DPB_a025_backupCircuitLeakage

Power braking assist reduced

What does the DPB_a025_backupCircuitLeakage alert mean?

A leak or air in the backup hydraulic circuit is detected.

What triggers it

A leakage of brake fluid in the brake system: 1) Brake lines of wheel circuits FL, FR, RL, RR, 2) Output valves of wheel circuits FL, FR, RL, RR, 3) Low pressure seal of main brake cylinder 1 piston, 4) PSV valves of plunger. 5) Significant air in the brake system. An air in the brake system: - wheel circuits (incl. callippers) FL, FR, RL, RR, - main brake cylinder primary circuit (1), - main brake cylinder secondary circuit (2), - internal circuit below CSV, LEM evaluates pressure behaviour based on the active test sequence. The test sequence is executed in Postrun phase after a usual driving situation. Hereby the plunger provides a hydraulic pressure and stops. If pressure is dropping, then a leakage can be calculated. AIM evaluates pressure behaviour based on the active test sequence. If a combination of leakage and air is too high then the fault is set.

When it clears

1.Before fixing the fault, Check the fluid level in the brake fluid reservoir and fill it up if necessary. 2.Turn ignition on. 3.Drive the vehicle with vVehicel > 30 kph for longer than 30 s. 4.Stop and park the vehicle. 5.Turn ignition off. 6.Wait until Ecu sleep (min 200 s). Note 1: Do not use\apply any devices, which may interrupt the postrun procedure of the vehicle (e.g. opening the doors, activation of air conditioner, power seat, car radio etc.). Note 2: The transmission can be applied for parking as usual: AT - P-position, MT - e.g. 1- or R-gear. Note 3: The parking brake can be applied for parking as usual.

Potential impact

Hyrdraulic pressure may drop during a leakage test. System will be running with internal degraded pedal map. Braking may require increased effort.

Affected models