an Exhaust recycle hose cracked; causing cabin to fill with carbon dioxide. Driver, (me) became disorented.. ran off right shoulder, ran into center divider cement, before rearending truck. Engine light later came on indicating (HVOC?) ERROR Mechanic was able to locate leak and repair. Vehicle now performing properly. A DEFECT THAT ALLOWS CARBON DIOXIDE INTO THE PASSENGER CABIN, IS A SERIOUS AND LIFE THREATENING SITUATION.