I can't help with your problem, except to say that the dealer would have records under your friend's name for what parts they sold him, and what services they performed on the vehicle. I would verify all of this. The parts guys sometimes make mistakes that DIYers don't catch.

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1996 C280 289K Traded
1997 E420 167K Traded
2001 S430 240K Traded
2010 E550 4matic 80K
2000 GMC Jimmy 198K Gone to Boneyard
2003 Camry LE 196K
2011 Mazda3 i Sport 31K