I agree that it is a good idea, but specifically I'm trying to find out if Toyota recommends or requires that you do in any official documentation.

I had a shop do my TB a few months ago, and it threw a CEL right when I picked it up. I took it back, they checked the timing again and told me it was off by a tooth, and fixed it. 2 days later, CEL again. I took it back, and the code was inactive and didn't come back after they cleared it. 10 days later, CEL again. They took the front end off for the third time, said the timing and sensors checked out ok so they've done all they can, it must be a bad ECU, which I'd have to take to the dealer to get replaced.

I got a second opinion and the second shop found it off by a tooth on each cam. He didn't see anything wrong with the part, but given the history, he recommended replacing the tensioner also, which I agreed with. So either the first shop was incompetent and set the timing wrong twice, or the tensioner was bad and let it jump repeatedly.

I'd like to know what Toyota officially recommends or requires replacing when doing the timing belt, so that I can determine if the first shop blatantly missed a step and should be held accountable, or just did poor troubleshooting after the fact and is arguably less accountable. I've looked in various service manuals and haven't found anything specific. Can anyone share a link or pdf to that?

Thanks,
Todd

I'm not sure what Toyota recommends...but whenever I did a timing belt I ALWAYS replaced the tensioner. It's just prudent to replace it since you're already in there replacing the belt.

You should replace the tensioner, but it is a preventive replacement unless your current tensioner has failed. It sounds like in your case that the first shop didn't do their job. Your tensioner was working fine with your old belt. It is highly unlikely that two cams were off one tooth because of a bad tensioner. It would have jumped a lot more from a bad tensioner. Most likely they didn't have the belt tight when they pulled the pin to release the tensioner and it skipped. That is very easy to do when you only have two hand and you are trying to keep a stiff belt lined up perfectly on 3 marks and pull a pin to release the tensioner.