I have a 1991 300E 4matic which has a few faults which may be related, the main one is the 4matic is not operative.

I have noticed that the 4matic light doesn't light up on ignition start up. I also have a low speed ABS fault, and the rear diff locks up at low speed in tight bends, although this only happens after the car has been running for 20 mins or so.

It is possible the faults are linked, eg faulty abs sensor, but this wouldn't explain the 4matic light not lighting up when the ignition is turned on. Through reading the various threads my thoughts are:-

1. Dead 4matic ECU
2. Blown 4matic bulb (does this stop 4matic working?)
3. Faulty OVP - fuses are ok in it.
4. Faulty ABS Sensor

Does the 4matic have a seperate fuse?

Any help would be greatly appreciated.

I had trouble with my 92 300TE4 4matic unit recnetly and had to replace it.

I believe if you have trouble with the 4 matic unit the light always come on
so I would check:

Is bulb burned out?

Did someone put your car in test mode so it will only run in 2 wd?
If it's in test mode and the battery terminal has been disconnected
then reconnected the light stays off

Jim

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92 300 TE 4matic

Hi Jim,

The car wasn't in test mode when i discovered the light wasn't working, although I have disconnected the battery since to see if the ecu would reset.

I have read that if the bulb has gone, this also disables the 4matic, but not sure if this is correct.

My OVP seems fine, but was wondering if my slow speed break pedal stutter which is an ABS fault could be being caused by a duff OVP, which in turn is not giving any power to the 4matic ecu?

Justin

I have the same car.

What 4matic light are you referring to, the triangle or the lower dash light?

On mine, the triangle lights up upon start up, but not the other one (I am assuming that I need to replace that bulb.) Also, my 4matic works some of the time, but all of the time. The rear wheels have been known to spin.

I doubt that the 4matic is dependent upon the bulb, but that would be an easy fix if that was the case.

Hi

The lower dashboard light, not the triangle one higher up, that lights up fine. Reading the manual the 4matic light should come on with the ignition and then turnoff after the engine has started.

I read on another forum that a tech disabled the 4matic by removing the bulb?

What I am trying to work out is what other factors could cause the 4matic symbol not to light up other than a blown bulb, eg OVP, or 4matic ECU.

Justin