Hey all, first time post. My wife an I have a Thomas School bus w a Cat C7 2005, an Allison 3100 I think. Today, this morning, we started the bus while in KY, drove from Il on our way to our place in TN. We were parked under a tree all night, but on start up, I had no throttle. Only code I saw one code from my ScanGauge was ID:231 FM:9 They think its a J1939 communications error. So I have no throttle, and no fast idle, but the bus starts and runs fine, everything else works fine. There no other codes. I crawled under the bus looking for anything out of place, loose wires etc. I reseated all the ECM plugs in the cab under my dash and all 4 of the TCM plugs under the bus from the Allison after someone suggested it on onother forum. I got towed in to a place, they said tomorrow , they will "try" to get me a new ECM and go from there. I dont think its the ECM but Im no mechanic, but neither do other folks tying to help me out on Schoolie Forums, although, they are also not mechanics. The shop Im parked in is also not a Cat shop, they work on any diesel. Any thoughts would be appreciated, is there anything I can do aside from having them swap the ECM?
231 FM 9 codes are attached but I have no idea here, is this a bread crumb ? That ID:231 FM:9 code appeared once the morning of the problem, then disappeared. Riight now the ECM has no stored codes.
I’d definitely have my reservations about letting them throw an ECM at it. Have they hooked Cat ET to it? There should be a parameter for throttle input to see if the ECM is seeing the throttle sensor.
RE: Have they hooked Cat ET to it? No they have not, they dont have Cat ET. I have it on my laptop but left it at home, DOH! Yeah. They have me over a barrel here. The have a generic looking ipad, they showed me my throttle, on a horizontal graph, it shows, in real time, the throttle position, while Im mashing it to the floor. So it appears to be working. The ECM sees the change in throttle position per their non cat tool.
Are they swapping with a used ECM or new? How will they program all the parameters without ET? Just curious.
I was thinking that too, unless they backup my ECM and drop that into the replacement ? Im not a mechanic, so no clue. Im assuming a Cat shop will need to do that ? Im wondering if I should pay another 600$ or more to get towed to a Cat shop instead. Thing is were on the road traveling so Im just trying to get fixed and keep going. Maybe I chose the wrong shop, but they had a Cat logo, Precision Diesel Repair.
Cat doesn’t recommend doing a copy config on an engine ECM because if your old ECM got corrupt, you could potentially corrupt the new one. I always download the status report and go through and manually program every parameter. Do as you like, but there’s no way I’d let them touch it. When they get it all jacked up you’ll be paying Cat to sort it out and get it right.
Based on my experience if it’s starting and running it’s rarely the ECM. I’d be lookin at wiring or some other input making the ECM kill the throttle. ABS issue? Ghost signal of some sort from vehicle speed sensor? Something in the communication from trans to engine? If their first reaction was an ECM I believe I would drag it to a cat shop or at least a shop with ET and somebody than can use it.
Makes sense. Im not sure what to do here then. Tomorrow we'll see I guess, they said today they will go the eCM route, no guarentees it will fix it. Tomorrow Ill see based on what they say, if I get it towed to a Can shop. I found this on 20 miles away, I dont know their reputation, but they seem like a big cat dealer, Ill call em tomorrow. https://boydcat.com/service/
Livin’ the van life?
LOL, no , the bus life : ) OK, just spoke with Boyd Cat, Im having it towed there tomorrow, I agree with everything you all said. Im not going to let them jack this up then have Cat fix it. Some time ago, last yr, I saw a ABS light, it went away by itself. Ill mention a possible ABS as a thing to test.
Just playing around with my ScanGauge, I found the TPS fields. I verified as Im mashing the pedal down, were seeing position changes.
The error code could be a glitch. Perhaps check the transfer pump fuel pressure. Maybe the fuel pressure regulator on the back of the head is stuck open and it doesn’t have enough fuel to do anything but idle.
Where are you plugging in your scan tool? What does the connector look like? I suspect you may be looking at what the Allison ECM is seeing. As mentioned above, if the engine runs I would first suspect a sensor/wiring issue on the bus side. Engine serial number required for more info.
What branch of Boyd are you having towed to? I have a couple of contacts there.
Can you see if there is a bus door throttle interlock switch showing with the ScanGauge?
Update from yesterday, problem is solved. While waiting on Boyd to stop by for a remote support, I again went thru the bus, this time focusing on doors and windoes which still had interlock switches. It was indeed a door interlock issue. While driving the very bumpy IN roads, the handycapped door interlock switch shook loose, thus showing the door as open thus disabling the throttle. Soon as a I found that, throttle worked. The diesel mechs said they would never have found that. Of course, in 2005 when this bus was built by Thomas, they failed to build in any door interlock warning lights for the driver. Thank you ALL for assisting me with this issue, I really appreciate it!
Well that was a lot cheaper than those mechanics
I never would have thought about door interlocks.
Shows what we know about passenger busses Coaldust
Good information to know, if my wife ever kicks me out of the trailer and I have to live in a skoolie.