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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.