Their customers are the car buyers.Andy
The customers aren't the car buyers, the manufacturer's direct customers are the dealerships. The people that buy the cars don't buy them from the manufacturer, they buy them from the dealer.
I love it when I have the footing to argue with Randy!

I'm not 100% on the Big 3 but I know that the Honda assembly plants' customer is not the end user OR the dealers but American Honda Motor Company, Inc., sort of the parent like. AHMC buys the cars from Honda of America Manufacturing, Inc. and sells them to the dealers.
Who requires GM to be TS certified when they are assembling a car?
GM. The parent company and the final assembly, engine or transmission manufacturing supplier are not necessarily the same thing.
Who is the customer that is specifying the production or service parts for the auto OEM? It could be the dealer.
Or it could be the OEM. It does not say anywhere in the TS, guidance or rules that any of this has to make sense.
The Tier 1 is the direct supply chain to the OEM (and Tier 2 are their suppliers, ....). The OEM's customers (among others) are the franchise dealerships.
In terms of application. ISO TS can apply anywhere in the supply chain. I know one Jaguar site listed supplies bodyshells and painting services to other plants (and is therefore a Tier 1).
I believe some OEMs are obtaining certification to TS to show that it is not a case of "do as I say, not as I do!"
Now we're getting somewhere. Leave it to Paul to make some sense out of this mess!
You are right to question this. Dealerships are what is termed as intermediaries in marketing. They are agents. They help to serve and sell and channel all customer complaints/feedback back to the manufacturer. The end user/purchaser is still the customer.
DCX grades their dealers based on some kind of customer feedback and the ones that make the grade get that "5 Star Rating". I think that this fell apart due to a lack of dealers seeing anything like coherence from the OEM. Honda and Toyota have strict standards on how dealerships look and operate. Auditing and/or controlling your customer, now there's a novel approach (goes off to make list of customers that NEED to be audited and or controlled).
For some strange reason, some OEMs got their subassembly plants certified to TS. Still acceptable. But next they wanted the assembly lines to be certified and the CBs were too happy to oblige. The oversight body has chosen to look the other way.
The reason is not strange. To quote Grandmaster Flash from "The Message": "It's all about money, ain't a
[email protected]#$ thing funny, you got to have a con, in this land of milk and honey.
The assembly plant that assembles Mercedes in Malaysia is not owned by DCX but a DCX subsidiary had some investment in it - and they assembled other brands also (economy of scale).
Check it out. The supplier becomes the OEM. Magna assembles cars for DCX and is looking to buy the Chrysler/Plymouth/Dodge/Jeep portion. I read that Magna has put an enormous amount of due diligence into this and that the price tag is around $5B (a far cry from the $35B soaking that DaimlerBenz took).
We have been told the following but I still can't find acutal proof of the following: "Actually TS requires one to have some customer in the automotive supply chain who demands a TS certification."
Good luck in your quest for "proof".
Are dealers subscribing customers to the OEM? By "OEM", I mean the last point in production - where the car rolls off the assembly line.
Do the dealers "specify parts" to be manufactured?
When was the last time a dealer told a car manufacture what type of car to make?
How many dealers are TS certified?
In answer to your multiple questions:
No,
No,
After Ford made the Edsel, and,
Zero, and I doubt if you will find any dumb enough to
buy pay for an ISO9001 cert, either.