Checking for air leakage in the exhaust system (1999): Check

Fig 1: Checking Exhaust System For Leaks Between Cylinder Head & Rear Heated Oxygen Sensor

Courtesy of VOLVO CARS OF NORTH AMERICA.

Check the exhaust system. Spray a soap solution on all joints and connections between the cylinder head and the rear heated oxygen sensor (HO2S).

Only very small and slow bubbles are permissible.