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Derek Neustaeter
Derek Neustaeter,
Category: Medium and Heavy Trucks
Satisfied Customers: 4
Experience:  Heavy Equipment Technician at Warner Industries
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I have a blue bird vision bus with the complaint of comm

Customer Question

hi i have a blue bird vision bus with the complaint of comm fail, cat engine installed, we replaced engine ECM, checked all wiring harness found ok, still the problem exist, please help me to solve this issue.
cluster showing : comm fail
Submitted: 1 year ago.
Category: Medium and Heavy Trucks
Expert:  Jeremy replied 1 year ago.

My name is ***** ***** I will assist you.

The vehicle starts? Usually the comm. failure is due to the cluster failing and not always the ECM. It can also be the body controller. Have you connected a computer to the truck to see what codes you have in the vehicle controller? Being a Blue Bird, use GM or JPro to pull codes on the vehicle module.

I'll need the VIN to see if I can pull up a manual for you.

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Customer: replied 1 year ago.



Expert:  Jeremy replied 1 year ago.

This vehicle does have the multiplex system on it. You will need to use a computer to diagnose. However, I will upload the service manual for you which has the electrical diagrams and troubleshooting for the condition you are having. With the no communication on the dash, I would start with the dash module if the engine will start. If it will not start, then I would check the chassis module. I state this for you already checked the ECM.

Without having a computer and not being able to see the bus, hands will be tied and the process will be slower and just checking module to module.

CLICK HERE to the folder that has the manual. Just download the manual, which is split chapter by chapter, to your hard drive.

Expert:  Jeremy replied 1 year ago.

I'll know when you have pulled this. The link is only good for about 7 days so be sure to get it by then. If you need it active again, let me know and I can reset it.

Customer: replied 1 year ago.

engine is starting and running fine, i replaced engine ecm, dash board, still same. when this problem occured vehicle speed derate and dash board all light and gauges going off, abs light on.

Expert:  Jeremy replied 1 year ago.

Sounds like a ICU module (which is the cluster) or the VCU (Vehicle Chassis Module) fault. With what you just described, I'm leaning more towards cluster fault.

I'm presuming you have all the lights, but none of the gauges work, except maybe the fuel, right? If so, then I would remove the cluster and clean all the pins on it. Behind it will be a black, gray, or white box. That will be the module for the cluster that tells the cluster the speed of the bus. It is sometimes referred to as the VSSM module. Make sure there are no broken wires, burnt wires, etc. Clean the connectors on it, plug it all back up, then see what it does. Make sure to use electrical contact cleaner and verify all the pins are pushed in.

If the problem remains, then on the back of the cluster, the plug with it facing you how it goes in the cluster, the top right, see that you have voltage on it and the 3rd to the left from there, verify ground. The rest should be signal wires and the diagram will define which is which. Those 2 are the wires off the J1708 multiplex system. If you have power and ground on them, then the issue is the cluster itself. It can be getting the information, but the module may have lost it's programming due to a bad EEPROM chip in the cluster and can't read the information correctly. If the bus goes off-road at all or a bumpy highway, when reinstalling the cluster, use some double stick Styrofoam type tape behine the mount points on the cluster to prevent it from getting the shock from the road to make it last longer. That is what makes those EEPROM chips go bad in them, bumps in the road and vibrations.

Customer: replied 1 year ago.

i already checked all the things above you said, new cluster also replaced, i checked with CAT ET its showing 231-14 transmission datalink derate and abs light always on cluster showing COMM FAIL.

i tried to replace one EECM from another vehicle now its fine and then again replace the vehicle original ecm the problem start again. subject vehicle ecm is newly parchased and program copied from old ecm.

Expert:  Jeremy replied 1 year ago.

I'm going to opt out and see if I can locate another expert who might have seen this before.

Expert:  Derek Neustaeter replied 1 year ago.

Hello, My name is ***** ***** I'm a registered Heavy Duty Mechanic. Lets see if we can get your concern sorted out, sounds like a tricky one!

Whenever I have encountered a communication error, the first place I go is to the batteries. If the modules are not supplied with a very consistent 12-15 volts, they can have many different types of communication errors. Lets start with the batteries. Remove all of the battery cables, clean the posts, and all cable ends till they are clean. Now load test each individual battery. Each battery must maintain 9.5v to pass. Replace any failed batteries. Connect your battery cables and tighten well. Next find your grounds to the frame and to the engine. Remove them and buff them until clean and reinstall. Also remove your battery connection at your starter and clean thoroughly. Clear your stores codes and check to see if they are still active. If they are still active I would check the power supply to the engine ECM as well as the Cluster.

If you problem still remains, I would be more then happy to walk you through some more steps to solve this issue. Hope this helps!


Customer: replied 1 year ago.

hi dear derek, i have replaced 3 new batteries and cleaned all connections yesterday, after that also the same complaint exist,abs light continuous on and comm fail display in dashboard. when check with ET its shows transmission data link derate complaint 231-14, i am in too much pressure please help me to sort out this issue.

Expert:  Derek Neustaeter replied 1 year ago.

Did you check voltages to your ecm?

Customer: replied 1 year ago.

yes, 12v is there,after start the engine 14v is there.

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