I'm not sure if this is the right forum, but it is general enough of a question I hope it can be addressed (and be helpful) here.

I recently got the diagonal half-engine symbol as a warning light. A trip to the auto parts store showed it as P054B, which is pretty generic, usually involving the valve train or turbo. However, it offered the additional detail as "valve timing solenoid" w/o specifying intake or exhaust.

I went to the dealer, coughed up $150 for their "diagnostic service" and it also showed valve timing solenoid, but specified the exhaust.

So, I'm wondering more broadly if the aftermarket OBD-IIs you can buy (or the auto parts store service) will never get as detailed as you the diagnostics at the dealer and will not sufficiently identify the fault.

Does anyone know for a fact (not anecdote, please) whether the aftermarket readers are are discrete as the dealer's in identifying the actual fault?

Thanks for any help on this. These Coopers spit out trouble codes like watermelon seeds, so these diagnostic fees start to add up.

 

This, i have one for both my MINIs. Its gives you a bunch of info. Those generic readers cant find most of the stuff.

https://www.ecstuning.com/b-schwaben...020sch01a~scf/