tivoboy

Backstory… rock solid car, but hasn’t seen more than about 1000 miles in the past 4-5 years. 22.5K miles.

Been doing a bit more driving lately, but today just parked it in a garage and it would NOT DRIVE or REVERSE.. it seemed to go into R or D in the display, and felt like the transmission was engaging.. Gas made the car at least move VERY slightly rewards or forwards, but then nothing.. felt like BRAKES on, but car not moving.

No tranny issues present up to this moment. Car has been solid, and maintained, although last head to toe service was 4 years and 1200 miles ago. (I was going with a bit more mileage than years as the yardstick).

Garaged always in FLAT garage, but only difference in the past two months has been parking on a driveway that has a small slope. So, MORE engaging of parking brake than normal.

I could get the car into N for towing. Tried putting it into P and rocking, E brake on, E brake OFF - makes noise like full dis-engagement, and of course in N it rolls fine.

VERY odd, but where should one start to look for random failures that can lead to this?

W205C43PFL

First of all, a 2016 model year vehicle in 2024, the transmission fluid should had been done if not it is overdue. It is both mileage and time based. Secondly, did you get a scanner capable of reading Mercedes codes to see what the car computer is reporting back?

tivoboy

Thanks… I did transmission fluid changes about 5 years ago just before he pandemic… car was still under warranty (7 year) at the time, but figured I’d do that when I did B service..

Haven’t gotten scanner codes back from local Benz stealership.. My favorite local shop apparently closed two years ago.. ;-(.. I hoping that the $310 diagnostic charge will yield some insight of course, but can’t figure out what the stack rank of probabilities is for something to go from seemingly fully functioning to catastrophic failure in a heartbeat.

W205C43PFL

You're welcome.

Might be the aux battery, check the starter battery as well, how old is it? MBs are very sensitive to voltage changes so a weak battery could cause issues like this. If you don't want to pay for diagnostic charge, you could get a scanner, forum members here are recommending Launch CReader Elite Benz V2.0. it is cheaper than one diagnostic charge at a shop.

Especially if you plan on keeping the vehicle for a while, it is worth having a scanner.

tivoboy

Good tips..I thought MAYBE it was battery, but starting seemed fine and has been fine. Throughout 2021-2023 I started it up and drove it a bit every 60 days or so. Of course lead acid batteries DO just deteriorate.. I can’t recall if we’ve ever had to replace battery, but cranking and starting all have seemed fine as has been running. The 12v mains MIGHT have been replaced ~ 5 years ago, it would have certainly been pre pandemic period. Is there another battery other than the primary 12v?

I might look into that scanner.. sadly I had to just get it towed to the dealer as my go to place for Benz work was closed. Good tip.

W205C43PFL

Good troubleshooting steps, yup there is an aux battery, it is called a battery but it is really just a super capacitor.

tivoboy

Ouchiewonchie!!!

Well, here is what came back..

FALUT: NO TRANSMISSION POWER, TRANSMISSION VALVEBODY AND SHIFT SOLENOIDS FAULTY

REPLACE VALVEBODY AND SHIFT SOLENOIDS, CHECK TRANSMISSION FOR DAMAGE, PERFORM ADAPTATIONS


Estimate… 6.5-7K… holy mother of god.

Can this type of thing really just fail instantly without direct cause or any history at all of problem?

tivoboy

Oh, and they also say battery faulty, but that’s only $795 to replace and “reset” the system… JEZUS.

W205C43PFL

There might be another way to fix this, let me ask forum member @CaliBenzDriver for assistance.

What you are reporting is not a common issue of the 7G+ tronic transmission at all. Unless the fluid used from last fluid change was not to spec or the level was not to spec, etc.

I still recommend getting that scanner I mentioned earlier, or if not get a second opinion from a different shop or dealership.

CaliBenzDriver

(Sorry "now boarding..." not time!)
let me read this thread tomorrow
If this is "PRND" sounds like:
solderless ISM or
leaky ISM connector

For now use a SCANNER TO POKE TCU.
What's happening??

tivoboy

No worries, I’m in a holding pattern too.. safe travels… but I’ll need to try and figure out next steps by Monday 9/9… if anyone can give any insight that would be great. From what I’m been able to find here and elsewhere (repairpal among others) the solenoids themselves should NOT be too much, replacing all should be like <$1000 and labor should NOT be 20 hours worth, more like 4-5 at MOST… so something is amiss or just being jacked.

