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1991 300E 4matic
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Discussion Starter #1
Hey guys,

My 1991 300e 4-matic system died a couple weeks ago. The amber 4-matic light on lower right side of instrument cluster is on. I am unable to pull codes with the impulse counter. All other pins in the x11/4 operate properly and am able to retreive codes on all except 4-matic pin 5. I checked the voltage at pin 5 of x11/4 and it is at 1.7 volts. When I unplug the 4-matic module the pin voltage is 12.5 volts. I have another 4-matic module and tried swapping them, but the condition is still there. Has anybody ran into anything like this in the past? :surrender:
 

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'92 300TE 4matic 280,000miles, '92 300TE 4Matic 'Ice Blue Metalic' 101,000miles
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10,399 Posts
You have to be logical and break the system down to its different functions. Is the fluid low in the reservoir and/or have you had a leak? What do you mean it "died"? Can you go in snow or a wet parking lot, force the car to skid and not see the main 4matic light come on....or feel the car do nothing during the skid? You're gonna have to give more info than this.....

You could have a failed pressure transducer in the 4matic valve or even a failed 4matic valve accumulator. Could even be the piston inside the TC. You can pull the fill plug in the TC and if you see hydraulic oil mixed with ATF weeping out, you're done...it's over unless you want to inject thousands or go with used TC's of dubious repair. You'd be incredibly lucky if it's just an electric/electronic snafu....but worth checking out. Be sure to check your OVP fuses.

Kevin
 

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80 280SL, 85 300SD, 87 300TD, 90 300TE 4Matic, 90 300D 2.5 Turbo, 92 300D 2.5 Turbo, 92 300TE 4Mat
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1,469 Posts
here are a few suggestions:

with the key on, make sure you are getting battery strength voltage from fuse 7;

check for continuity between X11/4 pin 5 and N30/3 pin 9, its a direct connection and you should not have any drop;

short X11/4 pins 1 & 5 for no more than 3 seconds and read impulses of 4Matic warning light;

short X11/4 pins 1 & 5 for more than 3 seconds to reset system.
 

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1991 300E 4matic
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2 Posts
Discussion Starter #4
Here is the issue: 4-matic MIL (A1e24) lights after starting engine. DTC memory cannot be read out.

Here the possible causes: 4-matic valve (up to 05/91)
4-matic hydraulic unit (A7/2)
Oil pressure switch (A7/2s1)
Oil Supply pump


Fuse 7 is ok. Tandem pump is ok. Fluid level 4-matic reservoir is full and clean. I do have some hydraulic seepage from pressure switch (A7/2s1).

I was on Electrical Test Step #6 testing the Oil Pressure sensor but ran out of free time. So thats where I'm at. If I disconnect pin 8 from x62/8 I am able to pull codes with Impulse Counter. I get code 10. I have 12 volts going to pin 8 at connector x62/8 until I plug it in. Then no voltage. Running or not, service valve on or off.

Thats all I've got until after Christmas. My guess its the sensor, but that suckers around $250 bucks. So I want to be damn sure that I'm not just throwing anymore parts at the problem.

Merry Christmas Everybody!!
 

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80 280SL, 85 300SD, 87 300TD, 90 300TE 4Matic, 90 300D 2.5 Turbo, 92 300D 2.5 Turbo, 92 300TE 4Mat
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1,469 Posts
I don't think you need a 4matic specific rear axle sensor and anyone will do.

BTW, does your set-up have the hydraulic test switch or the electronic one. I've seen only a few 91's with the older hydraulic set up and that makes a difference on which A7/2 you have, so reading out of the MY 1990 service manual could steer you wrong.

I always like to fiddle with the easiest first and not necessarily the suggested testing order. That being said, could be as simple as a stuck brake switch (S9/1).
 

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'92 300TE 4matic 280,000miles, '92 300TE 4Matic 'Ice Blue Metalic' 101,000miles
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10,399 Posts
The oil pressure switch which is actually a pressure transducer is around $300....I just replaced mine. The rear axle sensor should be testable but like most 4matic troubleshooting, info is scarce. If the 4matic valve is at fault and it's not the pressure transducer, then the other usual replaceable part is the little black accumulator screwed into the valve....they go bad as well just like its bigger cousins in the SLS. If the car is hopping a little as you park and negotiate it may be the ABS front wheel sensors.

Kevin
 
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