Faru - I guess I can see this both ways. There was an instance in my past where I took (in this case it was my Dodge Ram, when it had warranty coverage) to a dealer. But before I did, I diagnosed that the lift pump (a fuel pump), would experience large instances in time where it would just NOT pump (and the truck would stall). I put a fuel pressure gauge on the fuel line just post lift pump and duct taped the gauge to my windshield, and I watched the pressure. This lift pump problem was / is a known issue.
I knew up front the stealership was going to harass me about, "we have to diagnose, and that's $90, but that's refunded if it is a warranted repair." And, "we have to scan your codes and blah blah blah." But I also knew, the failed lift pump produced no codes, as well as there was an ECU flash they did automatically to unsuspecting customers, that I didn't want done ... because that flash dumbed down various gauges (long story).
So before I went, I backed the OBD connector out of its mount and pushed it up behind the dash into a rat's nest of wiring. I left the gauge taped to the windshield (outside) take it to the dealer, roll into the service bay, "How can we help you sir?" I say, the lift pump has failed, please replace it.
And off to the races they go with their crap. I said to the guy again, "the lift pump has failed, please replace it." And added context, "The failed lift pump can be verified by the gauge taped to the windshield." The service writer says, well, we have still have to check the codes and diagnose, it'll be $90 to diagnose at minimum, unless it's covered. I just said blankly again, "the lift pump has failed, please replace it." He repeated the, "we'll have to scan the codes."
I held the keys out and said, "good luck with that." He looked perplexed and I left. A different service guy called me a couple hours later and said, your new lift pump is in and your truck is ready. I asked them how much, he said, no charge, it's covered under warranty.
I went back and walked up to the original service writer. He looked totally miffed, handed me my keys and service document and didn't say a word. Neither did I. I still wonder how long they spent trying to find that connector. When I got home, it took me about 30 minutes to find it myself, and I knew where I had pushed it! But got it and snapped it back in it's mount. There was no write up on the receipt about having scanned the codes or diagnosis. Just something like, "replaced failed lift pump."
The point is, I was 100% certain I had identified the problem, and went prepared.
You'll have to splain to us how your brother diagnosed this. I don't "know" the structure of the engine in the area of the timing belt, but I would imagine there's a cover. But from memory (of other cars), that cover is not a simple affair to remove.
And lastly, regardless of what the problem is, timing chain or other, if you are not the original owner and thusly have no warranty coverage (which I think is the case), then my recommendation is to use a private mechanic. As every OEM dealership in the U.S. sucks be stanky crust-covered ass. They're either really nice to their customers, and do shi11y work, or they're a-holes and do shi11y work.
Furthermore, I have had really good luck asking for recommendations for fair priced, quality autowork on facebutt. Stuck to the recommendations and do now have one particular shop that does really good work on the stuff that I don't want to do, and he does it at fair costs. Smart guy too, so glad I found the guy.
View my fuel log 2020 Mirage ES 1.2 manual: 42.4 mpg (US) ... 18.0 km/L ... 5.6 L/100 km ... 50.9 mpg (Imp)