Intake air sensor (688): Location:

4-cyl petrol:  on the charge air pipe

Fig 1: Identifying Intake Air Sensor (688) 4-Cyl Petrol

Courtesy of SAAB-SCANIA OF AMERICA, INC.

4-cyl diesel:  on throttle body

Fig 2: Identifying Intake Air Sensor (688) 4-Cyl Diesel

Courtesy of SAAB-SCANIA OF AMERICA, INC.