I have a 2006 s55 amg. Recently after vigorous driving, transmission wouldn't shift above 3rd gear and a fault message on the dash said presafe not available. I shut the car off and after a few minutes all seemed good with gentle driving. This happened again and check engine light came on. OBD said i need a new conductor plate. Could just a clogged filter cause this? It is shifting fine now using light acceleration..

It sounds like your shifting issues could indeed be related to the conductor plate in your transmission. The symptoms—transmission not shifting above 3rd gear, coupled with a fault message and intermittent behavior after restarting the car—are classic signs of conductor plate problems in Mercedes-Benz vehicles. The conductor plate houses the transmission control module and can be susceptible to wear or electronic faults over time, especially in high-performance models like the S55 AMG. While a clogged transmission filter can restrict fluid flow and potentially cause similar symptoms, it typically wouldn't lead to electronic fault messages like "presafe not available." I recommend running a full system scan using a diagnostic tool capable of accessing the transmission control module and other relevant systems. There should be fault codes stored that will pinpoint the exact issue. Given the indications from your OBD scan suggesting a new conductor plate, this diagnosis aligns with the symptoms you've described. If you're comfortable with DIY repairs, acquiring a full system scanner like the youcanic full system scanner can help diagnose and confirm the issue before proceeding with any repairs. Otherwise, consulting a mechanic experienced with Mercedes-Benz transmissions would be prudent.

Jim,
Thank you for your thoughtful reply. I am a DIYer so maybe the next step is the scanner you recommend.

The conductor plate is a feasible answer that many of us have had to do in the past. It’s not too expensive even from an Indy. Plenty of videos online of the repair and what you should do while in there such as solenoids or the transmission connector seal bung. Like anything, we would probably recommend oem even though it’s slightly more money.

Not on this car.

if i replace the conductor plate, will i have to reset the codes too or will it behave normally after it is replaced?