I found Dinan through Yelp and mentioned to be good at forums. My E90 M3 had just started intermittently (sometimes after 1min, sometimes after 2 hours) throw itself into limp home mode and complain at DCS (and a few other things). I saw that Dinan offered free fault code reading, so I went there.
The guy helping me was nice and fun, but the first thing he said was that maybe I should renovate my engine for several $thousand as he said the early s65 engines had too small tolerances in their rod bearings. He took me through a tour and showed me some bad bearings and informed me that it will be more expensive later and asked if I wanted this renovation. I don't think he tried to fool me, but they should have much more on their feet before trying so hard to sell something so expensive: verified statistics with high %age of engines that had malfunction due to this, or a BMW recall.
It felt really bad, like my car was a piece of crap. Reading on the web (as he suggested) conveyed a very different story with very few confirmed such issues. Maybe 0 if one does not count modified cars (turbos etc)
Next thing he told me they would charge $155 to check what was wrong with my car. I expected a fault code read at $0. I would really like to see that they offer that code check as mentioned at their website. I felt cheated, but did not want to argue. On top of that, they did not guarantee that they will find the fault, they only say they will look for errors one hour. This I really don't like. I expect to get a diagnose at a fixed price.
After an hour the mechanic came back. He said they could not find the reason for the DSC error, after performing some related checks. Partly due to plenty of fault codes. He made it sound as if I had plenty to fix, which made me feel bad again. At least some of those codes did not make sense since the car had run perfectly except the last week. I suggested that it maybe was due to that I had emptied my battery which made the computers do a bunch of strange things including reprogram/reset itself (verified). He said it is possible. They reset the fault codes in order to more easily find what was really wrong. It was unclear how much the rest of the diagnosis was going to cost me, which felt very bad.
He agreed to read fault codes for free after coming back wen the DCS light came on again. I took the car on a full day drive. Several times I got various issues but always the DSC light. Coming back and after reading the fault codes, it was clear that the only fault codes where related to the throttle actuator in bank 2 (out of 2). He said that I should change both, gave me a price at about 3000USD including 6.5 hours of labor for the repair and asked if he should schedule it. I said I have to think about it. He gave another proposal at about 2000USD where we only change the one that was broken. I said I have to think about it. Reading on the web showed that this is a very common problem with the S65 and S85 engines around 60k miles, and the culprit is wear of the teeth of a plastic cogwheels (that cost probably 5 USD). So he is right on one thing: you should change both once one is failing, because the wear is almost the same, and the work to change one or two is almost the same. What annoyed me was that a plastic piece at a few dollars would cost me 3000USD ! That day I did not like BMW engineers.
Reading on the web it is clear that Dinan and other workshops over charge. The time for an amateur to change the actuators the first time he does it is much less than what Dinan is quoting! Especially since Dinan sais they change these all the time, I expect them to be much faster than an amateur !
And most disappointing regarding the Dinan experience is that they did not tell me that this is actually under warranty!!! I was LUCKY that I studied the web enough hours on this problem to see that this is covered by the BMW Californian Emission warranty mentioned in the service booklet, which explicitly states that it includes throttle actuators. To have a service shop in California and not be aware of this is unforgivable! All their exchanged throttle actuators should have been replaced for free!
Anyway, I took my car to the badly reputed BMW dealer and got nothing but good service. 0USD including a new diagnosis, shuttle service, no up sales, repaired car washed and vacuumed.
Finally, I must recommend to go to the dealer for unknown issues since you will blow 155USD on diagnosis for warranty issues since Dinan can't do such warranty jobs. And even worse: they might not tell you it is a warranty issue and you can blow 3000USD as I would have done !
If you are outside the mandatory 7years70kMiles warranty, study the web. There are instructions on how to do this yourself at about 3 hours of work with refurbished parts from ebay at a cost of 600USD for both. Or if you can make a cogwheel,
My car has since behaved as always before: perfectly with german precision, not even ever a single misfire read more