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A diagnostic problem -- where would you start???

Yahoo Message Number: 116063
OK folks -- here's a problem to solve. If you have had any of the same experiences, I would love to hear from you. We were on our way from Reno, NV to Bozeman, MT. yesterday afternoon when our 2003 CC Magna crapped out in the middle of the Nevada desert. I managed to nurse it home, stopping frequently to let it rest, and finally made it, to our great relief. To those of you who would like to hazard a guess as to what led to the problem, here are the symptoms. As I said, I would greatly appreciate any advice.

Thanks in advance,
David Jarrett
2003 CC Magna #6240

center
center
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CONDITIONS:

1)Transmission goes into limp mode after a few minutes of driving. After stopping, turning off ignition and waiting a few minutes, resumes normal function for a few minutes before going into mode again. Once in this mode, it will not shift, but will stay in gear selected when restarted, and will respond to throttle control.
2)Transmission keypad goes completely black, with no codes showing, but "check transmission" light is on. When prompted for codes:
A)With engine running, keypad window counts down from 7 to 1 and then announces oL OK.
B)With engine off, keypad window shows oL 5.0 (Engine speed too low).
3)On Silverleaf display, most functions (including RPMs, temps, battery voltage @13.8V, HP %, etc.) displayed accurately with the following exceptions:
A)Speed shows 0.
B)Cruise control setting shows 0 even though cruise control is set and working.
C)Instant MPG shows 0.
4)Dash gauges:
A)Voltmeter shows 13.5V+ except when ignition turned off, when it drops to 0 (this it has never done before).
B)Speedometer and odometer function erratically at first and then stop working altogether.
C)Jake brake light comes on along with the above, even though it is not activated.

Re: A diagnostic problem -- where would you start???

Reply #1 –
Yahoo Message Number: 116064
Communication bus for the transmission failed. My guess the connection between the transmission and the controller came loose.

Mark
07 Inspire 51985

Re: A diagnostic problem -- where would you start???

Reply #2 –
Yahoo Message Number: 116065
Try this. With engine off and not connected to shore power, disconnect the chassis batteries, wait 30 seconds, reconnect. Determine if the problem is resolved.

Lee Zaborowski

Re: A diagnostic problem -- where would you start???

Reply #3 –
Yahoo Message Number: 116069
With my Allure the communication cable between the engine and transmission was to close to the exhaust manifold and fried the wiring. TWI 98 Allure 30255

Re: A diagnostic problem -- where would you start???

Reply #4 –
Yahoo Message Number: 116070
Hi folks. Thanks for your responses thus far. Rebooting the system by pulling battery cables, waiting an hour, and then reconnecting them did nothing to solve the problem. I did, however, pull a new code from the transmission indicating, again, low voltage to the ECU. Now my problem is to FIND the ECU so that I can try to trace the wiring to it. Thanks, Thomas, for your post. I shall look around the engine bay for it, now that I've pulled up images from the Internet and know what it looks like. If any of you have had the same problem and have found other place where the ECU is mounted on your coach, please let me know. Thanks!

Re: A diagnostic problem -- where would you start???

Reply #5 –
Yahoo Message Number: 116071
There should be 2 fuses coming off the chassis batteries in inline fuse holders, one for the engine ECU and one for the trans. Check them for corrosion or bad connections. These 2 fuse holders tend to be problematic.

Mikee

Re: A diagnostic problem -- where would you start???

Reply #6 –
Yahoo Message Number: 116072
Had similar problem with transmission not communicating with engine. Was told wiring bundle to close to muffler and exhaust. Had to repair bundle (I think was labelled 1939 bundle) and put an aluminum heat shield between bundle and exhaust on our 2007 inspire.
Frank



Re: A diagnostic problem -- where would you start???

Reply #7 –
Yahoo Message Number: 116073
Well I found the VIM & ECU -- both in the steering bay as far back as CC could have put them, behind a maze of ziptied wires. I'm assuming the power from the batteries has to go to the VIM first and then to the ECU, but haven't found the answer to that yet. Both the positive & negative leads to the VIM look fine and the connectors are bright and clean. There is nothing in the battery compartment to indicate any direct connection to either the VIM or the ECU -- no inline fuses that I can see -- just huge wire looms full of different wires that I hesitate to take apart, and I have serious doubts that I will be able to trace a single hot lead all the way from the battery bay to the steering bay, so I think I'm at a dead end. I'll probably end up taking it to Allison and pay megabucks to have them diagnose & fix the problem -- could be the ECU itself, I guess, although the fault just seems to be inadequate voltage to it. If anyone else wants to chime in on this, please feel free. Thanks!

David Jarrett
2003 CC Magna Resort #6240

Re: A diagnostic problem -- where would you start???

