Reading Out Fault Memory / Eliminating Faults

Reading Out Fault Memory / Eliminating Faults

- Faults which were not present during the last journey and the test conditions applying them can not be measured (with one exception). The relevant fault path should therefore be inspected visually, since with this type of fault the cause is either poor electrical contact, contact resistance or corrosion at the plug connections.

Exception: "HF sensor signal not plausible" (fault code 1-4). This fault is always output by the system tester as "NOT PRESENT". However, it is possible that the fault is present and can be measured by way of the sensor test (menu 2).

- A displayed fault, for example "HF sensor ground short", refers not only to the HF sensor but to the complete circuit path as far as the control unit input.

- After eliminating the fault, erase the fault memory. After a short test drive (approx. 500 meters), read out the fault memory again.

- The fault code for the fault output is displayed as additional information if button 1 is pressed. In addition, from control unit software status R 02 on (introduced during 1991 model year), the road speed when the fault first occurred is memorized.

- If the 9288 system tester is connected, make quite sure that no speed range is selected at the automatic transmission, since when the engine is running the tester could increase its running speed.

- Not all system faults are identified by the RDK control unit as faults. This applies to the RDK control unit itself. If the fault display "RDK SHUT DOWN" appears and no fault is stored in the control unit, the following points must be checked or confirmed before the RDK control unit is replaced:

a. Is the control unit plug attached correctly and are the connection contacts between the plug and the control unit in good condition?

b. When the ignition is switched on, a voltage higher than 9 Volt must be present at PIN 13 (ground) and PIN 33 of the disconnected control unit plug.

c. There must be no break in the data line from RDK control unit PIN 2 to instrument cluster plug 2, PIN 11.

- The following display may appear as a fault output although no fault is present: Data line - interruption - not present (fault code 18).