2002 Sienna Vsc/abs/trac Off Lights On With Code C1249/c1246

[2002owner]

I have a 2002 Sienna, 83k. Recently, VSC/ABS/TRAC OFF lights on after normal driving for a while (local/highway). The code reads c1249 and c1246. Lights stay on till turn off the engine. Next time turning on the engin, everything is fine, but they will come back don't know when while driving (it looks like that the lights on randomly then stay ). My dealer said I need to change Brake Master Cyclinder, which can not fully release the pressure while releasing brake pedal after a daylong testing. They can't guarantee the issue is solved, but the part has to replace before further diagonsis.

Somehow, it can not convince me. I googled those two codes. They are related to brake system, but will Brake Master Cyclinder defect trigger the error code. The dealer told me c1246 might related to c1249, which points to "master cylinder presurer sensor". Is it the fault of sensor or the master cylinder ?

Any advice? Please. I am frustrated since no one can identify the problem and the safety concern. BTW, this happened after I change front brake pad. Are they related?

Thanks in advanced.