TCM on Allison Transmission needed replacing. Why?

[bluebarry1964b]

The computer on my Allison 2000 transmission (2003 Holiday Rambler Neptune) just blew. Mechanic said he only found one code on it that indicated "low voltage." He asked if I'd had battery problems. I hadn't. However, now that I think about it, I have the RV in storage right now, so I've been turning off the battery cut-off switches for both the house and engine batteries. I'm talking about the switches located in the battery compartment. I've been doing this as an anti-theft/ anti-fire precaution. I have been turning the switches back on every month when I take the RV out for a drive to exercise the transmission, brakes, etc. Then I turn the switches off again for another month. Could turning these switches on and off be the cause of the TCM frying? I'm concerned because it cost me $2,000 dollars to fix and if I don't know what caused the TCM to fry, then what's stopping it from happening again? Any ideas as to how to keep this from happening again? Crazy thing is the RV, although it is a 2003, only has 40,000 miles on it. Allison mechanic said he's seen the TCM's last 700,000 miles. I'd like to know why mine fried so prematurely.

[tenn_vol_]

I use trickle chargers on my RV and both motorcycles.
A low battery or a BAD GROUND, can cause untold troubles.
Ask me how I know? tenn...

[creeper]

Had my TCM replaced due to Camping world doing low voltage starts when it was in for an unrelated issue. Allison charged $1200 to replace it.

[chuckftboy]

Even though you have low mileage on your coach, the TCM is 13 years old and age takes a toll on electronics too. Turning your battery switch off probably has nothing to do with the failure as I am sure there has been many RV's with low voltage on their electronics while in storage. If this were a common problem someone would have posted it somewhere on one of the forums.

[bluebarry1964b]

Thanks for your input, guys. Very much appreciated!!

[Mike_Hohnstein]

It's always the ground.

[Busskipper]

bluebarry1964b wrote:
The computer on my Allison 2000 transmission (2003 Holiday Rambler Neptune) just blew. Mechanic said he only found one code on it that indicated "low voltage." He asked if I'd had battery problems. I hadn't. However, now that I think about it, I have the RV in storage right now, so I've been turning off the battery cut-off switches for both the house and engine batteries. I'm talking about the switches located in the battery compartment. I've been doing this as an anti-theft/ anti-fire precaution. I have been turning the switches back on every month when I take the RV out for a drive to exercise the transmission, brakes, etc. Then I turn the switches off again for another month. Could turning these switches on and off be the cause of the TCM frying? I'm concerned because it cost me $2,000 dollars to fix and if I don't know what caused the TCM to fry, then what's stopping it from happening again? Any ideas as to how to keep this from happening again? Crazy thing is the RV, although it is a 2003, only has 40,000 miles on it. Allison mechanic said he's seen the TCM's last 700,000 miles. I'd like to know why mine fried so prematurely.

Give this guy a call Had the same diagnosis a few years back and he saved me some real money on a missed Diagnosis.

BOL,

[CarlGeo]

Suggest you call John Kopalek at Transmission Instruments (866) 439-9779. He can give you expert opinion and advise.
Have heard about his legendary help.

All the Best
CarlGeo

[bluebarry1964b]

My regular mechanic couldn't even get the TCM to communicate with him, so I had the RV towed to an authorized Allison repair shop. The error code was stored, and they removed the TCM and "tested it on the bench." Prior to that, it sounds like they did check for loose/dirty connections, etc. My biggest worry is that because they couldn't come up with an answer as to what caused the TCM to fail, will I be replacing it again in the near future? There's nothing worse than fixing a problem, but not knowing how to prevent the problem from re-occurring.

[bdpreece]

With only a low voltage error I think I would be cleaning and re-seating all connectors and grounds before replacing anything. Especially if I drove it in and parked it for awhile then had a problem.

[dons2346]

The only one that can for sure tell you that the TCM "blew" is Allison. I wouldn't trust a mechanic to make that call

What symptoms do you have other than a low voltage code?

[Kayteg1]

Was the low voltage error pending, or stored?
Dealing with vehicle electronics is sometimes hard decision.
Logically you should have the computer fully scanned, troubleshooted and confirmed.
But such procedure can easy cost $300, while replacement computer board might be $100.
So to some degree taking a risk in dropping part without full scan can be a good bet.
Being mechanically inclined I become pretty good in car electronics as I could not stand technicians who would charge high hundreds or even thousands for computers, where $90 sensor was bad.
Get 2nd opinion if you can, or make sure the shop will take the computer back when they misdiagnose.

[noteven]

A certified Allison repair center should be able to test the TCM by itself for you.

[rgatijnet1]

Yours may not have been bad. It just may have been changed by a mechanic that used the "shotgun" approach to fix a problem. In other words, replace everything until it works. It is funny how a dirty connection can look just like a bad component. The difference is the time it takes to clean that connection or replacing a perfectly good component that will cost the customer several hundred dollars. The only way for you to tell is to keep the old parts and then reinstall that TCM after the vehicle is running properly to see if it is really bad.

[gbopp]

Dick A wrote:
When was the last time a "good" television tech fixed your television or stereo?

Yep, they're pretty much ancient history.