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changed transmission fluid, drove car, engine light came on and now in limp mode

30K views 85 replies 18 participants last post by  blue_devil 
#1 ·
I changed the transmission fluid and filter in my car. I followed the write-ups on this form but I used a dipstick that I got off Amazon that's supposed to be for these cars with the 6.1L. The tip was not user friendly. So when I put in the amount of fluid I thought was correct and went out to drive the car it initially shifted fine but seemed like it wouldn't go into overdrive. After I quickly realized that it wasn't shifting into the last gear I turned around to head back to the house. It was around this time the engine light or CEL came on and the car acted like I had put it in neutral until my speed got down to about 20 mph. Then it continued driving but no matter how far I depress the throttle it only goes about 20 mph. It reminds me of limp mode in my old 2000 323 BMW.

So I bought the Dorman dipstick everyone on this forum says to get and went back through my process. It looked like I was a little low on fluid but not by much. At temp the new dipstick showed about 60 mm. So I added fluid until I got to the proper level. But the CEL never went off and the limp mode or drivability issue did not change.

Any thoughts? I did the ignition key dance to see if any codes display but it did not show any. How can I clear the CEL without a scan tool?
 
#42 ·
I don't believe anyone has suggested the TCM is a fault. However it is the brains; as such if it has (electrically) failed internally, then yes it could be root cause. There is a plethora of potential root cause, everything from shift solenoids, trans PCB, connector interface, etcetera...
 
#43 ·
I know when I changed the crank sensor on my 8.1L Suburban, it required a "crank re-learn" for the PCM that could only be done with a GM scan tool. Apparently the sensor readings are very exact and the re-learn matches the sensor to the PCM so it knows exactly where the crank is. Kind of like tapping around a tablet with a stylus to calibrate a touch screen. It's possible that failure to do a re-learn on the PCM could be causing a code in the TCM for some reason. Just speculating here, but the new crank sensor certainly adds a variable to the equation. Unfortunately in my experience, you can't just bring your car in and ask the dealer to do a specific task, they list everything coming in as needing diagnostics to see what the problem is. Ideally a dealer scan would show the need for a crank re-learn and hopefully clear up the TCM code at the same time.
 
#44 ·
A / any P0300 Random Misfire is a PCM-driven DTC and unrelated to TCM operation :^)
 
#45 ·
Posts like this make me laugh. You could have easily taken it to a dealer by now. Paid 125 bucks for them to properly check your fluid and run a dtc check and be done with it. If this issue occurred POST service. You’ve done something wrong or cause something with whatever you did.


Maybe I’m wrong.

But I guess what do I know. I’ve been certified for 11 years with Chrysler and work for a “stealership ” as you call them.

You’d think being an engineer you’d have figured it out by now :)






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#77 · (Edited)
Posts like this make me laugh. You could have easily taken it to a dealer by now. Paid 125 bucks for them to properly check your fluid and run a dtc check and be done with it. If this issue occurred POST service. You've done something wrong or cause something with whatever you did.

Maybe I'm wrong.

But I guess what do I know. I've been certified for 11 years with Chrysler and work for a "stealership " as you call them.

You'd think being an engineer you'd have figured it out by now :)

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Because you mentioned your a certified Chrysler tech... Have you ever heard of or experienced this issue when removing the 7mm bolt on the Guide Bushing? While doing research relating to valve body overhauls, I saw this in the comment section on YouTube, video (Here's Why Lifetime Transmission Fluid Is A Total Scam & How I Restored My Trans For Cheap. DIY!).

