Vehicle: 2007 BMW 760Li (E66), V12-6.0L (N73TU), Automatic Transmission

Mileage: 128,554

Problem: The vehicle owner asked the shop to replace the coolant and thermostat using the aftermarket part he provided. The technician installed the thermostat and replaced the coolant, but after the job was completed, the engine became hard to start and the malfunction indicator light (MIL) came on.

Details: When the technician connected the scan tool, he retrieved the following diagnostic trouble codes (DTCs):

• 2B5C - P0335 - DME2: Crankshaft Sensor signal
• 2D0F - P0100 - DME2: Air-mass Sensor, Bank 2 signal
• 2EF5 - P0598 - DME: Map Thermostat activation
• 2A80 - P2088 - DME2: Inlet VANOS Bank 2 activation
• 2A85 - P2090 - DME2: Exhaust VANOS Bank 2 activation
• 2D14 - P113B - 2D14 Engine Electronics Air-mass Sensor Correction Signal

The technician rechecked all his work and everything seemed to be fine. He called ALLDATA Tech-Assist for advice. The Tech-Assist consultant told the technician that there had been many reports of problems using aftermarket thermostats on these vehicles, which included hard starting, extended engine cranking times, and blown fuses.

The consultant suggested disconnecting the thermostat electrical connector, clearing the DTCs and see which DTCs reset or change. He also advised to verify that fuse 006 in the integrated supply module, located at the right rear of the engine compartment, was okay.

The technician checked fuse 006 and it was open. He installed another fuse and it popped immediately. When he connected the old thermostat, the fuse did not pop.

Confirmed Repair: The tech ordered a new thermostat from BMW and installed it. As it turned out, the aftermarket thermostat was causing the multiple DTCs, the hard start and fuse 006 to blow. After the repairs, the engine started and ran normally, fuse 006 was fine, the DTCs were cleared and they did not return. Fixed!