Toyota 5FBC25:
C0 code truck not traveling in forward or reverse material handling system is functioning

Hello,

I have been trying to troubleshoot this issue for over a week without success. I have repaired a few forklifts in the past but this is the first Toyota for me.

This lift is new to me. Since I received it, it's Throwing an error code C0 that comes on when the key is turned on.

I have gone through the troubleshooting guide in manual as best as I can follow but the manual very hard to follow and I think it leaves some information out.

I have tested the drive unit transistors and the contactor coils. One of the contacts (MG) is chewed up but it's not sticking on. I monitored the coil voltage for that contactor during startup and it was never energized.

At startup the only contactor pulls in and it's not in the drive unit its the MP contactor on the material handling panel.

I've inspected all of the cabling going to/from the drive unit.

The battery appears to be good and is fully charged.

I got what appeared to be incorrect reading when ohm ing the DAD and flywheel diodes and the RAD but I will check them again.

I do not have access to the SST to test the boards.

I performed the continuity check on 2-38 from the manual I got the following:
P2->N1 = 5.8K (Should be 10 to 25 ohm)
N1->P2 = 3.0K (Should be O.L)
P12->N1 = 0
N1 -> P12 = O.L.
I could not see the test conditions for this test anywhere so I had not disconnected anything prior to the continuity test.

Can someone please help me pull this together so that I can understand the next steps?

Thanks for your help.
  • Posted 13 Dec 2020 02:34
  • Modified 13 Dec 2020 02:56 by poster
  • Discussion started by IMECH
  • Texas, United States
Thanks for your time
Showing items 1 - 14 of 14 results.
I can't speak for Toyota in US as I have no experience with them there but in Europe they do things differently.
  • Posted 25 Jan 2021 21:20
  • Reply by Roibeard
  • Dublin, Ireland
I have finally identified the issue. Its the DC-SD? board. The board that is part of the drive panel but over to the side. For some reason an identical board (same part number) was used for the material handling chopper so I was able to swap them and my C0 became an E0. so now instead of being able to lift not drive I can drive not lift. I ordered a used board and should have it tomorrow. Thanks for your help.

P.S. I now have many extra parts that I bought used and did not end up needing for this lift nearly an entire drive panel with boards, contactors, diodes, etc. I have several resistor assemblies and more. Does anyone have any suggestions on where I might sell them?
  • Posted 25 Jan 2021 20:35
  • Reply by IMECH
  • Texas, United States
Thanks for your time
hi , changes again the thyristors , i am sure it is the problem
  • Posted 25 Jan 2021 20:08
  • Reply by tr_doctor
  • Netherlands
Regards
Umm. So you get a permission from toyota to do such a change over ??? Here in the US we have rules to follow and cannot change whatever we want to something else. It's called liability! Not to **** but this is not a option for us in the states!
  • Posted 25 Jan 2021 13:22
  • Reply by ron_k
  • North Dakota, United States
Ron kornkven
When the cost of replacement components stacks up on Toyota drive systems I replace the complete system with a Curtis control unit, cheaper and less fault finding in the future.


Having said that, CO is mostly commonly caused by damaged power transistors (typically caused by using the forklift to push something). As already mentioned change all the drive power transistors as they are matched otherwise you will get thermal runaway and damage the transistors again AND ALWAYS change the flywheel diodes, they protect the transistors from back emf caused when the transistors switch the inductive load, ie the motor. On the FBMF models I have found diodes also short circuited on the drive control boards.

