Peugeot 405 Manual

Anti-lock braking system (ABS) - general information
Braking system / Anti-lock braking system (ABS) - general information


General
1 ABS is available as an option on certain models covered by this manual, and is fitted as standard equipment on some models. The purpose of the system is to prevent the wheel(s) locking during heavy braking. This is achieved by automatic release of the brake on the relevant wheel, followed by re-application of the brake. The system comprises an electronic control module, a hydraulic modulator block, the hydraulic solenoid valves and accumulators, the electricallydriven pump, and the roadwheel sensors.

2 The system operates on all four wheels, and vehicles may be fitted with rear disc or rear drum brakes.

3 The system prevents wheel lock-up by regulating the hydraulic pressure to the brakes.

4 Solenoids (which control the fluid pressure to the calipers) are controlled by the electronic control unit, which itself receives signals from the wheel sensors (fitted to all four wheels), which monitor the speed of rotation of each wheel. By comparing these speed signals from the wheels, the control unit can determine the speed at which the vehicle is travelling. It can then use this speed to determine when a wheel is decelerating at an abnormal rate, compared to the speed of the vehicle, and therefore predicts when a wheel is about to lock. During normal operation, the system functions in the same way as a non- ABS braking system.

5 The ABS system is fail-safe, and should a failure occur, a self-monitoring test facility is incorporated in the system which can be used in conjunction with dealer test equipment for fault diagnosis.

6 Three different types of ABS may be fitted, depending on model, as follows.

Bendix integral ABS
7 This system is fitted to certain models up to 1993 as standard equipment. The system is fitted instead of a conventional system, and the brake pedal acts directly on the hydraulic control unit, which replaces the master cylinder and vacuum servo in a conventional braking system.

8 The system operates at very high fluid pressure, typically 158 to 183 bar, generated by an electric pump fitted to the modulator assembly.

9 The system is fail-safe and will continue to operate even if one wheel sensor should fail.

In the event of total failure, the control unit will revert the system to normal braking.

Warning: Due to the complexity of the system, the very high fluid pressures involved, and the need for special bleeding Bendix additional ABS
10 The Bendix additional system is fitted as an option to certain models, and the ABS components are fitted in addition to the conventional braking system components.

11 The system uses the pressure provided by the conventional master cylinder and vacuum servo.

12 The system is fail-safe, and conventional braking is maintained through the servo and master cylinder in the event of an ABS failure.

13 The braking system can be safely bled, and the fluid can be renewed as described in Chapter 1, as the system operates using the conventional pressure supplied by the master cylinder and servo.

Bosch 2E additional ABS 14 The Bosch 2E additional system is fitted to certain later models from 1993, and is similar to the Bendix additional system described previously.

equipment and pressure gauges, any operation requiring removal or disconnection of any hydraulic component, pipe or fitting must only be carried out by a suitably-equipped Peugeot dealer. Failure to heed this warning may result in personal injury, or malfunction of the system at a critical time. Work on vehicles equipped with the Bendix integral ABS should therefore be confined to routine maintenance operations.


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