2009 Toyota Prius 1.8L Other · PJ59 JRV

General underbody corrosion is the recurring mechanical theme across this third-generation Toyota Prius's MOT history, and the most recent test on 10 April 2026 marked the first time the issue was formally noted. The vehicle has now recorded eight consecutive pass certificates dating back to January 2019, so it has remained roadworthy throughout, but the 2026 advisories introduced a new dimension: alongside the now-customary engine cover and under-tray obscuring notes, the tester recorded "general under body rust" and "under components corroded". This is the first appearance of structural-style corrosion language in the record, and for a 2009 Prius that has covered 168,650 miles across seventeen winters of road salt exposure, it warrants close physical inspection rather than dismissal. Prior years had been comparatively clean, with only isolated tyre wear advisories in 2020 and 2024, plus a defective rear exhaust mounting noted in 2020. The trajectory, therefore, is not one of chronic failure but of emerging age-related deterioration on the underside of the vehicle. Usage data is consistent with a working daily driver rather than a low-mileage garage queen. From the 2019 test onwards, the annual mileage accumulation sits at roughly 9,000 to 12,000 miles per year, which is broadly average for a vehicle of this age and type and indicates the car has been in regular service rather than laid up. There are no unusual mileage jumps, no multi-year testing gaps, and no evidence of long stationary periods that would typically promote issues such as brake disc corrosion, dry-rotting of rubber boots, or battery deterioration. For a Prius, this kind of steady annual use is arguably preferable to very low mileage, because the hybrid battery, inverter coolant system, and brake actuators benefit from regular thermal cycling and exercise. The cumulative 168,650 miles does, however, place the conventional powertrain components such as the engine oil pump, e-CVT transmission input damper, and 12V auxiliary battery well into their wear zone. The 2026 underbody corrosion advisories should drive the inspection priorities. On a ramp or over a pit, the buyer should look closely at the front subframe, rear suspension trailing arms, brake and fuel pipework, and the lower edges of the sill and wheel arches for any through-section rust or scaling heavy enough to flake when probed with a screwdriver. Pay particular attention to the rear axle beam mounting points and the front lower control arm bushes, as these are common Prius corrosion hotspots and would manifest on a road test as clonks over speed humps, vagueness through high-speed corners, or uneven tyre wear across the rear axle. The exhaust mounting advisory from 2020 has not reappeared, but a second check of the rear silencer hangers and rubber mountings is worthwhile given the general rust picture. Tyre management is another practical consideration based on the record. The nearside front has worn close to the legal limit on three separate occasions (2020, 2024, and 2026), suggesting either a persistent geometry issue, a worn front suspension component allowing camber drift, or simply an alignment that has never been reset. On a test drive, the car should track straight without steering pull, and any uneven shoulder wear on the existing fronts should prompt a four-wheel alignment check and inspection of the front strut tops, top mounts, and lower arm bushes. Finally, listen for any rising engine RPM without a corresponding speed increase on gentle inclines, which on a Prius can indicate inverter or hybrid battery weakness, and check that the engine starts cleanly even from cold, as the petrol unit typically runs more frequently at this mileage to compensate for any reduction in hybrid system efficiency.