When we bought our 2001 Toyota Sienna in 2011 the check engine light was off. But on the way home from the dealer the light came on. We came to know that the van had a long history regarding that code. I guess the dealer had reset the computer before we did the test drive. I guess that's why they say to bring used cars to a mechanic for inspection. I didn't know anything about OBD (on-board diagnostics) at the time. Learned a lot since then.
It was a long road to fixing the problem because I had to learn a lot along the way. The things I tried:
1. Bought an OBD reader and reset the computer then took it in for emissions test. Haha, yeah, nice try. They can't test the car if the tests read 'not ready'.
2. There was a Toyota bulletin out about how there was a known problem with the ECU:
Technical Service BULLETIN October 19, 2005 "M.I.L. “ON” DTC P0420 – EG047-05"
So I got a good deal on the computer from Gary at Toyota of Newnan: http://www.toyotaofnewnan.com/Department-Parts.aspx.
Unfortunately that didn't fix the problem.
3. I could see in the vehicle history reports that one shop had recommended the computer replacement (~$1500) and another had recommended replacing the catalytic converter and O2 sensor (~$2000)!
So I took the van to the local Toyota dealer to see what they recommended. For $65 they tested and suggested I replace the catalytic converter and O2 sensor. Estimate for repair about $2500 including tax. Yipes!
So I reviewed my Haynes book, found online Toyota maintenance manual (image below) and did research on the internet to see how to replace the CAT. I could purchase both warm up three-way catalytic converters (WU-TWC) and the catalytic converter itself for about $900 so that could be big savings.
I worked up the courage to try the replacement myself and ordered the parts from www.autopartswarehouse.com with only a few weeks to spare before we had to pass the emissions test in order to keep the registration current.
The parts arrived within a couple weeks and the gaskets were included, so I didn't need the ones I had purchased from the local www.oreillyauto.com store.
One tip: be very careful when ordering the exhaust pipes - some may be listed as 'direct fit' but will also have text indicating that some minor welding will be required. I couldn't use the bank two WU-TWC pipe because it needed welding/modification. Here's the two pipes I did replace. Notice that the new pipe in front on the left is much more basic that the OEM part on the right:
But not being able to use that third pipe saved me $350 actually because replacing just these two pipes above (the bank 1 WU-TWC and TWC), plus the O2 sensor did the trick!
Summary
If I could do this over again, I would:
1. Replace just the TWC pipe and see if that alone fixes the problem. ~$250
- I used autopartswarehouse.com Eastern Catalytic Converter part number EAST40432
2. If not, I'd then replace the post-cat O2 sensor also and see if that fixes the problem. ~$100
- I bought that at the local O'Reilly
Note: when replacing the O2 sensor
you do not need to remove the passenger seat. Just unscrew the left-side plastic panel around the base of the front passenger seat. That gave me enough access to unclip the original O2 sensor wire and clip in the new one. Saved a lot of time!
You might be able to go even cheaper if you have welding equipment. You could hacksaw the old TWC out and weld in a generic replacement. The generics appear to be about $100.
I drove the van up onto ramps and large flat bricks to make room to work underneath. Please be super safe about that. I was on a concrete pad so it was pretty solid.
Here's what the old O2 sensor looked like. It may still have been working ok, I didn't have time to check.
Hope that helps someone!
