Safety Precautions And Troubleshooting, BOSCH 5, From My 96

Troubleshooting

• The ABS, ABS/EDL and ABS/EDL/ASR are vehicle safety systems. Knowledge of the systems is required before starting any work.
• Always check the Diagnostic Trouble Code (DTC) memory before starting work on the ABS, ABS/EDL or ABS/EDL/ASR system.
• Do not drive the car with the ABS, ABS/EDL, or ABS/EDL/ASR control module harness connector disconnected.
• Do not connect or disconnect ABS, ABS/EDL or ABS/EDL/ASR components unless the ignition is switched off.
• Bolts on the hydraulic unit must not be loosened. An exception to this is the bolt for the cover, when replacing the relays for the return flow pump and the solenoid valves.
• Pay attention to the applicable safety precautions when handling brake fluid HYDRAULIC SYSTEM, BLEEDING .
• Malfunctions in the ABS, ABS/EDL or ABS/EDL/ASR system are indicated by the warning lamps. As certain malfunctions cannot be detected unless the vehicle is moving it is then necessary to check the system by conducting a road test with the vehicle driven at a speed of at least 60 km/h (38 mph) for a period of 30 seconds.

Test Prerequisites

• Approved wheels and tires of identical size, and all the tires inflated to the correct pressure
• Conventional brake system together with brake light switch and brake lights in proper working order
• No leaks at any hydraulic connections and lines (visual inspection of hydraulic unit, brake cylinders, etc.)
• Wheel bearings and bearing play in order
• Installation positions of ABS wheel speed sensors in order COMPONENT LOCATION OVERVIEW
• All fuses OK
• Ground (GND) connection for ABS return flow pump -V39- at hydraulic unit OK
• Harness connector for ABS Control Module (w/EDL) -J104- correctly installed; catch/lock properly engaged
• Battery Positive Voltage (B+) OK (at least 10.5 V)

The On Board Diagnostic (On Board Diagnostic) program can be started only if the vehicle is stationary and the ignition is switched on (or the engine is running). It is not possible to start the On Board Diagnostic program if the vehicle is moving at a speed greater than 2.75 km/h (approx. 2 mph); in other words, none of the four wheels should be moving.

It is important to make sure that vehicle electrical components are not exposed to any electromagnetic interference when testing the ABS, ABS/EDL or ABS/EDL/ASR system; in other words, keep equipment with a high power consumption, e.g. electric welding equipment, away from the vehicle.

Required Technical Information

• Valid wiring diagram
• Electrical component locations
• Brake mechanical components OVERVIEW - FRONT BRAKES
• Brake hydraulic components, brake servo unit OVERVIEW - BRAKE BOOSTER/BRAKE MASTER CYLINDER