C220 1995 - Speedometer + Brake indicators failure

[lsl]

All of a sudden,
1) the speedometer stopped working
2) parking brake indicator stays lit
3) brake pads indicator stays lit
4) ABS indicator indicator stays lit

Any idea of what the cause may be?

 

[television]

You have lost a speed signal, I have not heard of this one on your car, but I will see what I can find tomorrow

 

[lsl]

Very much appreciated.

I was thinking that maybe one of many connectors to the instrument panel is loose or disconnected (I'm supposing here, I never looked at the panel or saw a schematic). Would you know if there is indeed a connector which carries speed data as well as ABS, parking brake, and pads sensors?

Thanks

 

[anyweb]

there are two connectors on the back of your instrument cluster,

it is very unlikely that one of them is loose as they are held in place with clips which are either open or closed, if open no signal will travel through them,

to examine the cluster, REMOVE the key from the ignition, and either using the mercedes tools for the job (i bought them from the dealer, 20quid) gently slide out the cluster maneovering it left and right until you can free it. remember do NOT turn on the ignition when the cluster is out as if you disconnect one or both of the connectors then an SRS fault will register (making it necessary to visit the dealer for a reset).

the part number of the mercedes tools is W 140 589 02 3300 and they are basically very strong wire's with a holder on one end and a small hook on the other (used for grabbing the cluster and pulling it out).

let us know how you get on

and did you check ALL your fuses ?

cheers
anyweb

 

[C220GJS]

Check the fuse on top of the OVP relay ,tall silver relay in the ECU compartment at the passenger side rear of the engine bay.
This may link to you other problem.

 

[BlackC55]

On your car I think there is a speed sensor on the diff.

I suspect this has gone open circuit.

 

[television]

Have you changed the radio recently

 

[lsl]

- I did check all the fuses, including the one in the ECU compartment. All fine.
- I did not change the radio
- I disconnected the battery for 10 minutes yesterday, no change.

- 2 days before the failure, I disassembled the shifter (from inside the car) to replace the bushing that connects to shifter to the transmission lever. While doing that, I suspect I might have pulled a cable (although I think I was very gentle).

One thing I did at the same time, is that I removed the ash tray and saw the cause of a rattle that bugged me for 11 years! There was a loose unused connection which I beleive is for the cell phone option. I wrapped in with some clothe and tie wrapped it to the cable bundle.

 

[television]

Then something has come out of something, you have lost or shorted out the speed signal.

Nothing else can do this.

the odd man out is the brake wear sensor as this is not part of any system and is a closed circuit in its self

 

[lsl]

Is it possible that the instrument panel itself failed? Is it common? The 3 lights (ABS, Pads, Parking) that come up actually lit when the key is at ON, and they shut off when the engine starts, then they lit again approx 1 sec after ignition.

I also noticed that when I start moving the car with the parking brake activated (for real), the beeper does not sound anymore. I therefore suspect that this is simply due to the instrument thinking that the car does not move.

Do you know if the speed sensor cable is routed below the radio, and then near the shifter assembly? Is the sensor in the differential?

 

[television]

Is it possible that the instrument panel itself failed? Is it common? The 3 lights (ABS, Pads, Parking) that come up actually lit when the key is at ON, and they shut off when the engine starts, then they lit again approx 1 sec after ignition.

I also noticed that when I start moving the car with the parking brake activated (for real), the beeper does not sound anymore. I therefore suspect that this is simply due to the instrument thinking that the car does not move.

Do you know if the speed sensor cable is routed below the radio, and then near the shifter assembly? Is the sensor in the differential?

It looks as though the instruments are reading correctly and you have just lost the speedo somehow or the fault is in the cluster, I will have a further look

 

[lsl]

News with this problem.

Everything started to work while driving. Worked for a day, then appeared again the next day. Really, the speedometer and the 3 indicators fail together. I also saw once the check engine blink for 1/3 of a second.

Start to suspect the instrument cluster. I took it out, and inspected the circuit board. Nothing obvious.

Anyone knows about a common connector where these 4 signals may go through?

 

[television]

As I have said before I think that it within the cluster, if the PCB has a break in a tract this could do it.

The problem for you is that the breaks cannot be seen with the eye, and can only be checked with an Ohm meter / continuity meter

 

[lsl]

Made some progress with this problem. I bought the C220 full schematics on e-bay and I discovered that the ABS, Brake Pad, and Parking Brake (for fluid failure) are all controlled from the ABS module. Moreover, the speedometer signal is also routed through the ABS module before going to the instrument panel.

That is, I strongly suspect the ABS module. The problem is that the schematics tell me that the ABS module is located next to the cruise control and ECU modules in the engine compartment. I did not find it!

Anyone knows where the ABS module is located on a 1996 C220?