This manual describes testing procedures and serves as a troubleshooting guide for the ABS systems installed in Porsche 928 and 944 series vehicles.
The troubleshooting program consists of two test plans.
Test Plan No. 2 is required for testing procedures using the Bosch ABS-2-LED Testing Unit.
Both testing units can be used for all Porsche vehicles fitted with ABS.
The testing program is valid for all 8-cylinder vehicles from '84 models onwards and all 4-cylinder vehicles from '87 models onwards.
Test data for 928 S - USA, Model Year '86
The test data and electrical circuit diagram for 928 S Model Year J86 apply to chassis numbers from VIN 927 GS 86 1001 onwards.
U.S. specification 928 S vehicles of Model Year '86, with chassis numbers from VIN 929 GS 80061 to 922 GS 860936 are equipped with the Model Year '85 form of ABS system.
The test data and electrical circuit diagram for Model Year '85 apply to the above vehicles.
The (Bosch) three-channel ABS system ¡s provided with one speed sensor per wheel. The braking system is divided front and rear (black/white division), i.e. one brake circuit operates on the front axle (push rod circuit) and the second on the rear axle (floating circuit).
1 — Tandem brake master cylinder
2 — Hydraulic unit
4 - ABS control unit
5 — ABS indicator lamp
6 - Stop lights
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