If the main CPU board is damaged along with the power transistors I call a halt and retrofit with a Curtis control unit. I use the MG, regen contactor, to drive the hydraulic motor and the pump contactor as a line contactor for the Curtis controller. This saves buying a contact assembly for the line contactor and saves having to find space to accommodate it plus reduces the amount of wiring required to connect the Curtis unit.
On one occasion I found the line contactor overheated every 6 months which was due to a poor battery so to save on replacing the battery I added a cooling fan next to the line contactor.
  • Posted 25 Jan 2021 07:44
  • Modified 25 Jan 2021 08:18 by poster
  • Reply by Roibeard
  • Dublin, Ireland
Hello , if you sure the transistors in drive systeem are new and 100% ,second step are check the diode in system. If you check this and it is oke with multimeter it is better to swap for new. After this and truck gives C0 , check connectors from transistors to CPU board , if it is 100% oke replace CPU board for new. Test the drive motors with disconnecting of truck and only a 24 volt battery , if rotate correct without any damage it is oke. It is sure you check only the transistors , connectors , diode and least the CPU board. Nothing more can give a C0. Mayby you destroyed one transistor with assembly to truck..
  • Posted 23 Jan 2021 20:20
  • Reply by tr_doctor
  • Netherlands
Regards
There should be no contactor on when you turn the key on until demand by the travel Or pump lever. The transistors All must be replaced in 3's. Check volts to frame. Is the plastic isolator behind all contactors? Hours on unit? Japan drive or GE motor? Any deviations on a contact coil is to be replaced. If you have a known good cpu I would try and swap them. Sometimes a visible fault Or failure is not there. Flight systems handles rebuilt cards.
  • Posted 22 Jan 2021 00:26
  • Reply by ron_k
  • North Dakota, United States
Ron kornkven
We have quite a few 90's era 5FBCU15's. The two other things that have caused the CO issue for me that I didn't see mentioned here is bad main drive motor brushes or problems with the commutator, and the small DRD diode that sits on the connector bars of the TM (main transistors). This DRD looks like a small jumper with a diode that has clear shrink tube around it, both ends have small loop connectors, but one is red. Other than those two, it is usually the MS contactor sticking on or failing, bad TM transistors (I never get the readings the book says so I just look for one that reads different than the other two), and a couple circuit boards.
  • Posted 21 Jan 2021 23:51
  • Reply by CR500R
  • Indiana, United States
Is anyone interested in coming to watch me melt this forklift into a puddle of smoking waste with a large amount of Thermite?

Because i'm beginning to think that is the next logical step in this troubleshoot effort.

Seriously, I have wasted so much time and money on this its not funny. I have hired 4 local techs no results, I have spent over 100 hours looking at it no results. I have replaced practically every electrical/electronic component on the lift.

Everyone says its the contactors. I tested all of the contactors. When that did'nt work I replaced them

I replaced the three circuit boards
I replaced all 6 of the transistor modules on the back panel

The only thing that I can find to make it stop showing the C0 error is to unplug power from the board.

I dont know I might just try to cut the thing up into little pieces with my plasma cutter.
  • Posted 18 Jan 2021 01:27
  • Reply by IMECH
  • Texas, United States
Thanks for your time
Hi, 1.check if traction motors have short circuit or any problems ,2.check 2 tractions transistors for any damage,3.check at display panel connector have voltage up to 36v , if voltage its up to 36v and motors and transitors its good ,have cpu problem ,if voltage at panel its under to 36v ,have problem at dc/sd board
  • Posted 28 Dec 2020 04:42
  • Reply by gus_v
  • Athens, Greece
No suggestions after 3 weeks when it's such a common error code? I was under the impression that was the point of this forum.
  • Posted 27 Dec 2020 05:08
  • Reply by IMECH
  • Texas, United States
Thanks for your time
Does anyone know where the small red and orange wires that are connected to the same terminal as P1 lead to?

Also should I be seeing 12k ohm to frame on the red wire?
  • Posted 15 Dec 2020 04:42
  • Reply by IMECH
  • Texas, United States
Thanks for your time
Hi,its very difficult damage, 1st reason drive motors problem, 2nd reason transistors drive or CPU card
  • Posted 15 Dec 2020 04:34
  • Reply by gus_v
  • Athens, Greece
Ok, well if no one can help through this channel can you recommend a technician that I can call?
  • Posted 14 Dec 2020 06:54
  • Reply by IMECH
  • Texas, United States
Thanks for your time

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