Mercedes Repair Questions? Ask a Mechanic for Answers ASAP
Acceleration Slip Regulation (ASR) light is on with fault code 13.
1. Test fuse #5 in front fuse panel.
2. Locate stop lamp switch. Test for key on battery voltage at Red/Blue wire with brake pedal not pressed. Press brake pedal and voltage should drop to less than one volt.
3. Test voltage at Black/Red wire, key on battery voltage with pedal pressed. With pedal not pressed, voltage should drop to less than one volt.
FuseStop Lamp SwitchStop Lamp Switch Wiring
THe ASD lights stands for the Automatic locking differential.
Description and Operation
The automatic locking differential (ASD) engages the differential lock only when needed, and is electronically controlled. A function indicator lamp, located in the speedometer shows engagement.Signals from the speed sensors are relayed to the ASD control unit which processes an average speed of the front and rear wheels. The control unit uses this information to send a signal to the solenoid valve in the hydraulic unit. The hydraulic oil is stored under pressure and then within fractions of a second is sent from the pressure reservoir to the differential housing at the rear axle. The hydraulic clamping force of the multi-disc clutch locks together the differential rotation between the rear wheels. This lockup transfers the road torque lost by the slipping wheel to the wheel with traction.
The light is on because you have a code in the computer.
Reading Diagnostic codes in the computer using the Warning Lamp
Start engine. Using suitable jumper wire, connect diagnostic test connector terminals 1 and 5 for about 1 second. Remove wire, warning lamp goes out for about 2 seconds, then flashes at 1 second intervals. The number of blinks indicates the malfunction code. Malfunction codes are as follows:Code 1: No malfunction. Code 2: ASD control unit faulty. Code 3: Stop lamp switch, ASD engagement function faulty. Code 4: No left front wheel speed sensor. Code 5: No right front wheel speed sensor. Code 6: No rear axle speed sensor. Code 7: No wheel speed signal from any sensor. Code 8: ASD value or stop lamp switch engagement faulty.
The ASR light stands for Acceleration Slip Regulation and the ABS light obviously is for the Anti lock brake system.
The reason for these lights coming on is because you have a code in the ABS system. You will need to get your ABS computer scanned for codes and fix the area of concern.
Unfortunately, you will need to go to a shop that has a scanner that can pull codes from your ABS system. There is no way to pull codes from the ABS system without the use of a scan tool.
THe diagnostic procedure and a list of the codes are listed below.
Displaying & Reading Trouble Codes (DTC Memory)
Traction Systems (ABS, ASR, ETS) and Speed-Sensitive Power Steering (SPS)
Models 129, 140 as of 06/94 up to 08/95 (ASR, ETS, SPS)
Preparation for DTC Readout
Connect impulse counter scan tool or Hand-Held Tester (HHT) to data link connector (X11/4) according to connection diagram.
Connect yellow wire from impulse counter scan tool to:ASR/SPS or ETS/SPS control module (N47-1 N47-2): socket 6EA/CC/ISC control module (N4/1): socket 7Base module (N16/1): socket 8Engine control module (N3/4): socket 4LH-SFI or right LH-SFI control module (N3/1, N3/3): socket 4Left LH-SFI control module (N3/2): socket 5DI or right DI control module (N1/3, N1/5): socket 17Left DI control module (N1/4): socket 18
Ignition: ON Read out DTC memory for control modules.