Gear Selector Module (W203 C Class Est. 2006) Stuck in Park

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New Member
Feb 24, 2022
West London
Hello all, I am 2nd owner 100k miles 2006 C Class Estate 1.8 Komp (W203) in UK.
This is my 2nd post. Hopefully more concise and I've had progress (kind of).

Car previously stuck in D/N and would not R/P. It stuck in P 4mths ago when I was up a high kerb. It then slipped back and worked.
So a few days ago when it stuck in P again out the blue, wobbled car, drove OK. Tapronics and auto gears fine. Dash showing the gear.
Parked up, would not go beyond N into R or into P. Had to leave key in, N and handbrake and lock it up. Couple days later, drove and parked, gear stick slipped right into R and P, didn't even try! Now it stuck in P again at a shop's secure car park (lol).
I wrote some notes below against ideas I found.
Have also ATTACHED two PDFs of the W203 manual parking lock/transmission section.
We used this to try and get ideas.

Very interesting thread (click here) on mbworld which the guy seems to have exactly what I have.
Have also attached a "C240" centre console diagram which somebody posted on there and a couple other guides someone posted there.

We've tried the override release. It does not work. When we push the brake pedal, lights work and the transmission reads it because you can see the plunger be pulled into the module when you press brake. (I have the centre console and coin holder out etc). We did try to get to the Parking lock interlock cables near the ignition lock etc. but could not find it and were pushed for time before shop shut and had to leave the car! My Dad is late 60's and doesn't do much car work anymore but we tried!

  1. Defective Brake Light Switch - NO, brake light OK and transmission reading it (
  2. Low Voltage or Dead Battery - Battery 1yr old
  3. Spilled Liquid on the shifter assembly - Potentially ?
  4. Defective shift interlock solenoid Potentially ?
  5. Faulty Engine Control Unit (ECU) or Transmission Control Unit (TCU) Potentially ? Or TCU plug?
  6. Transmission Shift Cable Broken or Shift Rod Bent / Loose Potentially ?
  7. Plates Potentially but dash is showing and electrics seem fine...?
Ideas from other threads on mbclub:
White nemesis: Quite common for the electro-plate to fail with sensor faults.
Quite common for the pilot bush connector to allow atf to travel up the loom to the ecu and kill it.
I'd recommend getting a good MB independent to have a look, STAR diagnosis will help pinpoint the issue(s).
Petrol pete: 722.6 transmission which is arguably one of the most robust of its time . As a result there is a lot of expertise on it. The place to start is check fluid level and get the codes read. If codes can be cleared and fluid level is good and it is still playing up it can be something as simple as the TCU plug on the side of the gearbox (super cheap fix) or the conductor plate (or both).

I've sourced a 2nd hand gear selector module £165+VAT delivered. £240+VAT fitting at MB specialist.
They are 20 years history, only Mercs, done my timing chain and I do somewhat trust them. I'm sure they will also check plates/wires and do gearbox oil change (I will ask).

What do you guys think? I've just had my 4 suspension arms and bearings done and 4 new tyres and tracked (plus the new timing chain last year!) 100k miles. Damn car! It's in great condition apart from all that 😅 will keep everyone updated seeing as this seems common (and bloody tricky). Any comments appreciated. I am actually an office guy, I know nothing about cars and prefer motorbikes but I've been researching! My Dad is the mechanic. He got me the book. More posting for reference seeing as this problem is a nightmare and tricky!!


  • W203manual 1of2.pdf
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  • W203manual 2of2.pdf
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  • C240 Center Console Breakdown.jpg
    C240 Center Console Breakdown.jpg
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  • Remove_install center console.pdf
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  • Adjusting wire cables for parking lock interlock.pdf
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  • Remove_install pedal assembly.pdf
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  • Remove_install electronic selector lever module (ESM).pdf
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  • Adjusting shift rod.pdf
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Also, if I do pay for this gear selector module to be installed and coded (and STAR checked of course).
I should ask him to do other things at the same time? Change oil gearbox? Check parking brake line and clips. Check battery/voltage.
Should I replace the TCU (trans. control unit) plug that plugs into the selector module? I've seen that is a cheap fix and sometimes works.
Feels mechanical as the key in any position, with brake switch activated... don't understand why won't leave park. !! Must be module?
@Neepneep, I am having the exact same problem as you describe - looking for a trustworthy and reliable MB specialist in West London, who are you using ?

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