14:19. Components of system of anti-blocking of brakes (ABS) - the general information

The ABS system is run by the electronic actuation device (ECU) which has ability to diagnose a condition of all components of system, including itself. At detection by the electronic actuation device of malfunction, it gives a signal on shutdown of the ABS system and on inclusion of an alarm lamp of the ABS system installed on an instrument guard. At the same time brake systems begins to function as usual, without the ABS system. If the malfunction nature such is that it interferes with operation of the ordinary brake system, the electronic actuation device makes also inclusion of an alarm lamp of a usual brake.

In case the alarm lamp of the ABS system is included, indicating malfunctions in system, to make diagnostics of malfunction without connection to the electronic actuation device of the external diagnostic equipment very difficult. Therefore, this section first of all contains the list of the main checks which can be made for the purpose of check of integrity of system (for example whether the amount of brake fluid is enough, whether there are no leaks, etc.). Information provided in the Section Removal and installation to the place of ABS system components is limited to the description of removal and installation to the place of sensors of wheels of the ABS system and the block of the electronic actuation device as in some circumstances performing removal of these components is necessary for ensuring access to other systems of the car.

If malfunction cannot be immediately identified by means of the list of checks given below, the only way of further actions is the car otgonka on survey in representative office of SAAB. The diagnostic equipment defining a cause of defect has to be connected to the electronic actuation device of the ABS system. For safety reasons owners of cars strictly are not recommended to try to make diagnostics of malfunction of the ABS system by means of the standard electric equipment.

Checks on search of the main malfunctions

Level of brake fluid

Park the car on a plain surface and make check of level of brake fluid at completely filled accumulator of the hydraulic booster. To make sure that the accumulator is completely filled, include ignition and listen to operation of the hydraulic pump which is an element of the hydraulic block in assembly. The sound made during the operation of the pump will be well heard; after a pump stop the accumulator is completely filled. Switch off ignition and without touching a brake pedal, check liquid level in the tank. If necessary add in the tank liquid of the required grade before reduction of level to a mark a maximum.

If liquid level too low, then is available suspicion on existence of leaks somewhere in hydraulic system. Make check of all brake hoses and tubes (address the Head Routine maintenance). In case leaks are not found, remove in turn each wheel and check whether there are no leaks via pistons of brake supports - address the Sections Removal, capital repairs and installation to the place of a forward brake support and Removal, capital repairs and installation to the place of a back brake support.

Relay and safety locks

Safety locks and relay of the ABS system

1 — the Relay of the motor of the hydraulic pump
2 — the ECU Relay
3 — the Safety lock of ECU 10 A

4 — the Safety lock of ECU 30 A
5 — the Safety lock of the motor of the hydraulic pump 30 A


Safety locks (and the relay) the ABS systems are located in a separate protective box in a motive compartment in the neighbourhood with the tank of brake fluid. Uncover also one behind one take each safety lock. Visually examine thread of each safety lock if it is visually difficult to define whether the safety lock is fused or not, make check of electric conductivity of a safety lock by means of a tester or the indicator of conductivity. If any of safety locks are fused, do not establish on their place new until the reason of burn-out of safety locks is not found and eliminated; provide the car for survey in representative office of SAAB and inform the expert on your finds.

Safety locks are intended for protection of the equipment and people against damages; the fused safety lock indicates existence in system of malfunction. Simple replacement of a safety lock or even installation of a crossing point on old before the problem is not fixed, increases risk of malfunction and can be a cause of the fire.


The relay of system is in the same protective box, as safety locks. To usually make check of the relay without special knowledge in the field of electronics quite difficult. However, switching of metal contacts in the relay can usually be heard. If the suspicious relay does not behave thus at inclusion of ignition, then it can be faulty. It is necessary to notice that such check is not convincing; the only way to be convinced of serviceability or malfunction of the relay is its replacement on obviously serviceable. If there are suspicions on malfunction of any relays, they can be replaced by their extraction from nests - remember at the same time their arrangement - and replacements on new.

Electric contacts and points of grounding

The environment in a motive compartment is aggressive in relation to electric contacts and breakdown even of the best isolation is sometimes possible. Water, chemicals and air cause bystry corrosion of electric contacts which is the reason of bad conductivity, and sometimes changeable conductivity. Disconnect a negative wire of the battery, then check reliability of fastening and a condition of all electric contacts of the hydraulic block of the ABS system which is on a back partition of a motive compartment. Disconnect each electric socket and examine contacts in it.

At detection on contacts of dirt make cleaning of contacts with the help of the special cleaning oil which is available on sale in most shops of automobile accessories and repair shops. Avoid cleaning of contacts by an edge as scraping of a surface of contact can lead to its further corrosion. Cleaning of contact with the help pure неворсящейся will provide to the rags moistened in the cleaning oil achievement of the pure brilliant surface of contact guaranteeing good electric conductivity.

Also check reliability of fastening and a condition of the plug of grounding on a forward part of the hydraulic block.