Pinpoint Test AT: DTC B272C: 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.

A differential fault occurs when the cushion and backrest TEDs on the seat are reporting temperatures to the DCSM with a difference between them of 60 °C (108 °F) or greater. This can result from an airflow restriction or a circuit fault at either TED. If a TED and manifold is clear of obstruction and is operational, the other TED and circuitry on the seat should be checked. It is important to note that a TED with a higher temperature may be operating correctly and not the area of concern. The other TED may be indicating a much lower temperature, causing the DTC to set.

• DTC B272C (Driver Differential Temperature Fault) - If there is a temperature differential between the driver backrest and cushion TED of 60 °C (108 °F) or more for more than 4 seconds, the TED is disconnected or the duct is blocked, this DTC will set. When this happens the first time in a key cycle, the DCSM puts the driver seat system into recovery mode, refer to Principles of Operation. If the system is able to recover, it will function normally. If the system is able to recover and it occurs a second time in the same key cycle, the DCSM will shut down the driver seat system.

This pinpoint test is intended to diagnose the following: 

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