The engine to chasis grounding cable should measure no resistance as you pointed out. I hope that's what you meant. You will not be able to start the car without that ground cable connected. I dare you to disconnect it and try starting the engine.
When I put together the drive train of my 95 after removal two years ago. I attempted to start the car without connecting that cable. I simply forgot. Smoke came out of the engine compartment. I think I made the same mistake years ago on a 86 325es. Same smoke resulted.
'01 540it, 6/01
'03 325i 5 speed, 9/02
'10 535ix. 9/09
'10 mini 6 speed
'15 mini countryman 6 speed