*HELP* 722.9 Gearbox Problems :( Experts Required

[RAJ55]

Hi All,

Im experiencing some really odd problems with my gearbox. Car is a 2009 facelift R230 SL350, 33k miles.

Problems im experiencing:

1. When cruising on the motorway or during a long drive (in either C or S mode and at 50mph+) the gearbox will randomly downshift to 3rd or 4th gear and gets stuck in this gear until the cars engine is restarted. Trying to upshift on the steering wheel paddles or using the gear lever (nudging it to right) does nothing.


2. When driving in C or S mode, if I decide to use the steering wheel paddles, both - & + paddles only DOWNSHIFT the gearbox. If I try upshift using the + paddle, it actually downshifts the box again (nudging the gear lever left or right works fine and will select any gear I want).


3. When driving in M mode, both - & + paddles only UPSHIFT the gearbox. If i try downshifting using the – paddle, it just upshifts again (nudging the gear lever left or right works fine and will select any gear I want).


Its really strange behaviour, which im unable to pin point.

What ive done so far:
1. Transmission faults read on Star C3 – No faults found!
2. Faults read on the gear selector, steering column, paddles etc – No faults found!
3. Switched the steering wheel with another I had to see if it was the paddles – No change!
4. Checked the paddle connectors are in the correct connections in the back of the airbag, they can only go in one place.
5. Reset all gearbox adaptations – No change
6. Switched the throttle pedal with another one – No change!

Any gearbox experts on here who can advise me on my next move please?

 

[whitenemesis]

I'm certainly no expert but it sounds like the box is going into limp mode, resetting on IGN being cycled. Classic symptoms of the conductor plate sensor(s) failing.

 

[RAJ55]

Yes, from what ive been reading it seem the conductor plate and valve bodies are problematic on these boxes.

Ive ordered a new service kit for it so will try fresh fluid and filter so see if that helps, maybe its low. After that ill try the conductor route but my star diagnostics is not showing any codes which seems worrying or maybe im looking in the wrong area.

i also switched the SCM (steering control module) from my other SL but that didnt help with the paddles having a mind of their own.

 

[RAJ55]

SOLVED

Hi all, i finally got this issue fixed. For those interested and for future reference it turned out to be a faulty steering control module (SCM-N80).

I initially changed the clock spring contact (CSC-A45) thinking it was the SCM but in fact it wasn't. The SCM is actually located behind the clock spring.

How i knew the SCM was faulty was when in Star Diagnostics, under control units>body>transmission>actual values>push buttons & switches, the negative paddle was showing 'Operated' when it wasn't being pressed. A new SCM fixed the issue and the car is back to normal and is a pleasure to drive again.

Raj