hrctoys

So I replaced the kick down switch and the pedal with new components from FCP
throttle works great, if step on it 90% it does down shift but the minute I hit the kick down switch the car enters limp mode

thoughts?

Tom Manning

Something misaligned in there. I guess that the new after-market part is not up to the job.

As the old pedal wears, the sensor inside overshoots on WOT, sending an out of range signal and putting the car into limp mode.

Can you modify either the old pedal, or the new one, so it operates the WOT switch, but prevents the pedal from travelling past its defined range? Mine has done this once, but I haven't yet pulled it out to see if I can modify it to compensate for the wear.

hrctoys

mm they are all genuine Mercedes components the same that came with the car

Tom Manning

Did you have any codes initially - the P0123 code?

Did you get the ESP light when it went into limp initially? Limp plus ESP light means it probably was your pedal. That's what happened toe me, but I only got the ESP message once, but the limp mode twice.

But strange that the new pedal gives the same issue. If you have STAR you can monitor the voltage on the sensor which should be 4.8 Volts.

MikeJ65

Was it a new pedal? Yery common issue so used can easily be bad. Is this a very early car with an actual lockdown switch or later one with simulated switch?

hrctoys

Interesting you said that. The pedal FCP sent me came with a simulated switch. I have a very early Mercedes with an actual switch that has a 2 pin Switch, not even the 4 pin switch that every part verifier kept forcing.

I took out the simulated switch and replaced it with the new 2 pin switch

MikeJ65

I'm wondering if someone changed the coding to the 'virtual' kickdown or if the early pedal had different position sensors. You might try with the switch disconnected or removed from the pedal. Check codes if you can. I think only the first 10-15k were built with actual kickdown switch and very few made it to the US.

hrctoys

son of a *****

I just reset the CELs but got a p0123 and p0223

MikeJ65

Just speculating, but I'm thinking that you have something not compatible. Pedal is wrong, ECU is coded for no switch, etc. Does the pedal p/n match what is in EPC for your VIN?

hrctoys

according to FCPs filter it does

hrctoys

ok so I checked my old pedal, the part number is:

A2303000004

and the one FCP's filters referenced is:

A2303000104

this one came with a plastic switch that did nothing

so tonight, I'm going to try to put the old pedal back with new 2 position switch, earlier I tried the FCP pedal disconnected (which should simulate the simulated switch) but that still resulted in limp mode

hrctoys

Quick update….

So problem finally solved and in the end had nothing to do with the pedal or the kick down switch.

After trying every permutation of original pedal, new pedal (incorrect part #) and new pedal (correct part #) and swapping kick down switches from each one - it ultimately ended up being a battery problem. 2 new batteries from Mercedes later, the car is doing better.
-alarm
-DTR
-trunk soft close
-parking sensors
…all began functioning normally and predictably

What set me on this course, is that finally after repeated trial errors of the pedals, I finally kicked off a CEL. I was out so I stopped by my friends shop and scanned the codes to find a whole bunch of low voltage codes, however the car would start all the time. However, the dash would give a litany of error messages from Consumer Electronics offline, DTR unavailable, boot lid not closed, etc. The both batteries were replaced in late 2018 and are factory Mercedes genuine batteries. I thought just under 5 years for batteries - no way! My Porsche factory battery went 7 before I replaced it with a Li-Ion and my Honda and Toyota batteries went 9 before being replaced!

After $500 worth of starter and consumer electronics batteries, the car seems to be running more like it’s suppose to.