Thomas bus, safety lights + stop arm - program out or mimic with resistors?

[BusBiz]

I have a 2014 Thomas C2 safety liner and I can't get the cruise control to work. Everything seems to be programmed and configured properly, idle control works and I can set it at any RPM and when touching the brake pedal it goes off but when I try to set the cruise control it doesn't go on and set and I think it's because I unplugged the stop arm and 8-way roof safety lights and the system is generating a fault code that's keeping the cruise control from activating.
Has anyone dealt with this problem or have experience with this cruise control issue and or how to deal with it?

 

[ewo1]

What engine you have and what is the fault code?

I have reviewed the fault codes and connector pinouts for the Bulkhead Module (BHM) which is basically your body control module from the - Thomas Built Buses Service Literature: Workshop, Saf-T-Liner C2 School Bus manual. I did not see any specific fault codes listed for either the cruise control settings, stop arm or 8 way lighting (wig wag) system.

If your motor is an international motor then the cruise control setting would be with the engine ECM.
The fact that your idle control functions and deactivates when you hit the brakes...that is interesting.

I would think they would be the same circuit ???

Link for the BHM manual, 30 pages.

https://s3.us-east-2.amazonaws.com/assets.myersequip.com/Downloads/16._c2_54.01_workshop_manual.pdf

Fault Code Information-page 10
The information below contains all proprietary Bulkhead Module (BHM) fault codes for J1587 and J1939 data bus protocols, how to view these codes, and what they mean. The fault codes can be seen on the instrument cluster. The mode/reset switch is used to scroll through the displays on the message display screen.

 

[BusBiz]

2014, 25' thomas c2 safety liner, Cummins, 6.7 Allison 2500, checking for codes today.
All idle control functions are working properly and can set any RPM but cruise control will not engage when moving. Disconnected stop arm and 8-way roof lights..
Looking to mimic arm and lights (with resistors?) or better yet program out the arm and light functions so they won't cause any codes.

 

[ewo1]

2014, 25' thomas c2 safety liner, Cummins, 6.7 Allison 2500, checking for codes today.
All idle control functions are working properly and can set any RPM but cruise control will not engage when moving. Disconnected stop arm and 8-way roof lights..
Looking to mimic arm and lights (with resistors?) or better yet program out the arm and light functions so they won't cause any codes.

What are the codes ???

 

[BusBiz]

Fault 1
Bh33
6918
Fail 7

 

[ewo1]

Fault 1
Bh33
6918
Fail 7

Fault 1
Bh33 - J1939 BULKHEAD (33) ERROR
6918 - MISSING DATA SWITCH
Fail 7 - FAILURE MODE INDICATOR 7.

Interestingly enough, the C2 BHM manual does not clearly identify where this missing data switch is wired or located.

If you look at page 28 of the BHM doc, under Connector B7 Dash Harness Pinouts you will find the connector pin numbers for the associated smart switches.

without actually being at the bus or looking at a wiring diagram, you might want to go back to the wiring you removed and see if any of them go back to those "smart switches".

If none of those light circuits are there, great!

If they are then to go back and try to put an answer to your original question of mimicking with resistors, ...
could it be as simple as adding a small incandescent bulb the the circuit in order to trick the BHM as you are looking to do?

I don't know... More info on the wiring you disabled is required.

This BHM country, just as in the International BCM country.... removing wires/circuits is gonna require more planning!

This is an interesting scenario for sure and looking forward, more folks are gonna walk into this and experience some unique nightmares.

So my question to you, when you disabled these circuits, how did you do it.
Did you simply cut and cap the wires on the "load" side or did you do it from the main electrical panel or the switch panel?

 

[ewo1]

Doing some more research, the Fright liner C2 series also has a "Chassis Module"!
The chassis module works as a slave for the Bulkhead Module.

On the forward chassis harness, you will find the wiring pinouts for the stop arm.

