Pinpoint Test AS: DTC B272B: Notes

Refer to Climate Controlled Seats for schematic and connector information.

Normal Operation 

Both the driver and front passenger climate controlled seats are independently controlled electronically by the DCSM mounted to the bottom of the passenger seat cushion. The climate controlled seat system only operates with the engine running, however, if using a scan tool to command the DCSM, diagnostic testing can be carried out with the ignition ON engine OFF. The system receives voltage from BJB fuse 67 (40A) feeding battery voltage on circuit SBB67 (BU/RD) into DCSM C3265A pins E and F. If voltage is disconnected from either pin E or F of DCSM C3265A with the voltage connection remaining on the other circuit, both seats will remain operational because the voltage feed circuits are connected internally in the DCSM. However, if a fault occurs setting a DTC specific to either climate controlled seat, only the affected seat will be disabled by the module and the other will remain operational.

Each driver and front passenger seat cushion is equipped with a TED assembly that includes a seat blower (fan motor, serviced as an assembly with the TED). Similarly, each driver and front passenger seat backrest is also equipped with its own TED assembly with blower. Cabin air is drawn through the blower and distributed to each of the TED modules located in the seat cushion and backrest. The TEDs then heat or cool the air. The air is then directed into the foam pad and manifold where it is distributed along the surface of the cushion and backrest of the seat. Once the system is activated, the DCSM uses a set of flexible algorithms to control the heating/cooling modes and the blower speed, dependant on the climate controlled seat switch settings.

• DTC B272B (Passenger Back-Over Temp Detected) - In the heating mode, if the passenger seat backrest TED temperature exceeds 85 °C (185 °F) for more than 4 seconds, the TED is disconnected or the duct is blocked, the DCSM shuts down the passenger seat system and set this DTC. Incorrect use of the climate controlled seat by repeated switching between heat and cool modes or excessive passenger compartment temperature also sets this DTC.
• DTC B272B (Passenger Back-Over Temp Detected) - In the cooling mode, if the passenger seat backrest TED temperature exceeds 70 °C (158 °F) for more than 4 seconds, the TED is disconnected or the duct is blocked, the DCSM shuts down the passenger seat system and set this DTC. Incorrect use of the climate controlled seat by repeated switching between heat and cool modes or excessive passenger compartment temperature also sets this DTC.

This pinpoint test is intended to diagnose the following: 

• Wiring, terminals or connectors
• Restricted passenger seat backrest TED filter
• Crushed or restricted passenger seat backrest foam pad
• Crushed or restricted passenger seat backrest climate controlled seat manifold
• Passenger seat backrest TED assembly
• DCSM