Tests AC: DTC B272D - Passenger Differential Temperature Fault

PINPOINT TEST AC: DTC B272D - PASSENGER DIFFERENTIAL TEMPERATURE FAULT

AC1:

AC2-AC5:

AC5-AC7:

AC8-AC10:

AC10-AC12:

AC12-AC14:

AC14-AC16:

AC16-AC18:

AC18-AC20:

AC20-AC22:

AC22-AC25:

AC25-AC27:

AC27-AC29:

AC29-AC31:

AC31-AC33:

AC33 Continued:

Normal Operation
Both the driver and front passenger climate controlled seats are independently controlled electronically by the dual climate controlled seat module (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 switch key ON engine OFF (KOEO). The system receives power from battery junction box (BJB) fuse 12 (30A) feeding battery voltage on circuit SBB12 (GN/RD) into DCSM C3305a pin F. The system also receives power from BJB fuse 11 (30A) feeding battery voltage on circuit SBB11 (BU/RD) into DCSM C3305a pin E. If power is disconnected from either pin E or F of DCSM C3305a with the power connection remaining on the other circuit, both seats will remain operational because the power 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 thermo-electric device (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 EATC seat switch 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 airflow restriction or a circuit fault of either TED area. 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.

Possible Causes
A driver differential temperature fault can be caused by:
- 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.
- a faulted cushion or backrest TED assembly.
- a faulted DCSM.