When I was looking to buy this car, the Check Engine light was on. The previous owner said Toyota told him it was code P0420 which meant the Catalytic needed replacing. He didn't do it as the cost was over $500 and he said the car ran OK. I asked if I could get a pre-purchase inspection before I bought it.

I checked a few web sites regarding the P0420 code and came across that it isn't usually the Catalytic. I brought it to Toyota and asked the Mechanic to check exhaust emissions after the Catalytic. He did and said it seemed good. He suggested to start by replacing the Oxygen (O2) sensor after the Catalytic to see if that solved the engine light problem. Everything else was good or just needed maintenance stuff ( ...filters, etc...). So I decided to buy the car and try and fix the Engine light issue.

Toyota's cost for the O2 sensor was $285 + ~$100 install. I bought the sensor through a Mechanic friend wholesale for about $160 and took about 3 hours to install it myself (I took my time ). It needed some wd40 to loosen the old sensor from the rusted exhaust, but then it was pretty straight forward. I then reset the computer by disconnecting the battery for about a minute.

It's now been about 3 months and the light has not come back on. Anyone else who gets the P0420 code, don't rush out to replace the Catalytic. I think the computer is not specific enough to pinpoint the problem, so you need do some old fashioned trouble shooting first.

The car now runs great. Toyota makes a good engine, so don't let the engine light scare you from buying or keeping the car.

Good Luck .... Davy

My mechanic, who's judgment I trust, tells me that the reason my Check Engine light is on is that my car's catalytic converter sensor is faulty. He says the converter is operating properly.

He called Toyota regarding a fix - and their suggestion was to replace both the sensor and the computer it feeds. He tells me that will run in excess of $1,000 and recommends against doing so. Apparently, the warranty on that system ran out at 80,000 miles, so any fix is on my nickel.

I have no problem with the car as-is (although I would like the Check Engine light is effectively useless), but a buyer will doubtless be concerned about the problem. I know I would be if I were buying the car.

I'm wondering if I'm alone in experiencing this problem - and if anyone has a fix that's a tad more affordable than $1,000.

Update from Mar 7, 2010: My mechanic, who's judgment I trust, tells me that the reason my Check Engine light is on is that my car's catalytic converter sensor is faulty. He says the converter is operating properly.

He called Toyota regarding a fix - and their suggestion was to replace both the sensor and the computer it feeds. He tells me that will run in excess of $1,000 and recommends against doing so. Apparently, the warranty on that system ran out at 80,000 miles, so any fix is on my nickel.

I have no problem with the car as-is (although constantly-illuminated Check Engine light is effectively useless), but a buyer will doubtless be concerned about the problem. I know I would be if I were buying the car.

I'm wondering if I'm alone in experiencing this problem - and if anyone has a fix that's a tad more affordable than $1,000.