[ChriberV8]

Hello! New to the forum, and new Touareg owner. (2003 V8).

I have encountered a very strange brake light problem.
My right rear brake light stopped working (legislation station pointed this out + got 6 weeks to fix before not allowed to drive).

So, I bought new bulbs.
None worked. (still normal back light and indicator worked. Also brake light left rear and 3rd brake light worked fine).

I got the multimeter:
Measured connector, then the backplate connected to the connector (where bulbs are mounted). Power on normal rear back light lead.
And when braking power on the break light lead (!?).

I switched to a spare bulb backplate.
Same result (!).

And for Both backplates, as soon as I put the bulb in the backplate, the rear back light is litten, But, the brake light does Not work when braking!
I tried to get the backplate leads push up much more forcible to the bulb leads, but no difference.

When I measure the brake light lead, without braking, I get a strange result. 4-5V on the Multimeter.
Now, it would be possible to have a diagnos bulb test this way, but is this not a bit far fetched?
It would be as easy to make the diagnose run when brake pedal is depressed, and when 12V is applied to the bulb?

Another thing is that, the indicator chime/tick has disappeared, and at the same time I get no more warnings in display for broken bulbs.

Anyone having any idea of what this could be?

• ECU locked up? (does any ECU run the rear brake lights?)
• Diagnose ECU not working that interferes with the function?
• The 4-5V shall not be on the lead for the brake light when no brake is depressed, indicating short circuit on the wire harness?

I would be very happy if anyone has any similar experience, and clues to what could be wrong!

And,
What a community! Impressive!

/Christian

 

[jeffnhiscars]

I'm not following exactly what's happening so I can't say if you might have a short or just a bad connection. I doubt it's a control module and my gut says check the contacts where the bulb goes in. The spring tabs may be bent or it's not grounding properly for example. Use nickel plated bulb bases not brass. Osram is your friend

 

[Treg-V-eight]

What bulbs did you get and use? Only the P21 4W ones will work.
If you have correct ones, then check the where the plastic w/metal leads mount to the light assymbly as I believe there are some small screws or connections that hold this together that may have come loose or broke and need some attention. I had to run a screw in mine to hold the plate in place for good contact as I had tried to replace the bulb multiple times to find out it was the connection.

 

[ChriberV8]

I'm not following exactly what's happening so I can't say if you might have a short or just a bad connection. I doubt it's a control module and my gut says check the contacts where the bulb goes in. The spring tabs may be bent or it's not grounding properly for example. Use nickel plated bulb bases not brass. Osram is your friend

Thank You for Your reply.

Yes, I check the spring leads. I also tried raising them (loading with mor force to the bulb). Checked the bulb position to the leads.
They Are worn. But I expected to see bulb at least blinking when wiggle it if so. But Nope. It is strange since I measure 12V at the spring leads if depressing brake. (and 4-5V if Not depressed!).
I will try brush the lead surface at the weekend. Also to disconnect battery for a while if something is stuck/locked.

 

[ChriberV8]

What bulbs did you get and use? Only the P21 4W ones will work.
If you have correct ones, then check the where the plastic w/metal leads mount to the light assymbly as I believe there are some small screws or connections that hold this together that may have come loose or broke and need some attention. I had to run a screw in mine to hold the plate in place for good contact as I had tried to replace the bulb multiple times to find out it was the connection.

Hello Jeff,
Thank You for Your reply.

Yes. That is a good point.
It seems the grounding is good since the normal back light (in the same bulb) is working fine, i.e. grounding leads at the plastic seem to work.
(and the 12V for the ordinary red back light). But Not the brake light, as soon as I put it in.
I tested with a 2nd spare plastic back plate, and it had the same results.
(it would be my normal luck though, if both are broken/bad in the same weird way ).

I will check this further in the weekend. Thanks!

 

[ChriberV8]

Hello! New to the forum, and new Touareg owner. (2003 V8).

