1999 C43 Auto Gearbox in limp mode

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Richcourt

New Member
Joined
Apr 1, 2024
Messages
6
Location
Somerset
Car
1999 C43 Estate
Hi there, new to the forum so hopefully I’m posting in right place…. I have a 1999 C43 Estate. Recently changed auto gearbox filter and fluid and O ring for electrical connector. Ever since gearbox has been in limp home mode. Unable to connect to any modules via the 32 pin connector. Have tried Autel & Snap on. Both work perfectly on other Mercs.Have checked and have power to pins 2 & 3 and a good earth on diagnostic socket. Any suggestions please?
 
Have you replaced the conductor plate?
 
Hi there, new to the forum so hopefully I’m posting in right place…. I have a 1999 C43 Estate. Recently changed auto gearbox filter and fluid and O ring for electrical connector. Ever since gearbox has been in limp home mode. Unable to connect to any modules via the 32 pin connector. Have tried Autel & Snap on. Both work perfectly on other Mercs.Have checked and have power to pins 2 & 3 and a good earth on diagnostic socket. Any suggestions please?
As it was fine before then it is almost certainly something that happened during the service.

As said, check the electrical connector or replace it. They are under £30.
 
As it was fine before then it is almost certainly something that happened during the service.

As said, check the electrical connector or replace it. They are under £30.
Thank you for the reply. Any suggestions as to where to purchase from please?
 
I haven’t because I’d rather identify the problem rather than just start chucking new parts at it…..


You seek for advice I give you info free of charge.
You're most welcome..

Known wearNtear parts which goes bad on these cars are:
Tranny fluid.
Oil plug.
Conductor plate.

Or the solenoids, clutch packs or the tranny (sun gear) it self blows up on high mileage cars???

A worn oxygen sensor could also cause erratic shifting
 
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I haven’t because I’d rather identify the problem rather than just start chucking new parts at it…..
A very6good approach. Parts darts is rarely successful but considering the age of the transmission a new electrical plug at under £20 may be a wise investment 👍
 
You seek for advice I give you info free of charge.
You're most welcome..

Known wearNtear parts which goes bad on these cars are:
Tranny fluid.
Oil plug.
Conductor plate.

Or the solenoids, clutch packs or the tranny (sun gear) it self blows up on high mileage cars???

A worn oxygen sensor could also cause erratic shifting
All potentialy true but the problem was evident only after the transmission service so unlikely to be an O2 sensor.
Incorrect fluid level or a damaged plug seems to be the first call.
 
All potentialy true but the problem was evident only after the transmission service so unlikely to be an O2 sensor.
Incorrect fluid level or a damaged plug seems to be the first call.

The other stuff I mentioned was for free if OP didn't know about them?
It's good to have them in mind.
I forgot to mention, when it comes to tranny failure it's the brass bearings on sun gear on early 98-99 cars, this was improved on later C43's.

Did OP service tranny him self, perhaps he didn't follow the correct procedure and therefore got another problem after?
 
Worth checking the conductor plate for bent pins if you're taking the gearbox plug back out again. Very easy to do when reinstalling the socket if you've had it out to do the o-rings.
 
Thought I’d update this. Replaced the pilot bush, bought a Icarsoft that connected to car and cleared fault codes and all good. Thank you for all your help.
 

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