Unable to Deactivate Brake Boost System in GDS 2

After the Brake Master Cylinder Assembly has been replaced on 2019-2020 XT4 models, a GDS 2 error message may display when trying to deactivate the brake boost system when performing the hydraulic bleed procedure.

Being unable to deactivate the brake boost system may be caused by the B20 Brake Fluid Level Switch and the B34D Engine Coolant Temperature Sensor 4 Connector being swapped during reassembly. If these connectors are swapped, DTCs C0049 SYM05 (Low Brake Fluid Indicated) will be stored in the Electronic Brake Control Module (EBCM) and a P2AFF SYM (Engine Coolant Temperature Sensor 4 Circuit High Voltage) will be stored in the Engine Control Module (ECM).

The Brake Fluid Level Switch Connector and the Engine Coolant Temperature Sensor 4 Connector are identical and can be easily swapped. The harness retainers and the wire colors are different.

Shown are the correct connections of the Engine Coolant Temperature Sensor 4 (Fig. 10) and Brake Fluid Level Sensor. (Fig. 11)

 

Fig. 10

 

Fig. 11

 

If the GDS 2 error message is displayed (Fig. 12), verify that the connectors are in the correct location.

 

Fig. 12

 

– Thanks to Christopher Hightower

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