Transmission Computer failures, What causes it?

Memphisvette

New member
I am a mechanic. I have five Tn1 Sprinters, and I have had two blowing the transmission computer . I replace them, and they run fine for a few hundred miles, then fail again. Is this a common problem? Has anyone found the cause? Can the computers be fixed?
 

lindenengineering

Well-known member
I am a mechanic. I have five Tn1 Sprinters, and I have had two blowing the transmission computer . I replace them, and they run fine for a few hundred miles, then fail again. Is this a common problem? Has anyone found the cause? Can the computers be fixed?
Well to answer your question I would say emphatically NO!
Like most solid state controllers the thing that kills them are sudden voltage spikes, reversed polarity and short downs caused by poor connections/lack of insulation and of course the age old problem of grounding--or the lack of it!

I would say the most overlooked part of the vehicle repair business either at DIY or Pro level!~

All that stated, be mindful that MB wiring harnesses/connectors are not the best in the industry (Ford has that accolade with ISO 9000 certification and the Japanese are on par with it) They are especially bad on 2002 to 2003 Tin models as they age giving rise to all sorts of driveability problems.

If you have two units that are exhibiting the same issue (theoretically at this stage) it might be time to open the TCM and study the circuit board. If it shows a distinct failure similarity then focus in on the actual circuit affected. From there you can go to say Mitchel for the wiring diagram and trace where your short or circuit mal-function might possibly be.

Yes you can get SOME solid state controllers repaired and the first company that comes to mind is Carquest . However I urge you to find the fault first before throwing yet another module at it.

As a footnote have you consulted Identifix as a Pro in the business?
When faced with a strange problem or a platform I don't work on too often (like bloody awful BMW's) its the first thing I go to?
Best of luck
Dennis
 

Memphisvette

New member
Dennis and ShortShort,
Thanks, for your input. Has anyone out there had this problem too? I wonder if a transmission solinoid that is drawing too much currant might slowly fry the board. I have looked carefully at the Trans computer boards and they have no visual defects.
Scott
 

220629

Well-known member
Are these high mileage vehicles? Have the transmissions been regularly serviced (60,000 mi. interval)? What codes are you getting?

There is a history of the speed sensors in the valve body getting contaminated with iron dust. That dust often can be cleaned to restore proper operation.

Nag1 TECH ALERT

https://sprinter-source.com/forums/showthread.php?t=2476

Note that Doktor A backed off a bit from doing the speed sensor cleaning procedure as a regular P.M. to performing the cleaning only when symptoms are present. There is some risk of causing problems when going further into the transmission than just a PM fluid/filter change.

As has been mentioned already, fluid leaking at the transmission electrical connector body, or wicking up the transmission electrical cable to the TCM can cause problems by shorting out the rather sensitive CAN bus signals.

vic
 
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lindenengineering

Well-known member
Dennis and ShortShort,
Thanks, for your input. Has anyone out there had this problem too? I wonder if a transmission solinoid that is drawing too much currant might slowly fry the board. I have looked carefully at the Trans computer boards and they have no visual defects.
Scott
Scott
Hi
I mentioned in my last post if you had access to "Indentifix"?
I use this and other Pro Mechanic "info tools" when faced with a strange problem.

Today I did a search and found one post on a similar problem which was traced to shorts in the Can Bus via the Skreem module.
If you don't have access I can either PM it to you or try to post it.
I have to do some printing off and scanning in since its all from a Pro Mechs web site.
Consists of four sheets of checks.
Let me know
Dennis
 

220629

Well-known member
Scott
Hi
I mentioned in my last post if you had access to "Indentifix"?
I use this and other Pro Mechanic "info tools" when faced with a strange problem.

Today I did a search and found one post on a similar problem which was traced to shorts in the Can Bus via the Skreem module.
If you don't have access I can either PM it to you or try to post it.
I have to do some printing off and scanning in since its all from a Pro Mechs web site.
Consists of four sheets of checks.
Let me know
Dennis
:thumbup:

Along the same train of thought.

... I have five Tn1 Sprinters, ...
That suggests fleet service. There have been a few threads here where problems with CAN bus communication/interference have been related to added aftermarket Fleet electronics such as GPS tracking.

If all the affected Sprinters have the same added aftermarket device I would also look to those.

vic
 

Memphisvette

New member
Dennis,
I would appreciate it greatly if you could post the info on the can bus here for the Benefit of all, but if that is difficult , then a PM would be Great!
Thanks!
Scott
 

wires

Member
I have had two blowing the transmission computer. I replace them, and they run fine for a few hundred miles, then fail again.
I know in the world of traditional mechanics replacing a part and having something work is a definitive diagnosis of a bad part. However in the modern world of many inputs, outputs, associated wiring and connectors that may not be the case.

I would suggest contacting S.O.S. Diagnostics or a Sprinter transmission specialist like Silver Star Transmission and see what they have to say. Hopefully they can point you in the correct direction from their experience or checking some of your "blown" units to see what is wrong with them. Most modern automotive control units are quite electrically robust so I'd be very interested in what is determined to be the problem.
 

Memphisvette

New member
I wanted to post what my final conclusions were concerning this problem with the transmission control module's. I bought several on the Internet and had the same problem over and over. Finally I got a quality scanner and took my known to be good 2006 sprinter and plugged to each module into it and clear the codes for each computer module one at a time. This restored all of them to working order. I think that some of the problem was a metallic build up on the speed sensor in the transmission. I have had some success in reducing this problem by removing the pan and cleaning the sensor magnets. So in conclusion, proper clearing of the codes helped a lot. I might add that one of my sprinters seemed to resist clearing the codes so I would have to plug the module into another sprinter that worked in order to clear it.
 

Memphisvette

New member
Well, the problem gradually came back, and got so bad that it would corrupt the transmission computer in seconds. I finally replaced the shift solinoids with a set of good used ones and that fixed it? I will report back if it fails again.
 

parallevar

2004 2500 118” High Roof
Well, the problem gradually came back, and got so bad that it would corrupt the transmission computer in seconds. I finally replaced the shift solinoids with a set of good used ones and that fixed it? I will report back if it fails again.
Do you remember the codes that you were getting for this issue?
 

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