Circuit Description

WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

The passenger presence system (PPS) monitors itself for faults and will set flash diagnostic trouble codes if a fault is detected. The PPS communicates with the inflatable restraint sensing and diagnostic module (SDM) via non class 2 communications. When the SDM receives input from the PPS that a PPS fault has occurred, the SDM will request the instrument panel cluster (IPC) to turn the AIR BAG indicator located on the IPC ON. To determine what diagnostic trouble codes (DTCs) have been set by the PPS, the Tech 2 is used to command the SDM to request the PPS to flash the DTCs using the PASSENGER AIR BAG ON/OFF indicators located on the rearview mirror. The Tech 2 sends a string of commands to the SDM that allows the SDM to communicate with the PPS module and initiate the flashing of the DTCs. When the Tech 2 has completed sending the commands, the PPS will begin flashing any current or history DTCs that the system has stored. When the SDM no longer receives commands from the Tech 2, the SDM mistakes this as a communication fault and sets DTC U1241. DTC U1241 will set when the Tech 2 is used to flash DTCs from the PPS or after the PPS has been rezeroed. DTC U1241 does not indicate a system malfunction and will not cause any warning indicators to illuminate. When DTC U1241 sets, cycle the ignition and use the scan tool to clear the code, no further diagnosis is necessary. For more detailed information concerning the PPS, refer toSIR System Description and Operation . For more detailed information concerning PPS flash code and rezeroing procedures, refer toPassenger Presence System Flash Code Procedures and Passenger Presence System Rezeroing Procedure .