Volvo lighting ECU or whatever it's called

[Big5er]

Ok, first a disclaimer. I have been busy (ie lazy, plus it is 101 degrees and too busy playing in the lake with the nieces and nephews) so no, I do not have the codes it threw so this is basically a post looking for similar issues.

The back-up lights on the Volvo are LED and I also have an LED strip (36" long "Blade" light strip mounted on the new generator box.  The trailer (2018 DRV) has two scare lights that should also light up when the trailer is plugged in. They are incandescent bulbs.

The lights on the truck alone function properly. The scare lights all function as scare lights (ie, using the on/off switch) BUT when I plug the trailer into the truck and the back-up lights come on, they all (truck and trailer) flash one time and go off. The electric ECU throws up the error "check lighting ecu at next stop". The next time they "should" come on it does the exact same thing, they all flash and it throws the error. Unplug the trailer and all is well with the backup lights on the truck. I have heard of the ECU not liking LEDs and needing to be re-programmed but I have never heard of the opposite. Any thoughts?

[DesertMiner]

The “lights” ECM is called the “LCM”. Some LED bulbs are “polarity sensitive” and will only work in a socket that is wired with the correct polarity. Incandescent bulbs are not as sensitive and can work in a socket that is wired with incorrect polarity. Your trailer lights may be wired wrong but still work but not when connected to the truck. The LCM May be “seeing” the wrong polarity or might see it as a direct short. Can you remove the bulbs in the scare lights to see if the bulbs are causing the problem?  Are the scare lights hooked up so they cannot come on when hooked up to the truck? Might be a wiring “disagreement”! Are you using a “Jackalopee” and running the reserve light circuit through it?

[Big5er]

Yes, I am using a Jackalopee and its reverse circuit. All.of the bed wiring is run from the Jackalopee.

Removing the scare light bulbs was my first thought too. But I didnt bring my ladder this trip and doing it from the roof didnt sound fun. As I mentioned, those are incandescent and i didnt "think" that would be a problem but who knows. 

And they come on with the rest of the backup lights. No added switch.

[Darryl&Rita]

Without a ladder, look in the trailers wiring bundle. It should have a relay somewhere to turn on the scare lights via the reverse lights. Pull the relay out, try again. The relay might be in the basement, or even in the box where the umbilical cord ends.

[Alie&Jim's Carrilite]

Phil, Do the lights work correctly on the trailer by themselves using the switch on the control panel?

If they do, then the issue is probably in or on the "Brain" box DRV installs that runs the turn signals, brake lights, etc.  As long as the truck side is working correctly then that's where the issue is.

BUT

Since you just had a bunch of work done, whats the chance there is a rubbed/burned/snagged/stray thread of a wire not in the right place at the truck receptacle?  If not call Slade at RR.

[DesertMiner]

Do DRV’s come wired to activate the “scare lights” when the TV is put in reverse or is this an added option?

Edited August 3, 2019 by DesertMiner

[Moresmoke]

I would guess you are overloading the reverse light circuit. The reverse lights on the truck are on the truck side of the wiring only. There is no reverse light connection on the trailer side of the truck wiring. The LCM monitors the current draw of the truck lights and will fault if out of range. The draw threshold cam be changed in the LCM, but that requires Volvo Tech Tool “the laptop” to do.

Going to leds on the trailer may drop the load enough.

[rickeieio]

Did this all happen since you installed the new generator box?  If so, unhook the box lights and see if the problem still exists.

Edited August 3, 2019 by rickeieio

[Jack Mayer]

12 hours ago, DesertMiner said:

Do DRV’s come wired to activate the “scare lights” when the TV is put in reverse or is this an added option?

As far as I know they all come this way...never seen one that did not.

[Hewhoknowslittle]

The rear scare lights have 2 bulbs each side, one is the scare light, and the other is the reverse light. No magic box on these.

As I recall the backup light portion is a halogen bulb, may be pulling to many amps for the LCM to be happy, but I haven't stayed in a Holiday inn Express lately.

Roger

[Nuke-E]

1 hour ago, Jack Mayer said:

As far as I know they all come this way...never seen one that did not.

I've never noticed that. Are we talking about on the sides of the trailer?  That would be a big no-no.

 

Phil, have a look at the diagnostics menu (scroll down below vehicle messages).  You should be able to get fault codes for the LCM. My first guess is that you either have a short circuit fault on the reverse circuit, or more likely low enough voltage getting to the LCM that can only think like it's drinking caffeine-free Dr. Pepper.  Feel free to post or send me the codes, or give me a call this afternoon and I'd be glad to help you figure it out.

 

[Alie&Jim's Carrilite]

5 hours ago, Nuke-E said:

I've never noticed that. Are we talking about on the sides of the trailer?  That would be a big no-no.

Yes, 

At the rear of the sides at the top are scare lights.  These are wired to come on with the reverse lights on the back cap as well.  

