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Old 08-08-2018, 09:25 AM   #1
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Locating Engine and Transmission ECU's and VIM

2006 Holiday Rambler Imperial 42 w/ISL 400. Can anyone tell me where to look for the ECU's for the engine, transmission and Bendix ABS units before I start tearing into my coach? I have a gremlin that is affecting all three drive train components and the schematics I have for the 06 Monaco products fail to cover the drive train and it's communication wiring.

I am truly desperate and here's why. We barely made it home yesterday afternoon from a trip across the mountains, with the coach finally dying in an intersection just a block from my house. After disconnection the car and apologizing to several people unable to get by, I was eventually able to get restarted and limp my way up the hill and into my driveway.

As we were coming over Stevens Pass, the ATC switch was illuminating on and off and soon after I got a solid ABS fail light on the dashboard. We pulled off, shut down and looked things over, then restarted the engine. No lights, so we continued on.

Jump 50 miles or so. Bumps in the road were starting to make the Check Engine light flash, often but not always, concurrent with the ABS light. It became more pronounced as we traveled until one good bump not only flashed the warning lights, the transmission downshifted to a lower gear, than upshift again normally when the lights went out. At one point on I-5 north of Everett we pulled off because we lost power. I soon realized we had been bumped into neutral. Then came completely dying just before reaching the house.

When we did get home, I noted the dash display was indicating a transmission communications error. I pulled trouble code 3500 off the first register in the tranny with no other codes captured. 3500 is “Power Interruption, Real Time Write Interruption” with recommendations to check the TCM/ECU and VIM connectors, power and ground connections, etc. I found nothing but got a lot of dirt in my face crawling around under the coach.

What is really puzzling me is along with the ABS light, it was the Check Engine light coming on, not the Check Trans light. Never once did the Check Trans light illuminate, but the trany still threw that code. Go figure.

I am afraid to take the coach to a repair center until I give it my best shot. I can just imagine the bill for troubleshooting this one.

Stuart Thornton
2006 Imperial 42PBQ
2012 Jeep Sahara
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Old 08-08-2018, 09:58 AM   #2
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I feel your pain Stuart. Wish I could help but really have no idea other than I would sure check that tranny wire that connects to the batteries. I know from experience that can cause momentary problems that kill the engine/tranny. Also look for a butt splice connector about two feet back on the tranny wire and replace that. This is really just a wild ass guess but it was a problem on my rig.

No fun having the rig dying on I5. Glad you made it home.

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Old 08-08-2018, 10:01 AM   #3
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I cannot help you with the exact location of your control modules. But, did the engine run rough with little power? If so, the first thing I would check is your fuel filters. A plugged filter can almost cause you to think you blew an engine. The abs light on mine will come on if speed and rpm are under a certain number. If the engine is lugging the transmission will shift gears.
Might not be your problem but worth ruling out. You description makes it seem that the problem continued to worsen. That would go along with the filter restriction gettin worse. I got a tank of bad fuel in New Mexico last year, almost didn’t make it to a pull off.
You really need to see if you can read your engine fault codes.
Happy Camping, Safe travels and may our paths cross someday!

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Old 08-08-2018, 10:08 AM   #4
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Follow the wires, They will lead You to the ECM.

Either before of after you find the ECM,

I'd get someone to sit in the drivers seat Key on- engine off (Watching the dash lights) and yourself poking, proding the wires and connectors to find the loose connection that has to be somewhere.

check ALL grounds.
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Old 08-08-2018, 10:39 AM   #5
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funcky behavior

I think before you get into complex trouble shooting --- you try some simple fixes. the bumps affecting things the way you describe sounds like a loose connection. Could be a dirty connection right at the battery. if it seemed like when you experienced bumps if it happened when the rear wheels bumped or the front. If front look at connections that feed the ignition sw. the big run panel up front I think has connections dozens of them but the primary wires perhaps are what you're interested in. These can cause multiple systems to act up as you describe, main supply's can cause these problems. In my motor home there is a major conductor to the front run panel that feeds the ignition sw. from the ignition sw power goes through the transmission selector and other interlocking devices before a signal gets to the engine. So it doesn't have to be expensive computer modules causing your problem. Just a loose plug or corroded connection-- here's your chance to save money.

