Electronic Speedometer Test: 300SD
- Remove speed sensor from transmission tail housing. Turn ignition on. Place a large screwdriver blade across sensor tip. Move screwdriver blade off of and onto sensor quickly. Speedometer needle should move slightly. If needle does not move, remove instrument cluster and unplug 8-pin connector at back of cluster.
- Connect negative voltmeter lead to pin No. 3 (Brown wire) and positive voltmeter lead to pin No. 5 (White wire). See Fig 1. See 8-PIN INSTRUMENT CLUSTER CONNECTOR table. Repeat step 1). If voltage is indicated, speedometer is defective. If voltage is not indicated, replace speed sensor and/or harness.
Courtesy of MERCEDES-BENZ OF NORTH AMERICA. 15-PIN INSTRUMENT CLUSTER CONNECTOR (300SD)
| Pin No. |
Designation |
Wire Color |
| 1 |
Coolant Temperature Gauge |
Green |
| 2 |
Fuel Gauge |
Blue/Black |
| 3 |
Fuel Reserve Warning |
Blue/Green |
| 4 |
Low Oil Level Indicator |
Brown/Black |
| 5 |
Bulb Failure Indicator |
Gray/Purple |
| 6 |
High Beam Indicator |
White |
| 7 |
Power For Charge Indicator From Fuse No.7 |
Pink/Black |
| 8 |
Ground For Bulb Failure Indicator, Connects To Terminal No. 8 Of 8-Pin Connector |
Gray/Blue |
| 9 |
From Alternator & Light Failure Monitoring Unit |
Blue |
| 10 |
Park Brake & Low Brake Fluid Indicator |
Brown/White |
| 11 |
Brake Pad Wear Indicator |
Brown/Red |
| 12 |
Light Bar Power, From Terminal No. 7 Of 8-Pin Connector |
Black/Red |
| 13 |
Low Coolant Level Indicator |
Brown/Yellow |
| 14 |
Washer Fluid Level Indicator |
Brown/Blue |
| 15 |
Oil Pressure Gauge |
Brown/Green |
8-PIN INSTRUMENT CLUSTER CONNECTOR (300SD)
| Pin No. |
Designation |
Wire Color |
| 1 |
Panel Illumination Indicator |
Gray/Purple |
| 2 |
Not Used |
- |
| 3 |
Main Ground |
Brown |
| 4 |
Right Turn Signal Indicator |
Black/Green |
| 5 |
Speedometer From Speed Sensor |
White |
| 6 |
Left Turn Signal Indicator |
Black/White |
| 7 |
Speedometer/Tachometer Power |
Black/Pink |
| 8 |
Instrument Lights/Warning Buzzer |
Gray/Blue |
15-PIN INSTRUMENT CLUSTER CONNECTOR (300E)
| Pin No. |
Designation |
Wire Color |
| 1 |
Ground (W1) |
Brown |
| 2 |
Coolant Temperature Sensor |
Green |
| 3 |
Fuel Gauge Transmitter |
Blue/Black |
| 4 |
Fuel Reserve Indicator Transmitter |
Blue/Green |
| 5 |
Low Engine Oil Level Indicator |
Brown/Black |
| 6 |
From Fuse No. 5 |
|
| 7 |
High Beam Indicator |
White |
| 8 |
From Fuse Block Terminal No. 15 (Unfused) |
Pink/Red |
| 9 |
Charge Indicator Terminal No. 61 (Battery) |
Blue |
| 10 |
Brake Lining Wear Indicator |
Brown/Red |
| 11 |
Low Brake Fluid Switch |
Brown/White |
| 12 |
Low Coolant Indicator |
Brown/Yellow |
| 13 |
Light Failure Monitoring Unit |
Gray/Purple |
| 13 |
Ashtray Light |
Gray/Purple |
| 14 |
Left Turn Signal Indicator |
Black/White |
| 15 |
Right Turn Signal Indicator |
Black/Green |
4-PIN INSTRUMENT CLUSTER CONNECTOR (300E)
| Pin No. |
Designation |
Wire Color |
| 1 |
Windshield Washer Tank Level |
Brown/Blue |
| 2 |
Terminal Block Circuit No. 58d |
Gray/Blue |
| 3 |
Not Used |
Brown/Yellow |
| 4 |
Oil Pressure Sensor |
Brown/Green |