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BAC Forum    General Boards    General Discussion  ›  CAT 2008 C9 ENGINE PROBLEMS Moderators: LarryNCarolynShirk

CAT 2008 C9 ENGINE PROBLEMS  This thread currently has 2,774 views. Print
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March 31, 2011, 5:51pm Report to Moderator
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Location: Corrales, NM
3/28/2011 2008 CAT C9, 425hp)  PROBLEMS/MOTORHOME, aprox  miles 9832!
On AZ Hwy 260, 21 Miles from Heber, AZ engine suddenly went from 6/5 transmission status to 2nd gear.
Power immediately lost.  No check engine light appeared.  In checking the diagonostics provided by my consule, there were NO diagonostics/faults recorded.  Transmission would NOT shift out of 2nd gear.  

I turned off the ignition, and when I turned it back on a check engne light registered on console.  I turned off the engine again, waited a short time and tried starting it again.  This resulted in the console showing a
6/1 status on the transmission control panel.  However when I tried to drive, (to get to a safer place) the engine/transmission would not go higher than 6/1.   After trying to figure out how to check codes on the Allison Transmission 3000MH I saw what appeared to be a EL code appear, I later learned that this was probably not an EL but an E1.  All other attempts at receiving any codes only seemed to produce dashes (--) which told me nothing!!  Obvisosly I could NOT discern what the problem was.  

After 5 hours of waiting for a tow some 3 hours away, the engine and/or transmission had cooled down such that when the tow technicial from Coach Net arrived and we checked out many things, the engine started right up (again with NO codes detected/recorded).  The tow truck followed me some 21 miles down to Heber, AZ with NO problems with engine or transmission.  

3/29/2011 (next day)

Drove to Gallup, NM without any incidences.


Left Gallup, NM, had driven less than 5 miles and had just pulled onto I-40 EB, when suddenly the engine lost all power,  was still runnng BUT registered 0 RPM's.  I pulled off the road, ran the console diagnostics again and again NO faults were recorded!!  I pressed the accelerator again and suddenly RPM's were showing and registered on RPM guage.  I proceeded traveling and finally arrived home (Corrales, NM) with no additional problems.  I checked the console for any recorded faults, again NONE.


I know there is an up date to the check engine light which I intend to have done now that I am back in ALB., NM, but my understanding of it is that all it does is extend the "allowed" range BEFORE the light comes on and DERATES the engine.  

Hey those of you who have this C7/C9 400/425 hp engine and have had this update please let me know your experiences and "words" of "wisdom".  

Gerald, any thoughts????

2008 Contessa (425 hp Cat) 38'
PT Cruiser/SMI braking
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Richard And Babs Ames
March 31, 2011, 7:40pm Report to Moderator

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Have you tried turning off your exhaust brake? Sounds like some kind of ground prorblem.

1997 Beaver Patriot
3126B  CAT  
South Central FL
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March 31, 2011, 7:51pm Report to Moderator
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I don't use the engine brake except when needed.........I don't drive with it on like some do.
That would have nothing to do with the problems describe in my opinion!

2008 Contessa (425 hp Cat) 38'
PT Cruiser/SMI braking
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Joel Ashley
March 31, 2011, 8:38pm Report to Moderator

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Sounds like something that's liable to happen again, Leah.  If there was something haywire with the engine, it likely wouldn't show up in the tranny codes;  but then you didn't get a Check Engine lamp either.  It is odd that your RPM guage showed 0 with the engine running;  that may be tell-tale to a good tech, and could be indicative of a computer glitch that's falsely sending the engine into a defensive mode.

There are 2 Allison service outfits in NW Albuquerque, but perhaps a CAT tech should check the engine codes for faults - your local CAT facility is probably Wagner's?  Any discovered problem may be covered by your CAT and Allison warranties.


Joel and Lee Ashley
36 ft 2006 Monterey
C9 400HP Cat
Beaver Believers
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Gerald Farris
March 31, 2011, 10:33pm Report to Moderator

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I can not give you any answers to your problem from the description, except that it sounds more like an engine problem than a transmission problem. However it does not sound reasonable that the engine would have derated without setting any diagnostic codes.

One thing about taking the coach in for service is that if there are no diagnostic codes and the engine is running normally at the time, they may not be able to determine the problem, and say "we can't fix it if it aint broke". Then expect you to pay for the check out labor time since no warrantable engine problem was found.


2000 Marquis, C12
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Ken Buck
March 31, 2011, 11:36pm Report to Moderator
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You might want to note if it happened to be raining at the time of the problems, (wet connectors) or if things like headlights were on, (low voltage) etc. Intermittant problems are hard to diagnose and expensive. You want to tell them in writing (by way of a note) all the "conditions" when the problems happened. Sometimes a little thing that to you or I doesn't seem important will trip in the mechanics mind and lead him/her down the better path to solving the problem.
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Bill Sprague
April 2, 2011, 2:32pm Report to Moderator
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I don't have your engine but I had a bad engine day a few years ago.  The engine was not running well and a warning light was flashing intermittently.  I've written about it before so I won't provide all the details.  But, I got the coach to a Cummins shop.  The flashing light and various codes were confusing them  Finally, after 6 hours of troubleshooting, and experienced mechanic changed the almost new fuel filters because he thought it might be a good idea.  The problems went away and have not returned.  Apparently I had some bad fuel and the engine computer was going nuts because the fuel pressure and flow fluctuated.

Bill Sprague
Region 1 VP
2004 Monterey
ISC 350 Cummins
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April 2, 2011, 5:42pm Report to Moderator
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THANKS BILL for your thoughts about the fuel filters, I'll keep that in mind.  You never know when you can get bad fuel or a "bad" new filter!

2008 Contessa (425 hp Cat) 38'
PT Cruiser/SMI braking
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