Trouble shooting the TCU and ECM

[Mike in Va]

My MH is in the shop with a "Trans Light" and "low water" lights on. This first happen in maine after sitting for 4 days. When we started home the lights came on and when a computer was attached to it no codes showed up but the lights went off. Now their on again. I dropped the MH off at the shop and both lights were on at the time. They called today and told me the lights went out and they drove it and can't get the lights to come on now. When the lights are on my temp in the trans climbs very high.  Their were able to get something that said communication error. They said they are aren't sure if its the TRM or the ECM or even the wiring harness that connects the two. I'm going up tomorrow to drive the MH and hope the  light comes on and to talk to the shop foreman and hopefully find some answers. Can the ECM or the TRM be tested individually without taking them off to check if they are ok? Thanks       

[bobdinsmore]

A couple of times out of the clear blue my Check Engine light came on in the morning with a collection of codes that didn't make sense. But in my case they went away after driving quite a few miles. It struck me the codes were the result of slight oxidation aggravated by early-morning humidity that dried up when the engine heated. This may be what's going on with you. Just a loose thought...    🙂

[Mike in Va]

Bob thanks for the input. I was able to drive the mh 50 miles to the garage at 55 mph. If I down shifted or went up a small hill the temps would start up. Soon as the rpm's were reduced the temps would go down.  The trans light and low water stayed on the entire time driving and was on when I left the mh at the garage. The garage said the trans seems to be going into limb mode just not sure why. One thing I forgot to mention is at the same time my oil pressure gauge on the dash would jerk all the way to the right side for a second and return back to normal. This happen several times also.  Trying to get this problem fixed because we have two trips planned in the next month.   

[USMC E-5]

Mike ,Had similiar problem had a loose ground in rear big boy compartment ,green plastic block upper left cornerwith 14/16 gauge white wires,all were not tight?? white  ground was one was the ECM which caused warning on dash and shutdown. Hope it works out for you.

[PeterSchweizer]

What / where is the rear big boy  compartment ?

BTW a 2008 42 ft coach is no where close to a 2001 in almost every system n layout

Edited October 6, 2021 by PeterSchweizer

[Mike in Va]

Thanks to everyone for the help. I THINK I may have found my problem. When I picked my mh up the technician suggested that I fix a couple of things and see how that works out. On my first post I forgot to post that my abs light had been on for awhile also.  I drove the mh home with the abs and low coolant lights on. I installed a new /old stock ABS computer and had the batteries checked. Batteries were 10 mts old but one was tested and showed lower voltage then the second one so the store decided to turn them in for two new ones. After installing the batteries and computer I drove the mh and within 5 miles the abs and the low coolant lights went out.  I have driven the mh 2 times a day and so far NO lights have returned. I'm holding my breath now and hoping the problem is solved. Taking a 200 mile trip on Monday for 4 days so I will see.