I have no idea if this is your issue or if it begins from this spot... this is all brand new learning territory right here....

Chassis module 54.02

https://s3.us-east-2.amazonaws.com/assets.myersequip.com/Downloads/17._c2_54.02_workshop_manual.pdf

 

[ewo1]

this one begins to put things together.

Switch Hub Module - 54.11

https://s3.us-east-2.amazonaws.com/assets.myersequip.com/Downloads/18._c2_54.11_workshop_manual.pdf

The SHM is used to connect up to 24 Smart Switches to the electrical system, and to control specific inputs and outputs.

The Switch Hub Module is mounted on a panel in the sealed compartment to the left of the driver that is accessible from inside the vehicle. It has nine harness connections, though all may not be used. See Fig. 1.
Smart Switches are connected to the Switch Hub Module (SHM) via intermediate modules called 8-Switch Banks (8S.
Up to 8 Smart Switches can be plugged directly into each bank, and up to three banks can be connected to the SHM, via J5-BANK A, J6-BANK B and J7-BANK C.



Some more read on how the bulkhead operates.
2016 c2 bus ->
2016 c2 switch hub curcuit - School Bus Fleet Magazine Forums

These C2's have smart switches, so it's not a dedicated circuit. The switches determine which circuit the SHM operates. So on the harness side, they should all be wired the same. You could swap switches to see if it's the harness or the switch. Power in on the harness side should be the same as all other switches.

BHM is left frt. fender
CHM is behind left fender under bus
SEM is under your left arm sitting in drivers seat

2011 c2 bus ->
Thomas C2 Bulkhead module - School Bus Fleet Magazine Forums


The module does its work in J1939 but the system will broadcast faults via both J1939 & J1587.
Any codes pulled via dash will be J1587 format.
Service-Link will read the code in both J1939 & J1587 languages.

Got a dash code?

C2 Bulkhead module fault codes - School Bus Fleet Magazine Forums

A quick Primer for the uninitiated.
1. Identify the module.
.....ECU = Engine Control Unit
.....ABS = Anti-Lock Brake System
.....BHM = Bulkhead Module
.....CHM = Chassis Hub Module
.....EXM = Expansion Module (can have multiple)
.....SHM = Switch Hub Module

2. x-ref the SID/PID in the Shop Manual for that module
.....PID = Parameter Identifier
.....SID = System Identifier

3. Identify the meaning of the FMI (found in same manual right after the PID/SIDs)
.....FMI = Fault Mode Indicator
.....FMIs are SAE standardized. They apply to any module, system or parameter

It breaks down to which computer(1.) sees which item(2.) & what it don't like(3.) about that item.

To check the wires feeding a function.
X-Ref the PID/SID to the Circuit-To-Pin (CTP) spread-sheet.
.... from Service-Link & email Contact your TBB dealer, they can make it upil it to you
....Some dealers send a copy with the bus delivery
....CTPs will vary from year to year & bus spec group to bus spec group
Check continuity from the module pin to the function identified on the PID/SID.

 

[ewo1]

I found this electrical diagram dated 2008. This diagram is for the stop arm and wig wag lights.
This diagram shows how they are wired into not only the Switch hub module but also the chassis hub module. Your wiring might be same or very close?

https://www.thomasbusonline.com/manuals/part_dwg/149128B.pdf

 

[ewo1]

Switch Hub Module (SHM) Troubleshooting Guide

This Carolina Thomas Bus Buzz is two parts and intended to provide you with information on how to troubleshoot the C2 Switch Hub Module.

This component is commonly rejected on warranty claims as it is misdiagnosed. If you use and learn this you can be the sharpest technician in your county.

This Bus Buzz should accompany troubleshooting spreadsheet as these are photos to assist your efforts on component identification

 

[ewo1]

This doc explains really well, in simple terms....

The C2 system was designed for school busses and the M2 for heavy trucks, which is much more robust with options and features.

Use this manual to learn about the basic features and grow from there...

