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Discussion Starter #1 (Edited)
My tail light's been out for a month and I need some sort of diagram or service technician's manual to begin to trace my short.

(Updated with resolution): The dealer diagnosed it for $125 and sold me the inner housing ($77) which I installed myself. Six months later and the light was out again, but this time it was just a bulb. Three more months passed and the same light was out. After nearly getting ready to get rid of the car after an argument with the service dept of the dealership--and my thinking it was going to require me to replace and program the PCM---I happened to fix it when I disconnected the battery cable, inadvertently resetting the computer.
Strange.
 

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VERY VAGUE!

Is just ONE out, ALL out, one SIDE out, TRUNK ones out, BODY ones out?

I have not been able to find the fuse layout for my 2015 either.

A Short would blow a fuse somewhere, and since you can't find the
fuse, you don't know if it is a short, so you can't test for a short.

You will have to pull each and every fuse to check them. I had to do it...
Make sure you put each one back where it came from.
 

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Discussion Starter #3
I did pull every single fuse and they all checked out. I suppose I could pull them all again but I thought it can't be a bad fuse since the connector is getting 1.3 volts (while the LH connector is getting 12.1 volts and working properly.)
 

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So the RH (passenger) side is out, all lights, including the ones on the trunk lid?
Does that also include the RH side brake light? RH Turn Signal? RH Reverse? Do
you get the fast blink on the dash RH side turn signal? You're still being unclear.
When you say RH side tail lights, we are to assume EVERY single one, including the
ones on the trunk lid. Or is is just the RH side outer tail, the one in the body, and
not any lights in the trunk lid tail on the RH side. They're two separate plugs,
plural, and you said plug, singular. This may help if someone else had this
issue...

There is no short, a fuse would pop, and no voltage anywhere on that side.

More then likely, it is a module. If you were under warranty, the dealer
would take care of it under the 3/36 warranty.

VCDS would also tell you if there was a problem somewhere.
 

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Discussion Starter #5
2015 Jetta S 2.0L naturally aspirated sedan (without LED)
There are two failures of my tail lights which I believe are completely independent problems:
1) RH Tail Lamp Assembly failure (inner assembly located on the folding trunk door)
I'm only getting 1.3v at the electrical connection. Yes, the bulbs are fine, and I even confirmed that the assembly works on the LH connector so we know that both the bulbs and their socket plate are fine. I've checked every single fuse under the hood and in the LH interior fuse panel but can't find a 2015 fuse diagram. Does it seem that I have a short somewhere in the system? Any common problem portions of the harness if so?
2) reverse light on internal housing is working, something I didn't earlier note

### (The following is revised because it is no longer an issue; it's been fixed by securing the bulbs and/or resetting the ECU by touching the negative and postive battery cables together for a hard reset.

2) RH tail light scoket (outer assembly) failure
(SOCKET PLATE - VOLKSWAGEN p/n 5C6-945-258-A) :
The outer tail light housing assembly seems to be a simple mechanical failure since the two-filament blinker bulb works but the continuous bulb won't come on. Of course I tried replacing the bulb and even connecting the housing to the LH connector, but the same persisting problem indicates the lighting socket assembly needs to be replaced, despite my attempts at cleaning and bending the contacts.
###

Thanks for any help!
 

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Your light switch, take that out and look and see what one you have,
one with a LARGE 17 pin connector, or the small 10 pin connector.
The large ones have separate left and right parking light pins... The
The smaller 10 pin is one pin for all parking lights. If it is the large
one, it can either be the switch, or a loose wire at the harness. If
it is the smaller 10pin, then it won't be the switch so you can rule
that out.

To remove to look:
Lights off; PUSH the lever IN, turn right, and it unlocks from the socket, pull the assembly out.
The lights will be on, you can turn them off now.
Look at the plug, then you can just push the assembly back into the hole.

Oh, is the front right side-marker in the headlamp also out?

Do you have the bulb out dash warning light?

Did you attempt the "10 second battery disconnect, to RESET everything" and hope
it works?
 

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Discussion Starter #8
Thanks.
I have the 10 pin connector.
YES The front RH side marker is out.
YES The instrument cluster is showing a lighting error bulb.
I disconnected the battery but when I reconnect, strange things happened with rear tail lights: the outer and inner RH tail assemblies lit up for but a moment before going out again.
 