So a person like yourself who can carefully look at, wiggle and clean or tighten any suspected primary sources of power to your motorhome hopefully will produce a fix for your problem.

the engine computer on most Cummins engines is on the passenger side of engine just above where the pant attaches to the block near the flywheel end of engine. Hopefully someone else can advise your where others control modules are. Hopefully the simpler fix will yield results. My experience as a repair tech, loose, corroded connections are what to look for first.
Hope this helps
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Old 08-08-2018, 11:10 AM   #6
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Stuart, the trans. module is just below the shifter key pad. Buy a can of contact spray cleaner (CRC Home Depot) and start spraying all contacts. Especially the ones going to the trans. Its the big round metal ring with grooves around it. You have a poor connection some where.
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Old 08-08-2018, 01:24 PM   #7
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I would check all the connectors and see if one has come apart. I had one come apart
on my rig and lost gauges and tach and then it would reconnect. The trouble I had was
finding the connector. The vim on my rig is below the shift selector
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Old 08-08-2018, 01:32 PM   #8
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On our entry level coach the ABS box and TCM are in the front run bay under the drivers seat, The ECU is in the right rear storage compartment behind the rear wheels. As others have said I would start with checking for loose connections.

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Old 08-08-2018, 01:37 PM   #9
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Cummins , ECM is usually on the motor , intake manifold side , away from the exhaust heat.

With your multiple; ECM; , issues , I'd be after the main connection between the engine and transmission , harness and the the connection at the frame rail to the chassis wiring.
Here are pictures , of what your Allison controller and VIM will probably look like. 06 should still be WTEC III
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Old 08-08-2018, 02:32 PM   #10
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Before you tear it all up, try this.
I had several intermittent errors and the cruise worked maybe 1/2 the time due to a transmission code saying no communication.

Go to home depot and get a bottle of NoAlOx. It's in the electrical section.
It's a conductive grease for aluminum connections that oxidize.
Take every pigtail apart and put this stuff in the female holes. Clean the excess and re-connect.

I did this and ALL my intermittent issues went away!!
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Old 08-08-2018, 05:52 PM   #11
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I can't believe it. Just typed a lengthy response and hit "Submit Reply'. It totally disappeared and I have to type it up again.

Thanks for all the feedback and suggestions.

I was replying that I found the engine ECM on the engine, Trans ECU and VIM in the forward cargo bay ceiling, and had ordered a scanner to read the engine codes, if any.

I went out to the coach to turn it around because it is really hot outside and I wanted the back in the shade. I hit the key and nothing. I now have a hard failure.

Check Engine light - on
Check Trans light - on
ATC illuminated switch - on
Allison push button keypad - dead
Trans Temp Gauge - swinging H - L - H in 5 second cycles
Dash display showing "Transmission Comm Err"

I can turn around now but tomorrow I have something firm I can work with when I get home.
Stuart Thornton
2006 Imperial 42PBQ
2012 Jeep Sahara
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Old 08-08-2018, 07:25 PM   #12
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Page 261 of your owners manual:
The System Control Center (located behind the overhead access panel between the rails of the bay
compartment) consists of the following components:
• Engine Vehicle Interface Relays &
Transmission Electronic Control
Unit (ECU): Electronically monitors
and controls engine and transmission
functions and operating conditions.
• ABS/ATC Control Module: The ABS/
ATC controller monitors road speed of
each wheel, braking conditions and ABS
• Air Leveling Control Module and
Sensor: The Air Leveling Control
Module operates air solenoids that are
mounted in manifolds located above
each axle to control Raise, Lower and
Travel functions. The Air Level Sensor
is located on the HWH Air Leveling
Control Module.

This is all covered in your owners manual electrical section 9.
Download your owners manual here:

I agree with some of the others in that the common thread here is a ground or the engine batteries.
I would start by cleaning the engine start battery terminals and the master cutoff switch terminals.
Hope this helps.

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Old 08-09-2018, 11:25 AM   #13
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Call REV and ask them for your 'datacard' - (they emailed it to me within 30 minutes of calling) it has EVERTHING related to your equipment,including serial numbers of all your appliances,etc... then when you get that register for free at cummins quickserve to get your particular engines data...
good luck !
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Old 08-09-2018, 01:50 PM   #14
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The Cummins ecm is on the engine. The Allison and any others may be in one of your bays under the ceiling.

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cat, engine, transmission

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