With the new wiring (wiring diagram 625 540 36 00/625 540 37 00), see Workshop Manual, Electric system, Volume 4) at this input only the connection to the ABS control module is connected via the B-module (II 14/12). A dynamic function check of the ABS control module cannot be carried out. If the retarder does not function with this wiring (no fault code), actual value 10 and 11 (for switching off the retarder) must be checked. If ON is displayed with actual value 10 when the vehicle is stationary:
1. Check cable from the TCC control module to the B-module and to the ABS control module for short-circuit to ground.
2. ABS control module defective.
3. TCC control module defective.
4. B-module defective.
With the previous wiring (wiring diagrams W54-2328-71, W54-2329-71, W54-2341-71 and W54-2349-71: see Workshop Manual, Electric system, Volume 4), the clutch switch, closed throttle switch and neutral position switch are connected to this input via the relay K4-A35.
If ON is displayed when the vehicle is stationary and without any operation (a), b), c)) (see 1. to 4.):
5. Relay K4-A35 defective or short-circuit to ground in supply lead.
6. Pressure switch on clutch booster (servo unit) defective.
7. Check closed throttle switch (actual value 08 with EMR, actual value 14 with FMR).
8. Check neutral position switch (visually inspect green indicator lamp in M-module).
9. Cable short-circuit to UB+ in wiring to clutch pressure switch, closed throttle switch, neutral position switch or diode V1 to V3-A63.
If ON is not displayed for a function (a), b), c)), check the respective circuit (another circuit diagram may apply).