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So, we can then eliminate the switch then.

Pull the plugs, one at a time, from the rear tails, and check that front marker,
see if it comes on after one or both have been disconnected. This will eliminate
a short at the tails.

More than likely, it will be a BCM... Is your 3/36 warranty still in effect? Or, if
used, your certified 2/24? The precertified also covers everything, with a $50.00
deductible. I just had a door latch replaced last month under the 2/24 precertifed.
 

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Discussion Starter #10
You lost me with 'pull the plugs'. You mean the electrical connection to the socket plates?
Unfortunately we're over 60k miles.
 

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Yes, the 4-position harnesses at the PCBoards of the lights.

Pull one, turn the lights on, check the front marker.
Turn off, Pull the other plug, turn on, check front marker.

This will then eliminate the possibility of a short at the tails.

Still, with 1.3V, I am thinking BCM...

Not sure, on some models it was a faulty relay.

Without VCDS to check the Central Electronics module, this can take
forever to diagnose. HOWEVER, you can, run another wire back to the
lamps and power the parking lights with a switch till you get it fixed.

I ran a wire back there to independently power the reverse lights with
a switch, so, I know it can be done. I have a 2015 Jetta 1.8 TSI Sport.

Have you checked the fuses in the engine compartment? Who knows what
they have changed since 2013. Your small fuses, behind the dash, are on
the RIGHT side, yeah? My 2013, they were on the left side. This 2015,
they're on the right... I know they changed the positions, because
on mine; top left, top row, 2nd fuse in, is high beam power. On the 2013,
that's not where the hi-beam fuse is on that block... I can't find any
fuse designation on the MK6 for parking/runnng lights.
 

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Discussion Starter #12
View attachment 34962 FullSizeRender_1499053562964.jpg FullSizeRender_1499053570210.jpg FullSizeRender_1499053581325.jpg View attachment 34962 FullSizeRender_1499053562964.jpg FullSizeRender_1499053570210.jpg For some reason, my post is getting held for moderator approval. Anyhow, I've got pics to upload showing the lights in the various stages
I'm still not following. Are you indicating to tear apart the clip and remove each of the four wires?
When you say 'PCBoard' I'm inferring Socket Board, VW p/n 5C6945260B.
I tried unplugging the main connector to both the internal and external tail light housings, but the front RH side marker is still OUT. I'm going to check the bulb to make sure it's not just a bad bulb.
 

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Discussion Starter #13
Yes, the 4-position harnesses at the PCBoards of the lights.
You mean to rip apart the clip and pull each of the 4 wires? I don't think I'm understanding 'PCBoards' - do you mean socket board VW p/n 5C6945260B?
Without VCDS to check the Central Electronics module, this can take
forever to diagnose.
I've got OBD2 gear and programs for BMW and Ford but this is our first Peoples' Wagon.
HOWEVER, you can, run another wire back to the lamps and power the parking lights with a switch till you get it fixed.
Is 18 gauge too thick? It's the only stuff I have handy.

I ran a wire back there to independently power the reverse lights with
a switch, so, I know it can be done. I have a 2015 Jetta 1.8 TSI Sport.
Yes, that's how I found you. That's a handy DIY indeed.

Have you checked the fuses in the engine compartment?
Checked em' all.
Who knows what they have changed since 2013. Your small fuses, behind the dash, are on
the RIGHT side, yeah?
Yes
 

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No, I just said unplug the lights, not remove any of the wires. The plug
has four wires in it, and it unplugs from the light's PCBoard, what you call
the socket board over circuit board, heh heh...

Ahh, so, when the car is running, the lights on the right side go out? Is
The front marker also on when the engine is not running, and it goes out too?

That is the module then, because when the car is OFF, there is solid power
to ALL the lights when sent. However, when the car is running lots of it
switches to Pulse Width Management (PWM), and a module is responsible for that.
Brakes are also controlled by a module, but there is an option on mine,
in VCDS to turn that off, don't know if that means it relies strictly
on the brake switch then, or not... The CENTER tail is a completely
separate circuit, and I have had to wire tail brake lights to the center
tail to bypass a module. The center brake light is usually right to the
brake switch at the brake pedal.

