w210 e300 gear recognition switch replacement pdf? - PeachParts Mercedes-Benz Forum

diesellover 92 · #1 10-23-2017, 07:51 AM

So I noticed that the transmission doesn't want to shift out of first until the engine is warmed up. I can manually select other gears but it will hold first. I already dropped the valvebody and inspected. Found a several threads talking about this being symptom of the gear selector computer. Then I read it has specific replacement procedure for adjustment. Anyone have the pdf?

jay_bob · #2 10-23-2017, 09:07 PM

I have done it:

Shifter wood panel lifts off, (open cup holder and grab edge of panel) unplug switches from underneath.
Unplug two cables from back side of shifter box. The one with the 10 wires the connector has no locking tab, just find the handle on the connector and pull back.
The two wire connector has a little friction nub but just pulls out too.
Now remove the 4 Allen bolts and pull up the shifter. It will still be attached to the transmission actuator arm.

Get a piece of string and tie it off to something inside the car.
Undo the clip holding the shifter to the linkage. Be careful it can fly away.
Tie the string to the end of the transmission linkage, otherwise if you let go it will fall down into the hole and you'll be going underneath to find it.

Bring the shifter to a work table.
Take the knob off by rotating the collar at the bottom of the knob a quarter turn until it's loose then pull the knob off.
Carefully release the 4 clips holding the upper part of the housing to the main part of the housing. I cut strips out of a plastic yogurt container to use as shims to keep the clips released after prying them up.
Lift off the top of the shifter. You will now see a white cartridge with LEDs on top. This is your gear selector switch.

Carefully pull this cartridge up to remove it from the shifter housing.

The switch can be disassembled and cleaned. Not terribly difficult, but watch out for the spring on the lever that detects the W/S switch knob on the plate.

When putting it back together notice there is a hole on the side of the switch with an R next to it. You want to rotate the actuator inside the switch so that the white dot shows up next to the R. And of course you want the lever in the R position. This is so that the actuator finger in the mechanism finds the right place in the switch cartridge.

That is how to fix the range recognition switch. However there is another problem with these transmissions.

The connector that plugs into the transmission is notorious for leaking fluid. That fluid wicks up the cable harness and gets into the transmission computer that is in the box at the right rear corner of the engine compartment. The fluid itself is not conductive but the graphite particles shed from the friction disks, suspended in the fluid, is conductive.

The transmission computer can be disassembled and cleaned. And the root cause, the plug connector at the transmission, is a well known fix. Best to search for a YouTube on this (look for 722.6 transmission) as the plug has a trick to disconnect it that is better shown visually.

Worst case scenario is you have fried the transmission computer. Unfortunately you can't go get another one from a junk yard because these get married to the VIN at the factory. If you try to plug in another one it will not allow it to work because the VIN in the other devices on the network won't match.

So here is what I would do.

First I would try cleaning the range switch, in case someone spilled a drink in it.
Then I would inspect the computer under the hood, and make sure no fluid got in it.

If both of these are clear then I would invest in an hour of shop time at the dealer and have them pull the codes for you to see where the problem is. Their computer can see things that are not visible in the OBDII port. The transmission has pretty comprehensive diagnostics but they are only accessible with the proprietary MB computer through the 38 pin port under the hood.