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Old 02-04-2016, 03:20 PM   #1
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LCBU (Light Bar Control Unit) flashes and goes blank.

This is for a 2013 Winnebago Journey 36M but I imagine it applies to many of the Freightliner chassis and possibly other company chassis as well.
This unit is also known as Instrument cluster and drivers information module.

My LBCU flashes on momentarily then goes blank and there are no working gauges or alarms. If I power off the ignition and wait a minute or so it will flash again and go blank.

I have attached the pin out for the connectors on the LBCU.

First I looked for any tripped circuit beakers or blown fuses. There were none but I also was no able to determine exactly which breaker or fuse might be powering the unit so this wasn't very satisfying and didn't seem very likely since the unit comes on every time but only for a second.

Next I decide to see if any gauges were the problem.

The LBCU drives the gauges via a bus that starts on the LBCU as a four pin connector and on my unit daisy chains from one gauge cluster to the next.

Disconnecting the output of the LBCU to the gauges eliminating all of the gauges from the system. This did not correct the problem. The gauges are not (the only) source of the problem. If disconnecting the gauges had worked it would be a simple mater of connecting one gauge cluster at a time to see which one was causing the fault.

Next I chased my tail trying to see if I could spot any power or ground problems to the LBCU that might provide intermittent power this didn't produce any findings.

I should have done this from the start, but it finally occurred to me to get the pin out for the connectors on the LCBU. See attached. Now I can check power and ground at the unit.

My connector has a tab that functions as some sort of pin retainer on the LCBU connector. This has to be removed to probe the pins when it is connected. Mine comes off by squeezing little catches close to the connector.

With access to the wires from the back of the connector I tested with the unit connected to the coach. I used a test lamp to verify that the 12v battery and 12v ignition worked grounded to the chassis. I did the same test grounded to the connector grounds.

Next I tested the resistance from the connector grounds to the chassis.

Finally I used a multi meter to make sure the voltage stayed up when the unit was powered on and that the grounds stayed low when powered up. This establishes that the unit is properly powered and the only faults left are from one of the many data lines coming in or the unit.

After consulting with Freighliner 24/7 support the conclusion was that the LBCU is bad and should be replaced. The unit is reportedly covered by the 36 month warranty so I am taking it in for service shortly.

I would strongly advise any one with problems with this unit to methodically disconnect the gauges and check the power at the pins before chasing loose grounds. It is a lot easier.

I'll update this when I get back from service.
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Old 02-05-2016, 01:32 PM   #2
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LBCU (Light Bar Control Unit) Failure

The title has the wrong acronym and I can not edit it so I'll just post this reply with the correct acronym.

As a follow up, the Freightliner service center Lou Bachrodt Pompano agreed that the unit is bad. It is covered under warranty but I'll have to wait a few days for it to get shipped down.

We will see if a new unit fixes the problem.

I think I'll look into getting a laptop packaged that can substitute for this unit as a backup.

The price for the part would have been about $550.
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Old 02-05-2016, 03:44 PM   #3
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VMSpc by Silverleaf, is GREAT
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Old 02-05-2016, 04:32 PM   #4
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The LBCU controls EVERYTHING on the dash panel.
Stuff that Silverleaf would probably not indicate.

Even turn signal indicators and all of the warning lights ("Wait to Start", DEF gauge, etc.).

The J1939 bus passes through the LBCU to the gauges , that is the 4pin bus you found.

Nothing wrong with Silverleaf, but it won't completely replace the LBCU.

Did Freightliner agree to program the odometer mileage for you before shipping??

Regards,

Dan
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Old 02-06-2016, 06:21 AM   #5
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Will investigate VMSpc by Silverleaf

I'll have to check out Silverleaf it gets a lot of references. First step will be to dig out the connector identification and see what connector my chassis has.
It is an XCL with a build date of 12/14/2012.

It may not show everything but having the engine vitals will be a lot better than driving blind.
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Old 02-06-2016, 06:42 AM   #6
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Thank you for the comments on the J1939 data.

dpinvidic, thank you for the response.
The service tech said it would sync up automatically.
Well see if the service tech takes the time to set the date and time.