M2 Multiplexing - The Basics • What is Multiplexing??
• Basic M2 Multiplex Components
• Multiplexing Programming Example
• M2 Resources

 

[nikitis]

Fault 1
Bh33 - J1939 BULKHEAD (33) ERROR
6918 - MISSING DATA SWITCH
Fail 7 - FAILURE MODE INDICATOR 7.

Interestingly enough, the C2 BHM manual does not clearly identify where this missing data switch is wired or located.

If you look at page 28 of the BHM doc, under Connector B7 Dash Harness Pinouts you will find the connector pin numbers for the associated smart switches.

Just a thought, is "Data switch" just their way of saying a software switch in the ECU?

Even the early 90's buses with the first computers, had this software switch to enable Cruise Control.

 

[ewo1]

Just a thought, is "Data switch" just their way of saying a software switch in the ECU?

Even the early 90's buses with the first computers, had this software switch to enable Cruise Control.

I was wondering the same thing.

This system is a whole lot more complex than the international BCM...
It seems that most all Thomas busses from 2007+ will have a BHM so removing wiring is gonna be a whole new world for Freightliner chassis busses!

 

[ewo1]

I was wondering the same thing.

This system is a whole lot more complex than the international BCM...
It seems that most all Thomas busses rom 2007+ will have a BHM so removing wiring is gonna be a whole new world for Freightliner chassis busses!

I have read that for the "Smart Switches", you need dealer software to reprogram the switch options. similar to the International BCM.

I'm thinking "data" switches are the physical switches but, they are not your standard type Dpdt switch. I believe they might have resistors built into them... I am still reading and figuring this all out.

After reading some...seems like the resistor value might be software assigned by the BHM, not 100% sure on this yet...

to the OP....

you got one heck of a learning curve here!

 

[ewo1]

SMART SWITCH- This is what it is...

• Smart switches are optional low-current switches that are connected
to the Bulkhead Module (BHM) or to an optional Switch Expansion
Module (SEM) on a Business Class® M2 vehicle. A smart switch is
used to activate an optional feature on the vehicle.

• A smart switch is significantly different from a high current switch.
Unlike a high-current switch, the smart switch is designed to control
very low currents, and will be damaged if it is connected to a high current
circuit. A smart switch has an internal printed circuit board
which contains:

• A light-emitting diode (LED) for backlighting the switch when the
headlights are turned on;

• A light-emitting diode (LED) that, when on solid, indicates the
feature is activated and, when blinking, indicates an error
condition.

• Two precision resistors that are used to create a unique switch
identifier that allows the BHM to identify each switch that is
connected;

• Three precision resistors that are used to indicate the position of
the switch.

• Reference Parameters are linked to resistive value of a Switch by the
BHM

 

[ewo1]

@BusBiz,

I am wondering if your solution is as easy as re-programming your BHM?​

Any other mods like adding resistors, without fully understanding the Multiplexing architecture and programming limitations.... well let's just say your bus would be the TEST DUMMY!

 

[nikitis]

My money is on software enablement.

 

[ewo1]

This doc is really full of lot's of info on the design and operation of the multiplexing system.
It is written for the M2 platform.
The C2 is a simpler version but the architecture rules and protocols should be the same. It all software driven!


This guide shows ALL the pinout locations, voltages/signals, fuse locations and also contains high current circuit schematics too!

This is a must have if you have a BHM system on your bus!



ELECTRICAL SUYSTEM OVERVIEW
2007 M2 ELECTRICAL

BODY BUILDER REFERENCE GUIDE
​

 

[ewo1]

This is the 2010 version of the same guide.

ELECTRICAL SYSTEM OVERVIEW
2010 M2 ELECTRICAL

BODY BUILDER REFERENCE GUIDE​

 

[AlphaHare]

@ewo1 - the depth of your help is just epic. It's one of things that make this an interesting forum. I don't even have an International and it's worth saying thank you!