Test 6: Speedometer

Disconnect the ABS control module harness connector. See Figure . Connect Signal Generator (DTR-8416) between ground and terminal No. 5 (terminal No. 18 if equipped with ASR) at ABS control module harness connector, according to manufacturer's instructions. See Fig 1 or Fig 2 . Set voltage amplitude on signal generator to 10 volts.
Turn ignition switch to RUN position. When frequency is increased on signal generator, speedometer reading should increase. If speedometer responds as specified, check signal output from ABS control module. If speedometer does not respond as specified, check wiring and electronic circuit board. If wiring and circuit board are okay, replace speedometer.

Fig 1: Identifying ABS Control Module Harness Connector Terminal No. 18 (With ASR)

Courtesy of MERCEDES-BENZ OF NORTH AMERICA

Fig 2: Identifying ABS Control Module Harness Connector Terminal No. 5 (Without ASR)

Courtesy of MERCEDES-BENZ OF NORTH AMERICA