Apparatus in braking system, for diagnosing pressurizing device based on fluid pressure detected during operation of the device prior to operation of the braking system

A diagnosing apparatus for diagnosing a first pressuring device and a second pressurizing device provided in a hydraulically operated braking system which includes (1) a master cylinder having two pressurizing chambers and operable by a brake operating member to generate in said two pressurizing chambers a hydraulic pressure corresponding to an operating force acting on said brake operating member, (2) a first group of brake cylinders connected to a first fluid passage extending from one of said two pressurizing chambers, and a second group of brake cylinders connected to a second fluid passage extending from the other of said two pressurizing chambers, and (3) said first and second pressurizing devices operable to deliver a pressurized fluid through said first and second fluid passages, respectively, while said brake operating member is not in operation, characterized by comprising:

• a first and a second pressure detecting device connected to said first and second fluid passages, respectively;
• and
• a diagnosing device operable to determine whether at least one of said first and second pressurizing devices is abnormal or not, on the basis of a difference between hydraulic pressure values detected by said first and second hydraulic pressure detecting devices while said brake operating member is not in operation and while said first and second pressurizing devices are operated in the same operating condition.