I mean, I indicated to them all the suspect issues, AND that I was ex Daimler 7+ years and BUILT the warranty tracking systems - as well as their entire business TV system… maybe that didn’t make it down to the service tech lead. ;-0

W205C43PFL

All good! Greatly appreciate you coming to the rescue, a very tricky situation for OP and hopefully you can help assist and guide him on the right track to get their vehicle back on the road again

tivoboy

I’ve been away SOO long I didn’t know there was a BAT SIGNAL!

tivoboy

Update in case anyone can offer any other insight into issues or possible pricing.

Seems they want to actually replace the transmission valve body and not just all the solenoids… that is what pushes up price and time.. the T valve body is ~3K already, then figure 600-700 for all new solenoids, and ~ 7 hours shop time (at a ridongculous $310 an hour)..

What I simply can’t understand is why literally suddenly from one minute to the next with zero prior indication. Also wonder if there is some amount of “AMG” tax on at least parts, even though this 7G has to be very close to all others.

CaliBenzDriver

Your low mileage serviced tranny decided not to shift and the local MB dealer quoted only $7k for a valve body (+ batteries swap).

Let's troubleshoot the chassis condition before quoting big tickets - That tranny itself is a really resilient unit but may easily catch upset from built-in CAN bus glitches.

I can guess you've had low voltage these cars don't tolerate well.

At this point I would use an MB compatible scanner to survey your collection of faults or go to an MB specialist for a second opinion and a more realistic quote from $500 to $2500.

tivoboy

Thanks for your response! Sadly, I missed the message reply alert over the weekend..

I would expect the transmission to be pretty solid, essentially being the AMG 63 model in this C450. Sadly, I don’t have the faults from the diagnostic that the Benz dealer did. I’m going to try and get that from them today. Since I’m paying for it, I should probably have access to it.

I can’t really get a diagnostic tool on the car in the security lot at the dealer for now. I guess my only option would be to have it towed elsewhere, my legacy go to third party mercedes service shop was closed all last week - well and they had an ownership change a couple years back so I’m uncertain as to quality.

Would having all the fault codes help to understand better or more precisely.. I mean i think that’s a duh, but for this type of things maybe more a maybe. Any thought that a better battery and system reset could prove beneficial?

I guess when the dealer says must do solenoids AND the Valve Body, that is more likely just best practice as replacing the solenoids, rebuilding, filling, testing could ultimately prove that there was a valve body problem, which would then require another purge, disassembly, R&R, re-build, etc. etc.. overall probably nearly the same cost just to try out the current tranny valve body for function.

Or, would there be an ACTUAL fault code that indicated valve body is a definite fail/fault point.?

thanks in advance!

tivoboy

So, I think the primary fault is P077800… any thoughts on that?

W205C43PFL

Hmmm if this is the same thing, you might just need a new control unit (the TCU) and not a valve body (it is a different transmission though): https://mbworld.org/forums/s-class-w...ical-code.html

tivoboy

Thanks, yes I did just stumble upon that thread a little while ago. Will have to do some further investigation. I wonder if there is a way to confirm ANY of this without just R&R the entire trans valve body and all solenoids.

W205C43PFL

Mhmm, it will be ideal that you don't have to end up replacing the valve body.

tivoboy

I guess this is some more explanation of the car fault.. I can’t really see anywhere where it indicates full trans valve body..

P077800. The internal electrical test of component 'Y3/8y5 (B1 multidisk brake control solenoid valve)' has failed.

Question though. In XENTRTY, what does first occurrence, last occurrence mean for mileage? I would think that is when a fault first and last occurred.. Some are mileages that are quite low, 5680 miles and some are well above the odometer reading of the car?

W205C43PFL

Hmmm good question I am not sure, sorry : (

Hopefully forum member CaliBenzDriver chimes in again to provide some answers.

CaliBenzDriver

Sorry I am away traveling across time zones...

The long story short is this reads like a genuine hard fault, not a low voltage temporary glitch.

> What to expect...
-- A tranny specialist needs to dump the conductor plate to replace (contaminated) solenoids.

-- At that point a complete flush is in your best interest to remove the bulk of contaminants so new-valves screens will stay clean.

-- Followed by "adaptations" retraining.
🤞

W205C43PFL

All good about the time zones hope you enjoy your trip! Greatly appreciate your expert advice hopefully that helps OP : )

tivoboy

thanks for your post..

Any thoughts if that means like real full tranny valve body replacement is either required or just best practice? I’m going to try and see if my more local legacy mercedes shop can quote me the full Monty for less than the very high cost from a direct dealership. Is that something not TOO difficult overall for a shop with transmission experience or is it really best left for the mothership?

thanks in advance, I know the time zones thing can be challenging. I did Stuttgart to NYC, and LA for many years trying to work across all nine time zones often.