2016 C450 all of a sudden won’t go into DRIVE or REVERSE?

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?
Last edited by tivoboy; Sep 4, 2024 at 07:18 PM.
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?

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.
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.
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.
Last edited by W205C43PFL; Sep 4, 2024 at 08:36 PM.

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.
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.
Last edited by tivoboy; Sep 5, 2024 at 11:04 AM.
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.

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?
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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?
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.




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.
let me read this thread tomorrow
solderless ISM or
leaky ISM connector
For now use a SCANNER TO POKE TCU.
What's happening??
Last edited by CaliBenzDriver; Sep 5, 2024 at 05:29 PM.

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

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.




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
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.
Last edited by CaliBenzDriver; Sep 6, 2024 at 07:05 PM.

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.
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!


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




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.
🤞
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.
🤞
Last edited by W205C43PFL; Sep 11, 2024 at 05:52 AM.

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.
🤞
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.