For your parking lights in the trunk lid: I would run one wire over (jumper) from the left
tail's parking light power wire, to the right side parking power wire. JUST the power wire,
the grounds are not switched. This will then keep those working. You will need a separate
one for the body mounted tail... I mean, this is, until you get it fixed, or what not...

18GA wire is fine, I used 22GA for my reverse light switch thing.
Don't touch the reverse if that works as normal.

I had problems with HIDs in my car for the same reason. They would work
fine when the engine was not running. As soon as I turned the engine
on, the HIDs would flicker, then go out. I put a relay on, and it would
buzz when energized, that meant, power went from solid to PWM with
the motor running. Low beams too, so I had to parallel a 470uF capacitor
on the coil to stop the sharp (saw tooth wave) power curve used with PWM to a
curved (sine wave type) pulse to keep the relay latched. HI-beams work
fine now... PWM sucks... It's supposed to lengthen bulb life...
 

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Discussion Starter #15
Re: trunklid tail: ok, I'll proceed to hot wire this and report back.

Re: PCM: I can't find anything on Pelican Parts, ECS, FCP Euro, or any of the usual suspects. Is it something only found through the dealer or used through eBay, etc?
Is it VIN-specific or does it require VCDS to program? Or is it Plug and play?

Re: PWM: Hmm, its been too long since I took trigonometry for me to fully grasp sines as they apply to pulse wide mgmt.

Re: one other variable eliminated:
There has been a development since my last reply on the this thread: I discovered an aftermarket GPS tracker of sorts spliced into two wires connecting to the OBD2 port. (We purchased from a used car dealer who did disclose this at time of purchase.) I don't suspect this caused any of the issues, but I disconnected it and cleaned up the wires to eliminate any variables.

Re: front RH cornering light: this is out at all times (while the LH cornering light works fine.) I need to get back there and check the bulb.
 

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This is a 2015 Body Control Module (BCM/CECM):


LH side, under the dash, maybe behind the fuse/relay center,
to the left of the pedals, up.


The older ones have three plugs, and the 2015 GLI looks like it has three.

VCDS sees it as the Central Electric Module.

As I said, if the parking lights are working with the motor OFF, then it has
to be the CECM when it takes control of the lighting with the motor on.
 

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Well, the mean time, you'll have to jumper the left side to the right, for
parking lamps. If your brake and reverse and signals are working, then
that will be it. Else, you can jumper from the center brake to any
effected brake light. Been there, done that...

Yeah, I did not mention reseating, because they work when the
engine is not running.
 

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Discussion Starter #19
The BCM costs more than $500 from the stealers, and they want to slap on a fat tip for installing. Looks like I mind as well purchase a used BCM for $100, then gear up with VCDS to program it, no?

Firing up the soldering iron to hot wire this light this morning.
 

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I would solder plugs to jumper your lights, so you can remove the jumper
easily when/if you get the BCM. Soldering, you can cut it, and then tape
over it though...

You will need to access the CECM, and write down the LONG CODING
stuff, for example:
Address 09: Cent. Elect. (J519) Labels: 1K0-937-08x-09.clb
Part No SW: 1K0 937 087 G HW: 1K0 937 087 G
Component: BCM PQ35 H+ 103 0572
Revision: 00103 AE
Coding: 6D180A1E90272A0480080081700005C441010086434D8D6064 8020200000
Shop #: WSC 01357 011 00200
VCID: 354FFB8E9C2080B0C2A

That will need put in the CECM you place into the car. Highlight and COPY it,
paste into a TEXT editor (notepad) & save. Then, when you put the replacement
CECM in, load and COPY it from notepad, and paste into VCDS.

Make sure the battery is disconnected when you do the swap.

Also, with part numbers? Say yours is 1K0 937 087 G, you need the same
part number, including the G if possible. If you get one with a J, it
is a later revision, not sure how it will act, but VCDS should still be able
to program it with your copied code.

DO not get a EUROPEAN model, your remotes won't work, different frequency.

CECMs with 315 MHz radio key/carrier frequency (USA) end with the letters A, C, E, G, J, L, N.

SO, one with a Q will not work for you...

Here is a replacement example, with CVDS screen shots:
http://www.team-bhp.com/forum/diy-do-yourself/169586-vw-polo-diy-upgrading-bcm-body-control-module.html

This is a European model, if course, but the procedure is the same.

FACTORY mode is only if you ordered a brand new one, that has no programming.
 
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