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Discussion Starter #1
I have a C220 CDI 2003. I recently had a problem starting and found by moving the control arm from shifter to gearbox it started. Then i had the fault intermittantly and found I couldnt get reverse or park without turning off the ignition. Then reverse and park worked fine. The display was not showing which gear was selected. I have replaced the conductor plate and wiring harness socket and had the faults cleared to get me out of limp mode. today the car has no display on the dash. I released the gearshift and when cycling through the gears found the display showing only W & R (not showing D or N or P)
Any advice or help would be much appreciated
 

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It could be a problem with the AGS (gear selector) - if it is not communicating, the gear won;t display on the instrument cluster.
 

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Discussion Starter #3
Thank you for the prompt reply Rudeney

I thought from looking at gear selectors for this model that there was no electrical connections actually in the selector and that all electrical connections were from the plug into the gearbox.
Am I wrong in this assumption ? Im happy to strip the selector lever down if neccesary.
It took me a while to realise that the display was not showing any gear selected. that is the only thing that has not been altered.
When looking at selectors online I didnt see any electrical sockets. is the AGS a seperate unit in a seperate part of the car.
Any help would be greatly appreciated.
Regards Cass
P.S. is the 2003 model a W203 or W204 ?
 

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Discussion Starter #4
My Bad homework

Ive just looked again and found there are electrical connections to shifter.
 

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The AGS is in fact electrical, in addition to its mechanical linkage to the transmission. It has diagnostic codes that can be scanned with the proper tool (such as SDS).
 

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Discussion Starter #6
AGS

Thank you again Rudeney for the time.
I had the mechanic come this last Monday and Clear the car for it to drive in NON limp home mode. We drove the car round my area with his scanner attached (its a professional bit of Kit with inbuilt printer) and the car performed well with the scanner showing no faults. So this problem is intermittant.
Is it possible to dismantle the AGS to repair ? I've looked on youtube and not found any articles on my type of shifter but lots for petrol type cars.is there a difference ?
Once again thanks for youe time and attention.
Regards Cass
 

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after reading your post.. i tried looking at the dash when i used manual mode... i mean the up and down shift mode..

i'm quite sure my car comes with the 7g gear box..

when cruising.. and i push the gear selector left..

it "drops" down to gear 6... the "D" on the dash turns into number 6..

i can keep pushing left.. and it will go down to 5..4..3..2..1... (usually a noticeable jerk when dropping to 1, even at very low speeds)..

only way to make it back to "D" again, i found is to keep toggling right until going past 6, shifts back to "D".

i figured the reason why they don't show "7" is because that is the final drive that is used for cruising speeds... and it won't make sense to go to "7" if u just wanted the car to be in fully automatic "D" mode..

i can actually shift up from 1.2.3.4.5.6.D even when just going at 20km/h...

so from what i see is.. the car will drop a gear if u toggle left... but if u keep toggling right.. it will not up shift unless the current speed allows it...

haven't tried going from D.6.5.4.3.2.1 in quick succession without slowing down too much... i worry i would blow the gear box... or will the car not allow the down shift?

anyone know? hope i explained it clearly enough...
 

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Thank you again Rudeney for the time.
I had the mechanic come this last Monday and Clear the car for it to drive in NON limp home mode. We drove the car round my area with his scanner attached (its a professional bit of Kit with inbuilt printer) and the car performed well with the scanner showing no faults. So this problem is intermittant.
Is it possible to dismantle the AGS to repair ? I've looked on youtube and not found any articles on my type of shifter but lots for petrol type cars.is there a difference ?
Once again thanks for youe time and attention.
Regards Cass
Were there any error codes in the AGS or TCU? There is no official disassembly of the AGS can it can be done. I had a mechanical problem on my W163 ML and was able to fix it. The diesel uses the same AGS as the gasoline counterparts.

Thinking about this more, did you check the TCU for oil intrusion?
 

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after reading your post.. i tried looking at the dash when i used manual mode... i mean the up and down shift mode..

i'm quite sure my car comes with the 7g gear box..

when cruising.. and i push the gear selector left..

it "drops" down to gear 6... the "D" on the dash turns into number 6..

i can keep pushing left.. and it will go down to 5..4..3..2..1... (usually a noticeable jerk when dropping to 1, even at very low speeds)..

only way to make it back to "D" again, i found is to keep toggling right until going past 6, shifts back to "D".

i figured the reason why they don't show "7" is because that is the final drive that is used for cruising speeds... and it won't make sense to go to "7" if u just wanted the car to be in fully automatic "D" mode..

i can actually shift up from 1.2.3.4.5.6.D even when just going at 20km/h...

so from what i see is.. the car will drop a gear if u toggle left... but if u keep toggling right.. it will not up shift unless the current speed allows it...

haven't tried going from D.6.5.4.3.2.1 in quick succession without slowing down too much... i worry i would blow the gear box... or will the car not allow the down shift?

anyone know? hope i explained it clearly enough...
In the OP's case, his car has a fault in either the TCU or AGS that is causing the system not to communicate, and therefore it won't show the selected gear in the MFD on the cluster.