Reply #8 –
Yahoo Message Number: 116077
I am now getting what I think is the correct code from the Allison keypad. It's the 35 00 power interruption code, indicating loss of power to the VIM & ECU. Since the no shift/limp mode problem kept repeating itself all day from the middle of the desert back to Reno, through many ignition on-off cycles, I don't think it was just a momentary thing and will certainly recur the next time I take the rig on the road. Now the problem becomes how to trace the wiring through the maze of wires in the steering bay with both units buried behind everything else.

DRJ

Re: A diagnostic problem -- where would you start???

Reply #9 –
Yahoo Message Number: 116079


I'm going with Mark. Had the same happen to me and it was the electrical connector between the Engine and Transmission. It came part way apart so that when stopped things seemed OK but as soon as speed was up a little the wind blew it apart far enough to disconnect, and back to limp mode. Easy fix, snap the connector back together.

J Hodges
2007 Inspire

"Life Is Short. Live It To The Fullest. It Has An Expiration Date!
YOU CANT GO BACK AND START A NEW BEGINNING,
BUT YOU CAN BEGIN TODAY AND CREATE A DIFFERENT ENDING!
"Let us do and let our deeds cast long shadows ... let us remake the soul of our people, let us throw ourselves into the future. I ask of life only one thing, use me."
-Attributed to Joseph Guibord

Re: A diagnostic problem -- where would you start???

Reply #10 –
Yahoo Message Number: 116080
Thanks, Jim. I'll try to get under the coach and look for the connector. There isn't much clearance, even with the airbags all the way up, but it sure would be nice if that's all there was to the problem.

DRJ

Re: A diagnostic problem -- where would you start???

Reply #11 –
Yahoo Message Number: 116082
Where is the connector you refer to Jim (between engine and transmission) located? I have heard of folks who had a problematic rubber encased plug near the top of transmission have issues with water intrusion, bad contacts. Is that the same connector?

Greg
06 Magna
2006 Magna Rembrandt C13
2016 Jeep GC toad

Re: A diagnostic problem -- where would you start???

Reply #12 –
Yahoo Message Number: 116083
Get some smaller wood blocks and drive up on some 6x6 ties. I use them to service my coach and that way if it drops air you won't get crushed. The 6x6 make a nice roomy area under the coach and it's safe!

Re: A diagnostic problem -- where would you start???

Reply #13 –
Yahoo Message Number: 116084
Greg,

My connector, which came loose, is in the control bay under the drivers seat.

Mark

Re: A diagnostic problem -- where would you start???

Reply #15 –
Yahoo Message Number: 116086
I wasn't smart enough to do that -- I'm old enough to know better too! It was kind of scary under a 38,000 lb. coach & I didn't like the feeling, but I got away with it and didn't find any loose connectors. I did find one wire towards the front of the transmission near the bottom that was only connected to the transmission by a tight enough but very dirty and not at sll watertight connector that I cleaned & tightened before scrambling out of there. I would caution everyone NOT to follow my example and heed Marvin's advice -- put something under the frame of the coach to prevent it from settling on you if the airbags suddenly decide to deflate. I'll never go under it again without doing that! I did check the hot wire to the VIM, and it's definitely getting current even with the ignition off. I couldn't follow the wiring from the VIM to the ECU, but I can't see any reason it should be bad. I cleared the 35 00 code & will road test the rig tomorrow to see if the problem recurs. Thanks to all of your for your advice and encouragement!

DRJ
2003 CC Magna #6240

Re: A diagnostic problem -- where would you start???

Reply #16 –
Yahoo Message Number: 116087
Going under a 38,000 Lb. RV without jack stand protection leaves me speechless, then brag and lecture everyone who reads your message, has me a bit confused or your just a big shot who got away with it.
CC5851

Re: A diagnostic problem -- where would you start???

Reply #17 –
Yahoo Message Number: 116088
Boaterallan -- Rather than being speechless, you seem to have a lot to say, and all of it negative. Where in my last message do you see anything that would be construed as bragging??? The main thrust of it was NOT to follow my example and go under a large vehicle without using supplemental supports -- more of a "mea culpa" than anything else. I freely admit it was a stupid thing to do -- done without thinking things through and BEFORE reading the constructive comments urging me to use jack stands. Your comment was not only non-constructive, it was insulting and reminiscent of someone who only wants to hear himself talk. And NO -- I am NOT a big shot!

DRJ

Re: A diagnostic problem -- where would you start???

Reply #18 –
Yahoo Message Number: 116089
OP - Glad you got out OK, and i've done some things that in hindsight were not all that smart too:)! And yes to all of you who posted the caution of following safety rules carefully.

