The Passenger Presence System (PPS) is a calibrated system that requires checking for preloads within each region when the system has been serviced or replaced. If the passenger seat bottom cushion, seat bottom trim, or heater pad has been serviced, reinstalled, or removed for any reason, the procedure below will check for any preloads on the PPS. The PPS module cannot be tested for preload until it is unlocked using SPS programming. A service replacement PPS module does not require an unlock procedure prior to an initial preload test. Once a preload test has been performed, the PPS module will lock regardless of a pass or fail status. If a module needs to be retested, it must first be unlocked with SPS programming. Before you start, read these procedures carefully and completely. For further information regarding the PPS, refer to SIR System Description and Operation.