Pinpoint Test BA : DTC B272D: Notes

Refer to Climate Controlled Seats , for schematic and connector information.

Normal Operation 

The Dual Climate Controlled Seat Module (DCSM) is supplied voltage at all times, but the climate controlled seat system only operates with the engine running. The system can be operated with the ignition ON engine OFF by using a scan tool to bypass the climate controlled seat buttons on the touchscreen interface. When commanding a heat or cool mode operation in this manner, the climate controlled seat system only operates in 15 second intervals. Both voltage supply circuits are spliced together internal to the DCSM, so if one circuit becomes open, both seats can still be operated. However, if a fault occurs setting a DTC specific to either climate controlled seat, only the affected seat is disabled by the DCSM.

The seat cushion is equipped with a Thermo-Electric Device (TED) assembly that includes a seat blower (fan motor, serviced as an assembly with the TED). Similarly, the 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 dependent on the commanded climate controlled seat settings.

A differential fault occurs when the cushion and backrest TEDs on an affected seat are reporting very different temperatures to the DCSM. This may result from an air flow restriction or a circuit fault of either TED area. If a TED and manifold is clear of obstruction and is operational, check the other TED and circuitry on the seat. It is important to note that a TED with a higher temperature may be operating correctly and is not the area of concern. The other TED may be indicating a much lower temperature, causing the DTC to set.

• DTC B272D (Passenger Differential Temperature Fault) - If there is a temperature differential between the passenger 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 sets. When this happens the first time in a key cycle, the DCSM puts the passenger seat system into recovery mode (see Principles of Operation). If the system is able to recover, it functions normally. If the system is able to recover and it occurs a second time in the same key cycle, the DCSM shuts down the passenger 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