Back to the problem, I've been following the thread closely. We've had a fantom problem since we bought the coach, coming up on 8-9 years ago now. It's not consistent, but say climbing a hill in 4th gear, if I hit a road defect (Not difficult to not his a road defect no a days:!)! - the impact will result in the transmission shifting down a gear, to 3r in this example, then usually right back up into the gear it was in. This can happen on flat ground too, while under acceleration. And, if just cruising along at highway speed in 6th, it will also sometimes do this and jump down into 5th then to 6th again too.

On previous threads where I've posted help for this, many have suggested some of the same diagnostics that you have been going thru. And I've tried them all, but never found it. I talked with an Allison Tech about the problem, and he said he'd seen some harness plugs with bad pin connections. With just one pin loose enough that impact shake of the drive wheels will cause the pin connection to momentarily disconnect, and cause strange symptoms, then reconnect and things will rest. His recommendation was to start at the rear, and replace all of the harness plugs. Which due to the nature of the effort to involved can be expensive. I've unplugged them all, or at least the ones that I can find, sprayed them with electric cleaner, dried, then reconnected and made sure they were properly connected and watertight. I've also traced as many of the grounds that I could find, and cleaned them too.

Did not seem tot help, and as it happens intermittently, I've elected to monitor the situation until, or if, it becomes worse. Which it so far has not yet done... (Knocking on head now:)!).

Though I suspect coaches with the larger Allison 4000 transmission, and say CAT vs Cummins, could have different harness and ECU's involved then my ISL and Allison 3000 - the fundamentals of debugging such problems are probably the same.

Looking forward to you find hopefully a not too expensive root cause, and correction. Best of luck to you,
Smitty
04 Allure 31017
04 Allure Sold to a nice new owner! Now enjoying a 07 Magna Rembrandt 45' ISX600 #6775
"We're ONDROAD for THEJRNY!" (Toad and Coach license plates, say Hi if you see us!)

Re: A diagnostic problem -- where would you start???

Reply #19 –
Yahoo Message Number: 116090


Mine was under the coach and below and between the engine and Trans. Not knowing what the problem was, I nursed the rig into a Cat. dealer in Yakima, WA. and the Tech., after some diagnosis, rolled under the coach, snapped the connector back together, (he said the connector was only hooked on one side, probably at the factory) and all was well. The best $80 I ever spent.

Jim Hodges

ex-owner 2007 Inspire
"Life Is Short. Live It To The Fullest. It Has An Expiration Date!
YOU CANT GO BACK AND START A NEW BEGINNING,
BUT YOU CAN BEGIN TODAY AND CREATE A DIFFERENT ENDING!
"Let us do and let our deeds cast long shadows ... let us remake the soul of our people, let us throw ourselves into the future. I ask of life only one thing, use me."
-Attributed to Joseph Guibord

Re: A diagnostic problem -- where would you start???

Reply #20 –
Yahoo Message Number: 116091
Thank you, Smitty. I appreciate helpful posts like yours. :-)

DRJ
2003 CC Magna #6240

Re: A diagnostic problem -- where would you start???

Reply #21 –
Yahoo Message Number: 116092
Well today, just to try to cover all bases, I pulled out the shifter panel and checked for loose wires -- found none. I checked the ignition solenoid in the steering bay with a multimeter, and found adequate voltage both at the "hot" side from the batteries and through when I turned the ignition key on. Then, after a fight with a mass of bundled wires, I finally got the eight 5/16" bolts out of the VIM cover, and looked inside. I pulled the 10A fuse and it looked fine, but replaced it with a new one anyway -- you never can tell with automotive fuses. The eight relays were just sitting there -- no way for me to test them, so I just pushed in on them to make sure they were tight, and replaced the cover. I don't know why CC mounts these parts in such inaccessable places -- do they think they're never going to fail? There are plenty of other spots in the steering bay that would have taken no effort to get to -- just a little extra wire expense to CC. I have yet to find any fuses between the batteries and the VIM/ECU that some have you have referred to. I'll keep looking, but I'm not sure this coach has any. Again, thank you all for your input. I hope some of you find the journey interesting.

DRJ
2003 CC Magna Resort #6240

Re: A diagnostic problem -- where would you start???

Reply #22 –
Yahoo Message Number: 116093
I'm glad for you that it was such an easy fix. I hope I can get mine resolved.

Safe travels,

DRJ

Re: A diagnostic problem -- where would you start???

Reply #23 –
Yahoo Message Number: 116094
What did you see in my post that would constitute bragging? It was more of a "mea culpa" if anything, admitting it was a stupid thing to do, and urging others NOT to follow my example. And NO -- I am not a big shot!

Re: A diagnostic problem -- where would you start???

Reply #24 –
Yahoo Message Number: 116095
Your description is exactly how I read your post. Your point was not to do it ever, and you're very grateful that you didn't have anything bad happen to you.

Mary
06 Inspire 51784