2006 A4, 2.0 tdi, 100K miles. Driving at 75 mph. Engine stuttered once lost power then died. Coasted to a stop, battery was too low to crank. Towed home, charged battery. Cranks but no fire, won’t start. Oil level ok, water ok. No cross contamination of oil/water. The only code is for #4 glow plug. No unusual engine noise or idiot lights before it died. Timing belt is ok. All fuses are good including the ones by the computer. Looking for suggestions.