IsItAGoodCar Research TeamUpdated

Electric Inverter Coolant Water Pump Failure

ModerateCooling System

The dedicated electric auxiliary coolant pump responsible for circulating coolant through the hybrid power inverter assembly can fail internally due to electrical coil burnout or impeller seizure. When circulation stops, inverter temperature rises rapidly under load, triggering the red triangle master warning light, storing DTC P0A93, and forcing the car into fail-safe limp mode to prevent inverter failure. Subject to UK safety recall R/2012/127.

Est. Repair Cost: £180–£350
Warning Signs:

Red master warning triangle and amber engine malfunction indicator lamp on dash, Vehicle enters reduced-power limp-home mode during motorway driving or sustained hill climbs, Lack of fluid turbulence visible in the smaller inverter coolant reservoir when vehicle is switched to Ready mode, Excessive heat radiating from the silver aluminium hybrid inverter casing under the bonnet

What to Inspect:
  • Switch the car into Ready mode, remove the inverter expansion tank cap, and check for active swirling coolant flow
  • Check the DVSA vehicle recall database online to ensure recall campaign R/2012/127 was completed
  • Listen for high-pitched whining or silence from the electric pump mounted beneath the nearside headlight
Verified by IsItAGoodCar Research TeamUpdated
Official Recalls & Reference Documents:

Digital Combination Meter Instrument Cluster Display Failure

ModerateElectrics & Electronics

The central digital combination meter display mounted under the windscreen frequently fails to power on, particularly during damp or cold UK winter mornings. The fault is caused by deteriorated surface-mount micro-capacitors on the instrument cluster circuit board, which fail to supply regulated voltage. When blank, the driver loses the speedometer, fuel level gauge, and gear position indicator, representing an automatic UK MOT failure and preventing the car from shutting down easily.

Est. Repair Cost: £150–£350
Warning Signs:

Digital speedometer and fuel gauge display remain completely black upon pressing the Power button, Vehicle requires pressing and holding the Power button for several seconds before shutting down, Reversing camera image remains displayed on the centre console screen when driving forwards, Air conditioning controls on the multifunction steering wheel become unresponsive

What to Inspect:
  • Power up the vehicle from cold and verify that the digital speedometer illuminates instantly without flickering
  • Power down and restart the vehicle three times in succession to confirm consistent display initialization
  • Check UK MOT history for previous failure notices regarding inoperative speedometer
Verified by IsItAGoodCar Research TeamUpdated

Buying Tips for 2004 Toyota Prius Mk2 (XW20)

  • Verify the high-voltage battery state of charge cycles normally on a 15-minute test drive
  • Check that the petrol engine shuts down cleanly when stopping at operating temperature
  • Inspect the inverter coolant reservoir to confirm fluid circulation in Ready mode
2005
Check a 2004 Toyota Prius Mk2 (XW20) by Registration