Test Point 21
Fault Code 21W-line (DME immobilizer) Interruption.
1. Pull off Plug I on the alarm control unit.
2. Pull off the DME plug.
3. Ohmmeter at Plug I, alarm control unit pin 23, and DME plug pin 88.
Display: < 5 Ohms
NOTE: The line runs via plug connection X 3/1 pin 14.
4. Ohmmeter at Plug I alarm control unit pin 23 and ground.
Display: infinity Ohms
5. Voltmeter at Plug I alarm control unit pin 23 and ground.
Switch on the ignition.
Display: 0 volt
If no fault can be detected, try replacing the alarm control unit. If the fault is still present, the DME control unit is faulty.