I've had a W210 E420 1996 with the 722.6 5-speed automatic for about 4-5 months. It's allways shifted a bit hard, and a little late from 1st to 2nd on start-up when cold (ie I had to rev it a little to get into 2nd when driving down my street in the morning). After driving it a little to "tuff", with a couple of burn-outs and hard gas on corners it started shifting REALLY hard on all gears, and then the next day it seems like it was stuck in 2nd or possible 3rd gear (no torque from standstill, and no upshift even at 6-7000rpm).

After that I've gone crazy, first I bought a dip-stick and checked the fluid level which was a little high. Sucked out about a litre, but didn't help. Then I bought a kit on ebay.de with a new conductor plate, connector, filter and 7 litres of Dexron VI, changed it all, but still the same. Next I bought a iCarsoft MB 2.0 and 38-pin connector, got 13 fault codes saying stuff like Y66/1 reversing/parking lock solenoid short circuit, PWM solenoid valve intermittent fail etc. Cleared all the fault codes but still stuck in 2nd gear. Then I read a post online, and disconnected the battery and put + lead on - terminal for 30 seconds to reset. I've also tried the "key, kick-down 10 sec's, key off, release kick-down, wait 2 min's" procedure. No luck...

What's next, change more stuff? Take it to a MB authorised workshop who can clear the limpmode?

 

Once a 722.6 goes into limp mode for an electrical issue, you must use STAR/Xentry to clear the codes from the TCU after the faulty parts are replaced. PWM solenoid fail is a solid electrical issue. Don't be surprised if you need a conductor plate and solenoids (if in there once, just do them all), electrical bushing on side of transmission, and verify transmission fluid did not wick up the harness into the TCM module under the hood. Your description of the shifting could also be the TCC solenoid. Search advanced upper right corner of screen.

A hydraulic or mechanical issue will clear with a key on/off. Not so for an electrical fault.

 

Ok, great. So I proparbly have to change the parts first, then take it to a MB-shop to clear the codes?