David Lanco
"The transmission electrical connector housing on the 722.6 should be replaced when it is COLD! (Check wis) if you remove the electrical connector housing when it is hot you will strip out the conductor plate.... replacing the electrical connector also prevents transmission fluid entering the transmission control unit. Most people don't know about this issue. Btw great videos! I too am a former MB dealer tech, I now work for MB vans in South Carolina . The 722.6 has been a better transmission than the 722.9, the dot 9 was never user friendly outside the dealer. Btw you forgot to mention using the dipstick tool for the .6 since the .6 never had an actual dipstick. I own a 1997,1998, and 1999 e300s...the 1997 has been a bit troublesome compared to the 98 and 99. Stay away from 1997 non turbodiesels the parts are more expensive than the 98 and 99"

I asked him the following...
"I had the 13-pin plug (Guide Bushing) leak on my Nag1 (Dodge Magnum 06), known issue. I took it to the dealership to get the new one installed. The tech said he couldn't remove the bolt holding the GB, it was stripped & spinning. Said I needed a new ECM/ conductor plate. Is it possible he didn't know (it was hot) and he spun the bolt and pressed threaded fastener in the ECM?! Mistakes happen... I'm doing this job here in the video tomorrow, including new ECM & TCC Solenoid."

Thanks in advance!
 
#46 ·
@hemissary, you obviously know more about this than I do, I was just wondering that given how close the TCM and PCM operate, if the TCM would throw a code and go into limp mode based on the presence of certain codes in the PCM.@jerrytotin, that would have been my play, but sounds like OP is a hard core DIY and determined to fix this on his own.Was wondering there was any update from the OP on if/how he solved the issues.
 
#48 ·
I almost never do this sort of thing, but I threw out the old connector before actually checking operations. :doh: I did however ensure the new connector visually matched the o.g. and I verified the installation of the connector. I've taken it out and put it back in 3 different times now trying to reassure myself of orientation and seated depth.

I've not been back working at this for a bit, but had anyone tried dielectric grease on this connector?
 
#49 ·
A few days ago I checked continuity of the pins from the female connector where it plugs into the transmission to the connectors at the TCM. All good. Checked cleanliness. All good. Checked for shorts. All good.

For the 2nd time I sucked the fluid out and dropped the pan. Fluid, pan, filter, all still looked good. Dropped the valve body for an inspection of the solenoids, speed sensors, and conductor plate. Everything visually looked good. The solenoids checked out okay so far as resistance. I did this just because I had it down to this part anyway. No muck, shavings, or anything.

Reinstalled the valvebody. Installed yet another new electrical transmission connector just for good measure. This is the 2nd new one, bought it from Dodge. Installed new fluid for the 3rd time now. Used my Dorman dipstick, Torque Pro and my OBDII bluetooth transmitter to verify the transmission temp and fluid level.

Drove the car. Same issue, same code thrown. :banghead: Shift fine in rev, 1, 2, 3 and shifts into 4th fine, but after about 2-3 seconds it shifts back down to 3rd and throws the P0730 incorrect gear selected code. Doesn't matter if I leave it in D and let is shift itself or if I shift through the gears manually.

So now what? Replace the TCM? Go to the dealership and hope they don't shoot me a line of bull?
 
#52 ·
Also, oem crank sensor?

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Funny you should mention the Crank Sensor. No, I replaced it at the same time as when I originally did the fluid / filter change. I replaced it with one from AutoZone. I figured while I had the car up I'd go ahead and replace it. I did it because for the last couple of years, randomly but not often, the car would not start or sometimes when running, when I'd slow down to a stop light or the like it would die on me. The CEL would come one. I had it scanned a couple of times and each time it was the same code. I don't remember what the code was but it suggested to change out the crank sensor. Since you had to remove the starter to do I, and it didn't happen often I just let it go until like I stated a moment ago, I had the car up to do the fluid / filter change.

I haven't given the crank sensor any thought because I didn't see how it would effect the situation. Given all I've done and that's a variable that changed from when it was fine and now its not, I think I might re-install the original one, since I kept it, and see what happens.

Does the crank sensor play into this code?
 
#53 ·
It’s not directly related to your code. But these cars are fickle bitches about the electrical so who knows. Oem is the way to go for sensors. I’m not aware if the tcm gets any signal from the crank I believe on some other cars it does.

I’m betting your conductor plate went bad for whatever reason, that’s where the transmission speed sensor is.

I’m not one to throw parts at a problem but if your gonna go for it I believe it’s about 150$, be sure to get a genuine Mercedes part


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#57 ·
:banghead::banghead: I changed out my conductor plate. While I had the solenoids out I used my Fluke multimeter to check their ohms across their terminals. All looked to be okay.

