Removing Note

In left-hand drive vehicles the electronic control unit is located on the driver's side, above the hood release on the side panel of the footwell In right hand drive vehicles the electronic control unit is located above the central fuse relay board. 1. Move back seat and pull up steering wheel (to make job easier). 2. Press spring-loaded lock and pul plug off of electronic control unit. 3. Take electronic control unit off of bracket after unscrewing mounting nuts. 1. Mount electronic control...

Test Cycle

Porsche 928 Ceb

An integrated test program runs off in the control unit when switching on ignition. A further test program runs off at a road speed of 6 krn h. Testing at 6 km h can be felt, since pump in hydraulic unit will run briefly. Test cycle is repeated each time car moves off, if ignition had been turned off previously. Testing includes electronic control unit, hydraulic unit, speed sensors, relays and wire harness. A shortcoming is shown by the ABS indicator lamp coming on. If the shortcoming is...

Connecting Tester

Turn off ignition and pull off multiple pin plug (35-pin) (2) on electronic control unit (1 > Control unit remains installed. 2. Connect multiple pin plug (2) of electronic control unit with plug (3) of tester. 3 Connect plug (4) ol tester on electronic control unit (1) so that spring-loaded lock is heard to engage on plug, 4. Turn on ignition all other electric equipment must be switched off.

Brake Pressure Regulator

A brake pressure regulator is installed in rear wheel brake circuit at outlet of hydraulic unit. Brake pressure regulator has a fixed switching-over pressure. There is an equal amount of pressure on inlet and outlet sides of brake pressure regulator until the switching-over pressure has been reached. As pressure increases on tho inlet side the outlet pressure will be reduced according to setting of brake pressure regulator. a ABS-relay C - relay XVII on CEB b Solenoid relay d on hydraulic unit...

Relay Operation

A ABS-relay C has overvoltage protection in form of a Zener diode. When reaching an overvoltage of 22 V e. g. defective alternator , this diode will be conductive and prevents further increasing in voltage. This protects control unit against damage from excessive voltage. b Solenoid relay d closes when ABS control unit receives voltage from alternator. This causes ground connection of relay term. 85 via the control unit. Relay switches over and supplies battery 30 to solenoid valve coils. If...

Pressure Holding Phase

If the braked wheel reaches the lock limit by way of hydraulic pressure from the brake master cylinder, further pressure increase in the wheel brake cylinder will be prevented. The solenoid will receive current of approx. 2 amperes, valve piston is activated and outlet as well as inlet of solenoid valve are closed. Hydraulic pressure between hydraulic unit and wheel brake cylinder remains constant. brake c Electric solenoid valve, front, right d Electric solenoid valve, front, left e Electric...

Test Program

Electronic Brake Force Wire Hardness

General Information 1 ABS in Operation 2 ABS in Porsche 928 3 Main Features 5 Hydraulic Unit 7 Speed Electronic Control Wire Harness, Relays, Overvoltage Stop Light Switch Brake Master Cylinder Brake Pressure Regulator Wiring General Hydraulic Unit Removing and Electronic Control Unit Removing and Installing v . . 33 Speed Sensors Removing and Testers and Tools Tester Test Steps 1-24 PORSCHE 928 S with Antiblock System ABS The antiblock system is an important contribution to improvement of...