[SuiteSuccess]

4 minutes ago, Alie&Jim's Carrilite said:

Yes, 

At the rear of the sides at the top are scare lights.  These are wired to come on with the reverse lights on the back cap as well.  

All the time or only when the headlights are also on?  I need to have Donna check because I’ve never noticed and she hasn’t mentioned ours coming on when I’m backing 

[Alie&Jim's Carrilite]

28 minutes ago, SuiteSuccess said:

All the time or only when the headlights are also on?  I need to have Donna check because I’ve never noticed and she hasn’t mentioned ours coming on when I’m backing 

According to Alie, ours come on whenever I put the truck in reverse.  

Remember though that I have an old Volvo....1998 Gen 1

[Big5er]

23 hours ago, Alie&Jim's Carrilite said:

Phil, Do the lights work correctly on the trailer by themselves using the switch on the control panel?
Yes, the scare lights work fine on the switch

Since you just had a bunch of work done, whats the chance there is a rubbed/burned/snagged/stray thread of a wire not in the right place at the truck receptacle?  If not call Slade at RR.
I never had backup lights on the trailer UNTIL I ran the wiring thru the new generator box and connected them so I when I installed the new LED lights on the gen box. They were only on the rear of the truck until then.
 

 

12 hours ago, Moresmoke said:

I would guess you are overloading the reverse light circuit. The reverse lights on the truck are on the truck side of the wiring only. There is no reverse light connection on the trailer side of the truck wiring. The LCM monitors the current draw of the truck lights and will fault if out of range. The draw threshold cam be changed in the LCM, but that requires Volvo Tech Tool “the laptop” to do.

Going to leds on the trailer may drop the load enough.
Exactly what I was thinking...TOO many back up lights. 

 

10 hours ago, rickeieio said:

Did this all happen since you installed the new generator box?  If so, unhook the box lights and see if the problem still exists.
I ran the lights through the new box but as I said above, this gets me from two single leds to 2 leds, 2 halogen and the light strip. I'm thinking remove the halogen bulbs in the scare lights and see what happens. If that stops the error, maybe chjange them to led and see what happens.

 

7 hours ago, Hewhoknowslittle said:

As I recall the backup light portion is a halogen bulb, may be pulling to many amps for the LCM to be happy, but I haven't stayed in a Holiday inn Express lately.

There seem to be several of the same opinion Roger

 

7 hours ago, Nuke-E said:

I've never noticed that. Are we talking about on the sides of the trailer?  That would be a big no-no.
Been that way for years on DRV's. That is the only brand I have owned. I just never hooked them up until now.

Phil, have a look at the diagnostics menu (scroll down below vehicle messages).  You should be able to get fault codes for the LCM. My first guess is that you either have a short circuit fault on the reverse circuit, or more likely low enough voltage getting to the LCM that can only think like it's drinking caffeine-free Dr. Pepper.  Feel free to post or send me the codes, or give me a call this afternoon and I'd be glad to help you figure it out.

I'm betting its the voltage...too many lights. I'll probably get the codes to morrow David...too sunburned today

 

[GeorgiaHybrid]

Phil, you have a too long of a wire run that created a low voltage which increased the amperage required and that caused the LCM to shut off the cirduit.

Try running the backup light circuit to a new relay in the nose of the trailer that uses the truck circuit to trigger the relay and the trailer battery and wiring to run the lights.

I had to do that when I added new backup lights to the rear of our DRV as they pulled a littlie to much juice and didn't wotk right until I gave them enoungh voltage.

Remember on a DC circuit length, you have to count the distance out and back when figuring amperage capacity.

Edited August 4, 2019 by GeorgiaHybrid

[HERO Maker]

11 hours ago, Big5er said:

I'm betting its the voltage...too many lights. I'll probably get the codes tomorrow David...too sunburned today

Sunburned!!!!!  Well I see you're fitting right into the lifestyle!!   Good on ya.

[Big5er]

9 hours ago, GeorgiaHybrid said:

Phil, you have a too long of a wire run that created a low voltage which increased the amperage required and that caused the LCM to shut off the cirduit.

Try running the backup light circuit to a new relay in the nose of the trailer that uses the truck circuit to trigger the relay and the trailer battery and wiring to run the lights.

I had to do that when I added new backup lights to the rear of our DRV as they pulled a littlie to much juice and didn't wotk right until I gave them enoungh voltage.

Remember on a DC circuit length, you have to count the distance out and back when figuring amperage capacity.

Well shame on DRV for not figuring that out for those of us that are electrically challenged. Thanks!!

[DesertMiner]

Did you ever find the problem? What was the fix?

[Big5er]

DM, I did as suggested and put a relay inline. I used the power from the 12v charge line and the backup light power as a trigger. It took the extra load from the LCM and solved the issue. 

[DesertMiner]

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