After your comment on the non J1939 data I went back to the connector pin out and looked at all the lines.

J1939 seems to be on just two lines as + and -.
Wonder if that is it a current loop or voltage signal? Hope it is current since there is no shielding.

I think I'll write freighliner and see just how much they will share on the electrical of this thing.

Of course even with a service manual for my 1987 FJ60, which is about as simple as it gets, identifying wires in it's relatively tiny harnesses is till a challenge for me. Is that green with red, or red with green, or is that orange not red?
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Old 02-06-2016, 06:54 AM   #7
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I had similar symptoms on my 2014 Excursion the first time I drove it. I took it to the dealer and they re seated the cable harness connector at the rear of the instrument cluster and it never reoccurred. I assume you tried that?
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Old 02-06-2016, 12:46 PM   #8
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Quote:
Originally Posted by cruizerEd View Post
dpinvidic, thank you for the response.
The service tech said it would sync up automatically.
Well see if the service tech takes the time to set the date and time.

After your comment on the non J1939 data I went back to the connector pin out and looked at all the lines.

J1939 seems to be on just two lines as + and -.
Wonder if that is it a current loop or voltage signal? Hope it is current since there is no shielding.

I think I'll write freighliner and see just how much they will share on the electrical of this thing.

Of course even with a service manual for my 1987 FJ60, which is about as simple as it gets, identifying wires in it's relatively tiny harnesses is till a challenge for me. Is that green with red, or red with green, or is that orange not red?
J1939 is a differential pair. But I would not be concerned with that.

Just providing +12, Ground, and I think a +12V ign. signal should make the LBCU boot up and go through its startup sequence. Then it would tell you "No J1939 Data" if there was a problem with the CAN bus.

On mine, the date & Time is lost when I disconnect the chassis batteries.

I will try to post some schematics from the Freightliner sight if you think that would help you.


Regards,

Dan
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Old 02-07-2016, 06:23 AM   #9
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Yes many times.

Quote:
Originally Posted by jondrew View Post
I had similar symptoms on my 2014 Excursion the first time I drove it. I took it to the dealer and they re seated the cable harness connector at the rear of the instrument cluster and it never reoccurred. I assume you tried that?
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Old 02-07-2016, 06:28 AM   #10
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Not necessary, I have what I need for this problem and have a request out for more drawings as well for the next chassis wiring problem.

I really hope to get the necessary information to figure out with fuse, breakers, and relays drive what systems. The labels that are present are ambiguous at best.
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Old 02-17-2016, 08:02 AM   #11
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LBCU replaced under warranty

The unit was at fault and replacing it fixed the problem.

The unit was replaced under the 3 year chassis warranty, which saved $500 according to the service tech.

The unit synched up the odometer.
I didn't bother with the date and time yet.

I downloaded all of the wiring data I could from accessfrieghtliner but they are in a format that requires an app and I could find no way to print them as PDFs.
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Old 01-13-2020, 12:48 PM   #12
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I'm not so lucky

So my 2014 Dutchstar is having the same issue with the warning lights and gauges and Freightliner Help is pretty sure it's the LBCU. I will need to purchase a new one! Where exactly is the LBCU? Is it actually part of the LCD display and warning light panel?
Thanks for any answers.
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Old 01-14-2020, 08:41 AM   #13
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Quote:
Originally Posted by moleman1 View Post
So my 2014 Dutchstar is having the same issue with the warning lights and gauges and Freightliner Help is pretty sure it's the LBCU. I will need to purchase a new one! Where exactly is the LBCU? Is it actually part of the LCD display and warning light panel?
Thanks for any answers.
Be careful here. The LBCU is the rectangular display which changes when you use the control joy-stick button. The gauges are completely separate.
There is a two wire interface (called CAN Bus) which is daisy chained to each gauge and LBCU. I am pretty sure the gauges should work independently of the LBCU. Each gauge and LBCU have a 4 pin connector. Check for +12 & Gnd before you jump in and replace the LBCU. Do the gauges light up when the headlights are turned on??
I'll attach a wiring diagram of the gauges.

Dan
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