audi a6 2.7tdi starting issues

I need your help with an audi a6 2.7tdi.the issue is like when you switch to ignition the glow plug light will stay on and the engine wont crank.but if i try switching the key to ignition to on and off couple of times the glow plug light goes off and it starts perfect! i got the codes read as no communication with the ecm.After i get the engine started there are no fault codes.pls help
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Hey anuplazar! For our info, what year is your A6?

At first glance, this kinda sounds like an ignition switch problem to me. What does the check engine light do while the vehicle isn't cranking? Before going too much deeper, I'd be tempted to wiggle the key or tap on the steering column while the no communication issue is taking place.

It’s 2011 model Audi A6 2.7tdi .The engine light comes on n goes off when I try to crank.only the glow plug light stays on .

See if your missing power or ground to the engine ECU when it won't communicate