I have a 2000 4 runner that has now had 2 catalytic converters, and all the accompanying exhaust work, installed due to a check engine light diagnostic, 2 times in the space of 5 years. I have owned the car for 10 years and have put 140k miles on it. I have no idea if the factory installed catalytic converter was on it when I purchased it (I purchased it used from a dealership I use for maintenance). The first install was at 135k miles and now 5 years later at 185K miles the light came on again and the dealership replaced the catalytic converter and all the exhaust stuff again (very expensive)…does this seem reasonable? The car is driven on the highway and around town, no unusual driving or weather conditions. any insight would be greatly appreciated.
More likely it’s the downstream oxygen sensors going bad. When that happens, the computer doesn’t know whether the sensor is bad or the cat itself is bad. Some mechanics don’t bother to diagnose, they just replace the cat AND the sensor, and charge big bucks for it.
So the first question you have to answer is, was the original problem with the cats themselves or with the sensors? My bet is on the sensors.
Stop going to this ripoff dealer and find a recommended local mechanic you can trust.
Do you have to add oil to the high mileage engine between oil changes?
If so, oil burning can contaminate the catalytic converter as the vehicle is driven causing the converter to become ineffective.