9-5 Linear (9600) L4-2.3L Turbo (2.3t) (2004)
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Brake Fluid Pump: Description and Operation
ABS With TCS Only
Return Pump, ABS Function
Return pump, ABS function
The return pump is utilized in different ways, depending on whether the TC/ABS control module is working in ABS mode or TCS mode. The function
of the pump when the control module is in ABS mode will be described here together with an overall explanation of how the return pump works.
The return pump, which is integrated into the hydraulic unit, consists of a d.c. motor that actuates a hydraulic pump.
The pump unit, which is only activated when an outlet valve is open, returns surplus brake fluid to the master cylinder.
The pressure in the returned brake fluid is determined by the brake pressure in the master cylinder, which is in turn proportional to the pedal pressure
applied.
The pump's capacity of about 250 bar is sufficient for all braking conditions that occur.
The control module checks the operation of the pump once each time the ignition is turned on and the speed exceeds 6 km/h (3.7 mph), whereby the
pump operates for 200 ms. If the brake light switch is activated, this test will be conducted at 15 km/h (9.3 mph).
The hydraulic pump and electric motor are an integral part of the valve block and cannot be replaced separately.
Diagnostics
If a fault occurs in the pump motor or wiring harness, diagnostic trouble code C2465 will be set at the same time as the warning lamps for ABS, brakes
and TCS OFF light up as well as the central warning lamp.
Return Pump, TCS Function
Return pump, TCS function
The return pump is utilized in different ways, depending on whether the TC/ABS control module is working in ABS mode or TCS mode. The function
of the pump when the control module is in TCS mode will be described here.
The return pump is continuously active during TCS modulation with braking.
Pressure is built up by closing the pressure relief valve and opening the pressure increase valve to supply the return pump with brake fluid. The control
module closes the pressure increase valve when a preset pressure is reached.
