CUSTOMER CONCERN The vehicle intermittently will not enter Ready to Drive mode and may not engage reverse when Ready, with multiple powertrain DTCs stored. CAUSE Cooling-system pressure testing confirmed coolant leakage from the upper high-voltage battery assembly. CORRECTION Remove and replace the upper high-voltage battery assembly, program the replacement battery, refill and bleed the electric-powertrain cooling system, clear the DTCs, and verify Ready mode and reverse ope