| ABS BOSCH 5.7 and BOSCH 8.0 |
| As the control units are interlinked over two data BUS lines, always start fault finding by interrogating the contents of the fault memories of all the control units fitted to the vehicle. |
| The interrogation of the fault memory can be performed with the vehicle system tester -V.A.G 1552- by the „automatic test sequence“ (activation with the key function 00) → Chapter or with the vehicle diagnosis system, measurement and information system -VAS 5051- → Chapter |
| When doing so check whether a possibly stored fault might affect the ABS system. |
| The ABS control unit -J104- together with the hydraulic unit for ABS -N55- forms a compact unit. This unit is located in the right of the engine compartment. The control unit is equipped with a fault memory. The diagnostic connection for self-diagnosis is located in the storage compartment on the driver's side. |
| Self-diagnosis relates to the electrical/electronic part of the ABS, i. e. faults are detected only over the electrical connection to the control unit (e.g. open circuit to a wheel speed sensor). |
| The control unit detects faults while the vehicle is being operated and stores them in a permanent memory, |
| whose information is retained even if the battery voltage is disconnected. Faults which occur sporadically (isolated) are likewise detected and stored. If this fault no longer occurs during 40 vehicle starts and driving-off procedures, it is erased from the fault memory (fault delete counter), with the exception of the fault „Control unit defective“. |
| After the ignition is switched on the ABS warning light -K47-, the red dual circuit and hand brake system warning light -K7- and the traction control system warning light -K86- or the ESP and TCS warning light -K155- light up for approx. 2 seconds. |
| During this period a test sequence (self-check) is performed in the control unit with the following functions: |
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| Test of supply voltage, min. 11.0 Volts |
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| Test of control unit including valve coils. |
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| Electrical test of wheel speed sensors; not fully completed until vehicle reaches 20 km/h. |
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| Check of control unit coding |
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| Test of electric motor for return flow pump. |
| Systematically initiate self-diagnosis before the start of fault finding and retrieve the stored information using vehicle system tester -V.A.G 1552- → Chapter or using vehicle diagnosis, measurement and information system -VAS 5051- → Chapter. |
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| The description → Chapter relates to the vehicle system tester -V.A.G 1552- using the current program card. |
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| The use of fault reader -V.A.G 1551- with integrated printer is similar. A minor deviation on the display read-out is possible. |
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