No change. Still have the same issue. Goes into 4th, then after a second or two it shifts back down to 3rd and throws the P0730 code.
 
#58 ·
At the risk of a repeat...

Throwing parts at it ninety-nine times out of a hundred never solves the problem (especially electronics). It does however - empty pockets...
 
#59 ·
I know, I know. I'm a controls engineer and I've been working on cars (hobby) for 30 years. Usually that's not me. I try to approach things logically and gather a ton of info. I found and downloaded a pdf of the service manual, something like 10,000 pages worth. I've studied the P0730 code and info pertaining to it. I've done all kinds of troubleshooting " and parts thowing ". Just don't know whats up. How can it be working, do maintenance, and now not work.

I'm thinking of taking JD323 up on his offer a few posts back. I'm just not sure what the difference is between that TCM and my TCM. Mine has a PN# of P04692392AG and his has a pn# of P04692392AI. Same except for the last letter. Mine has a "G" and his has an "I"
 
#64 ·
A HUGE THANK YOU for the kindness give by JD323! Unfortunately that TCM did not change / fix my problem. That TCM worked, but worked just like my factory unit did; same issue remains.

Very puzzling. It looks like I'll be making an appointment with a Dodge dealership to look at it and hopefully they are straight-up with me.
 
#67 ·
:chickdance: Rebuilt my valvebody. Fixed my issue.

After a lot of logical troubleshooting, internet research, scouring forums, using the 9500 page LX Platform service manual for guidance, and part replacement, it turns out that rebuilding my valvebody was the fix.

I pulled it out and broke it down to the base parts. Cleaned the parts with brake cleaner and compressed air. Then lubed up all the valves, springs, check balls, and screens with tranny fluid as I reinstalled everything. I also installed the Sonnax Overlap Control Valve Sleeve Kit and the Sonnax TCC Damper Valve Sleeve Kit. Got everything reinstalled. Worked like a charm.
 
#68 ·
:chickdance: Rebuilt my valvebody. Fixed my issue.

After a lot of logical troubleshooting, internet research, scouring forums, using the 9500 page LX Platform service manual for guidance, and part replacement, it turns out that rebuilding my valvebody was the fix.

I pulled it out and broke it down to the base parts. Cleaned the parts with brake cleaner and compressed air. Then lubed up all the valves, springs, check balls, and screens with tranny fluid as I reinstalled everything. I also installed the Sonnax Overlap Control Valve Sleeve Kit and the Sonnax TCC Damper Valve Sleeve Kit. Got everything reinstalled. Worked like a charm.
Good job; what was root cause?
 
#69 ·
Hey, go see the dealer.

You'll spend more time and money chasing this thing down and maybe fouling things up in the process. If my experience any anything like normal, you'll bring it in, tell them what's misbehaving. The writer will tell you go into the lounge, have some coffee, read the paper a bit. When all is squared away, the writer will come back in, hand you the keys and your good to go.
 
#70 ·
Hey, go see the dealer.

You'll spend more time and money chasing this thing down and maybe fouling things up in the process. If my experience any anything like normal, you'll bring it in, tell them what's misbehaving. The writer will tell you go into the lounge, have some coffee, read the paper a bit. When all is squared away, the writer will come back in, hand you the keys and your good to go.
Yeah you keep believing that bud.

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#71 ·
Nicely done. I had a cop car with a Nag - stopped moving. No rev or drive. Our hotline said something was broke in gear train.I didnt believe that. Pulled apart and all was mint. Valve body fixed it. There are no pressure ports to measure pump output. They also told me to isolate the electrical side by starting it upand disconnecting the connector at trans. They said I should have 3rd gear default and manual reverse. Bull- I found out a nag needs electrical power to operate. There is no manual valve movement for hydrualics
 
#73 ·
Yeah this is reality, you go to the dealer and tell them what it’s doing. They drive it and hook it to their computer, tell you they can’t replicate the issue, you go with them and point it out, they tell you it’s normal, they bill you for 150$ and you still have the same problem, you go home and come here and we tell you what to check, you go back to the dealer and suggest it to them, they tell you no it’s a different part, you opt to go ahead and replace the part they suggest and they bill you 600$, you drive home and the problem is still there, then you go back to the dealer and try unsuccessfully to get your money back, then you come here again and we figure it out together, then you replace the broken part for 100$ yourself and tell us your story about the stealership.