The TCU is smart enough to not allow a downshift that would over-rev the engine or harm it. Also, the gear shown on the MFD when in "manual" mode (i.e. using the TouchShift to select a gear) is not the "current" gear but the "maximum allowed" gear. Tapping the TouchShift left and right actually does two things - request a gear change form the transmission, and also changes the maximum gear allowed.
 

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Discussion Starter #10
TCM

Thanks again for your reply Rudeney.
By TCM and ingress of oil do you mean the plug and socket into the gearbox itself ? And yes that socket was changed as the first thing.
I ask because looking at other threads I have found there is a TCM under the floor om my drivers side i.e. the right side ?
A question though. If I changed the AGS for one bought online would i need it to be recoded to my car ?
Waiting for my pension before able to see about towing the merc dealer or would my mechanic be able to read it ?. He was the one to clear the codes when I changed the conductor plate.
 

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Yes, the pilot bushing seal on the transmission electrical connector leaks and oil can wick (siphon through the wires) into the TCU, which is located under the front passenger foot well. You might check that - pull the carpet down from under the dash, remove the foam insulator panel, and the TCU is attached to the back side of the metal panel.

I see no mention in SDS of any coding necessary when replacing the AGS.
 

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Discussion Starter #12
Wow ! another prompt reply Thank you,
I'll be under the carpet first thing tomorrow.
I bow to your expertise.
Regards Cass
 

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Discussion Starter #13
Incidently you said front passenger footwell on left side. Is it not on the right ? forgive my ignorance but a thread i read said ALL W203 and All W211 models were on the passenger side which for american and european is the right side
 

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Actually, I didn't specify left or right. The TCU is always under the front passenger side footwell, which is on the left side for RHD (UK) cars, and right side for LHD (USA) cars.
 

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Discussion Starter #15
Once again your experience is invaluable.
Many thanks,
Regards Cass.
I'll crack a fosters in salute to you over dinner tonight. L O L
 

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after reading your post.. i tried looking at the dash when i used manual mode... i mean the up and down shift mode..

i'm quite sure my car comes with the 7g gear box..

when cruising.. and i push the gear selector left..

it "drops" down to gear 6... the "D" on the dash turns into number 6..

i can keep pushing left.. and it will go down to 5..4..3..2..1... (usually a noticeable jerk when dropping to 1, even at very low speeds)..

only way to make it back to "D" again, i found is to keep toggling right until going past 6, shifts back to "D".

i figured the reason why they don't show "7" is because that is the final drive that is used for cruising speeds... and it won't make sense to go to "7" if u just wanted the car to be in fully automatic "D" mode..

i can actually shift up from 1.2.3.4.5.6.D even when just going at 20km/h...

so from what i see is.. the car will drop a gear if u toggle left... but if u keep toggling right.. it will not up shift unless the current speed allows it...

haven't tried going from D.6.5.4.3.2.1 in quick succession without slowing down too much... i worry i would blow the gear box... or will the car not allow the down shift?

anyone know? hope i explained it clearly enough...
The car will not allow a downshift if the speed is too fast. It will put strain on the transmission all the same.
It will also upshift if the engine speed is too high even when restricted.
 

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Discussion Starter #17
Rudeney ! You were right again. I took up the carpet on passenger side and immediately saw some oil. By the time I stripped it all out and soaked up all the transmission fluid and got to the TCM there must have been about 1/4 litre. More like syphoning than wicking. Just got some cleaner and will clean up connectors etc tomorrow. It seems to have wicked through the wires, up to TCM, then overspilled back down the wiring loom, Thank you for your advice.
P.S. That Fosters was good
 

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It's a common problem. Search the forum - I think there have been some success stories on repairing this by cleaning the TCU and wiring.
 

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I hope that Fosters was nice and cold Cass.

We colonials don't even drink the stuff anymore, just send on to our Imperial leaders.
 

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Discussion Starter #20
L O L to the fosters !
Rudeney, I cleaned the wiring and TCU still same problem. Put the TCU back clean ne relaid carpet the took of the centre console and Disconnected the AGS which i have now apart. Now the frustrating part ! all the electronics are in a box that has small allen screws. I have down to 1.5mm n its just to big. Must be 1.25mm Ill try filing down a key but need more light to see as its so small. Ill try again thursday. I think its time for a well earned Fosters.
Regards Cass
 
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