Fault-tracing information

Condition 

Fig 1: Identifying Backup Lamps

Courtesy of VOLVO CARS OF NORTH AMERICA.

• Diagnostic trouble codes (DTCs) missing.

Possible Source 

• open-circuit in signal cable from back-up (reversing) lamp switch/gear-shift position sensor.
• Short-circuit to ground or voltage signal cable from back-up (reversing) lamp switch/gear-shift position sensor.
• Contact resistance in terminals.