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#74 ·
Yeah this is reality, you go to the dealer and tell them what it's doing. They drive it and hook it to their computer, tell you they can't replicate the issue, you go with them and point it out, they tell you it's normal, they bill you for 150$ and you still have the same problem, you go home and come here and we tell you what to check, you go back to the dealer and suggest it to them, they tell you no it's a different part, you opt to go ahead and replace the part they suggest and they bill you 600$, you drive home and the problem is still there, then you go back to the dealer and try unsuccessfully to get your money back, then you come here again and we figure it out together, then you replace the broken part for 100$ yourself and tell us your story about the stealership.

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Textbook stealership right there !!! Right on the head...

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#75 ·
This thread has me worried. About the dealership....Im looking into just servicing my transmission and it doesnt look promising as far as putting faith in the dealer. I wouldnt attempt to change it myself because its a multi step process where you have to pay strict attention to detail or wind up like OP's problems.

I guess the ONLY saving grace is that if the dealer screws up, I have the upper hand on them making it right.
 
#76 ·
The NAG doesn't come with a dip stick because they don't want you checking the fluid and risk getting ANY impurities into the transmission. The NAG is very sensitive to the slightest bit of rag lint, dirt, etc. that you might get in there, which will screw up the trans operation. My guess is the OP got some lint in there during his service, which got stuck in the valve body. I'm really curious where he got the notion to rebuild the valve body. Possibly he took it to the dealer and THEY rebuilt it and now he is taking credit for the fix? He seems to have a lot of pride and I don't know that he would admit the dealer fixed his screw up?
 
#78 · (Edited)
Jerry will chime in I'm sure with similar sentiments...

The 7mm brass bolt is being threaded into a brass nutsert embeded in plastic. Hot extruded plastic - obviously is going to be more maleable than cold plastics. I can see how the idea of only performing the work while the parts are cold can be made into a mandatory requirement. On the other hand, I misses the mark about the actual process that is dislodging the nutsert in the first place! Too much torque.

Therefore...any use of ratchet tools that make it easy to multiply torque is a big no-no. R&Ring this particular bolt should only be removed and tightened with either a 1/4" or 3/8" extension using a proper 7mm socket. No ratchets, no 1/4" screwdrivers, only the diameter of those 1/4" or 3/8" drive extensions with light finger pressure. The bolt does not(!) have to be tightened - beyond the first hint(!) it has secured the connector housing. Even if it was slightly loose...it is not going to affect it's ability to prevent the housing from shifting.

If it does become stripped, there are simple ways of solving this - without having to replace the conductor plate...

Finese...no brute force
 
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#79 ·
Any help... Anyone!?

So the tech was correct, telling me the 7mm bolt is just spinning in place and the guide bushing cannot be removed. A person on BenzWorld forum explains it fairly well. I was led there after searching Google for a solution. "Update: I cut a pie shaped piece out of the old connector plug with a dremel and with the valve body loosened and supported by a jack, took large socket and brass hammer and pushed the plug through the trans housing. THe conductor plate was destroyed by the process but I needed to probably replace it anyways.

Looking at the old conductor plate it is clear that the brass female fitting just spins in place in the back of the conductor plate which is why it would not come out. For the record, I tried prying it out several ways but could not get the brass screw to bust loose."

So, I am looking for advice here. I do not want to Dremel anything. I tried pulling on the guide bushing lip with pliers but pieces keep cracking off! Argggg!!!
 
#80 ·

Are you referring to the Adaptor Sleeve?
 
#81 · (Edited)
Yes. I also refer to it as the Guide Bushing, per the Service Information manual. The female threaded nut-fastner in the ECM is spinning. The bolt and guide bushing will not release. It's possible someone installed the 7mm bolt with a 1/2" breaker bar!
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