Towmotor UNKNOWN:
no throttle response

I have a 2003 towmotor that randomly has no throttle response and be in limp mode. I have had 3 different forklift mechanics work on it with no luck at finding the issue. I have changed the converter, fuel filter and vac solenoid. the pedal sensor test good. Initially it would start but no throttle response and in limp mode then shut off after a few seconds. Since converter change I get the same except it will continue to run in limp mode. Sometimes I can restart it and it run fine. Sometimes it will start and run fine for days. Other time it won't run for days.
  • Posted 17 Jul 2024 02:02
  • Discussion started by Martha_Waters
  • Florida, United States
Showing items 1 - 12 of 12 results.
I wish I were too , I also was a trainer for 24 years I taught diesel, gas and electric lifts
I taught that system when it first came out
Please let me know if I can be of any more help
Good luck
  • Posted 25 Jul 2024 12:49
  • Reply by John_Bradley
  • Texas, United States
Jb69
I will try to check that out. I believe I have the ecu information in one of the manuals. Not something I can do but I think one of my sons knows how. I wish you were close by, Its seems you have more knowledge than the ones I've had work on it.
  • Posted 25 Jul 2024 01:07
  • Reply by Martha_Waters
  • Florida, United States
If diaphragm has a hole in it or dirty it will cause your issue
Also note color of spring that is on diaphragm it is important to keep same color some have blue some red some yellow
  • Posted 24 Jul 2024 02:26
  • Modified 24 Jul 2024 02:32 by poster
  • Reply by John_Bradley
  • Texas, United States
Jb69
The only thing replaceable is the diaphragm
Note when you replace it there is an arrow or dash on it that faces the fuel in line fitting
If it isn't lined up it can cause issues
As far as ecu just checking inputs and outputs at connector but for that you need to know what each is supposed to be ie blue wire.5 volt etc
  • Posted 24 Jul 2024 02:23
  • Modified 24 Jul 2024 02:24 by poster
  • Reply by John_Bradley
  • Texas, United States
Jb69
I will give that a try today. Can the mixer be rebuilt? I have found that the mixer and throttle body are discontinued. Also is there a way to test the ecu without a computer program?
  • Posted 24 Jul 2024 01:22
  • Reply by Martha_Waters
  • Florida, United States
I would guess that the problem is with the mixer (carb) air fuel adjustment back when those came out sometimes even the factory guys had trouble getting the unit to work.
We had all the tools and program and we had some that took us a while and several parts to get right. One thing I can suggest that won't cost anything is to unplug all of the sensors and controller and put dielectric grease in them any component that the controller
Reads or operates. You could have a bad connection to a component and the grease will help keep moisture at bay
  • Posted 24 Jul 2024 00:58
  • Reply by John_Bradley
  • Texas, United States
Jb69
I put the new throttle sensor on Friday but that did not fix the problem. The only code it shows is 6 Engine Temp Sensor. I don't think that is the issue since previous owner put an inline temp sensor and external gauge on it and it has run fine for2 years. I did speak with Cat and the have one laptop with the program that will connect to it, for a heafty price of course.
  • Posted 23 Jul 2024 23:09
  • Reply by Martha_Waters
  • Florida, United States
Thank you I will try to get the code today. I also have the accelerator sensor (POT) coming today. Although it tested good previously I'm hoping that will fix it. I'm going to replace whatever sensor's that have been disconnected also. Yesterday I started it and it was still in limp mode so I turned it off and restarted and it ran fine. I moved it inside to work out of our Florida sunshine.
  • Posted 19 Jul 2024 00:51
  • Reply by Martha_Waters
  • Florida, United States
If the temp sensor is disconnected or faulty it can cause limp home situations
The limp home feature engages if engine overheats , low on engine oil or emissions
Components failure I would start at the engine temp sensor the limp home mode is to protect engine in case of overheating etc
  • Posted 17 Jul 2024 10:10
  • Reply by John_Bradley
  • Texas, United States
Jb69
Thank you for responding. Yes it is Towmotor Mitsubishi made by cat. No one has had a laptop to attach. It has a light that flashes a code but its related to a temp sensor being removed before I got it. My son tested the accelerator sensor and it test good. I'm guess that's what you refer to as rpm sensor? He tested when it was running correct and in limp mode both way's tested correct. I believe I can get a mixer but the throttle body is discontinued when I spoke with Cat this am. They do have the accelerator sensor but it is expensive so I'm trying to figure it out for sure before ordering more parts. I hope it's not the ECU, it's really expensive. This has been going on for months now and I have a large shipment coming the end of the week.
  • Posted 17 Jul 2024 04:36
  • Reply by Martha_Waters
  • Florida, United States
There is a method to retrieve codes it is called foot stomp you turn on key , wait 5 seconds
Hit accelerator all the way to floor 5 times
On fifth time hold to floor for 5 seconds then let up wait 5 seconds then hold to floor for 7 seconds then let up and count how many times light goes off and on it is hard to get timing right
May have to do it several times
  • Posted 17 Jul 2024 04:20
  • Reply by John_Bradley
  • Texas, United States
Jb69
I'm guessing it is either a cat or Mitsubishi
If so those were notorious for having that issue
There is a laptop program and cable needed if indeed that is one of those.if it is they had issues with mixer assembly and the rpm sensor to set the mixer you really need a laptop to watch the percentage as you adj
The adjustment screw is hidden behind a small
Plug it is there to discourage adj by untrained
Persons you can guess at it but really need the cable and program does it show a blinking light on the dash ?
  • Posted 17 Jul 2024 04:01
  • Reply by John_Bradley
  • Texas, United States
Jb69

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managing director of Liebherr USA, Liebherr USA
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Director, ICHCA Australia