I have encountered a very strange brake light problem.
My right rear brake light stopped working (legislation station pointed this out + got 6 weeks to fix before not allowed to drive).

So, I bought new bulbs.
None worked. (still normal back light and indicator worked. Also brake light right rear and 3rd brake light worked fine).

I got the multimeter:
Measured connector, then the backplate connected to the connector (where bulbs are mounted). Power on normal rear back light lead.
And when braking power on the break light lead (!?).

I switched to a spare bulb backplate.
Same result (!).

And for Both backplates, as soon as I put the bulb in the backplate, the rear back light is litten, But, the brake light does Not work when braking!
I tried to get the backplate leads push up much more forcible to the bulb leads, but no difference.

When I measure the brake light lead, without braking, I get a strange result. 4-5V on the Multimeter.
Now, it would be possible to have a diagnos bulb test this way, but is this not a bit far fetched?
It would be as easy to make the diagnose run when brake pedal is depressed, and when 12V is applied to the bulb?

Another thing is that, the indicator chime/tick has disappeared, and at the same time I get no more warnings in display for broken bulbs.

Anyone having any idea of what this could be?

• ECU locked up? (does any ECU run the rear brake lights?)
• Diagnose ECU not working that interferes with the function?
• The 4-5V shall not be on the lead for the brake light when no brake is depressed, indicating short circuit on the wire harness?

I would be very happy if anyone has any similar experience, and clues to what could be wrong!

And,
What a community! Impressive!

/Christian

Small update 5th of February, (Snow outside, and no garage):

I took the plastic backplates, with the spring tabs, and had a more detailed look at them.
Both the original and the replacement backplates, with new bulbs in.
Put power on the connector leads, and both worked fine (unfortunately).
So problem is prior to the rear lamp module.

Finding a schematic, also indicating the Fuse is actually feeding the whole right rear light side, thru J393.
And since both the rear light and indicator works when mounted in the car I conclude it is Not the fuse.

(SB15)
Fuse - SB15
Next step will be to find the J393, and the pins T12c/12 and T12b/11.
It will require some tear down work

 

[ChriberV8]

A little time since I started this thread, now Continuing from last post 5th of February,

Tearing down the side of the car on my Touareg, showed to be a bit more time consuming than expected, especially without breaking too much, no garage, snow outside, dark and stiff fingers in cold. I will not go into the details of the interior, more than that the workshop manual, sucks.

I got to the connectors to the J393, found and disconnected the ECU box from the connectors revealing and making the pins mentioned above in previous post accessable.
Ringing the leads to the bulb connector plate, and there was No issue with the cables. Worked fine.

I had only a few weeks to legislation check attempt no 2. Otherwise it would be banned from traffic until issue fixed.
So I ordered a part from disassembled cars, and ECU with HW Part No 7LO 959 933 C.

Got it in a couple of days.
I turned out, that my soft close trunk, did no longer work. It never fully closed.
Ah, it did not have 2nd row text under the HW part no, that said "416-22 II 50203... a.s.o"

---

Now also looking in to the circuit board of the ECU, following the pins above, in on the PCB, and goint to 4 pins on an IC circuit called "VN450" (SOP-20 capsule).
Searching and finding the datasheets for this circuit, it tells it is a "smart" circuit, with lots of overcurrent protection (!).
Seems age anyway got to it.

Finding the input of the IC for the Right brake light, testing it by braking, it going high, it still did not run the output side for the Right brake light.
But, the input for the left side brake light, worked running the output of the left brake light.

Looking in the datasheet of VN450 at the current the brake light bulb draws it is around 4Amps. And the circuit, who runs brake lights on both sides with 2 individual outputs of 4 pins, where of each should be capable of 8 Amps.

Thinking "hmmm"...

---

I of course ordered a set of VN450 IC's.
They are "obsolete" and not produced any more, at least not in this configuration.
But, the IC can be found on the market. Different companys/sellers hoover the market for obsolete IC's, making a fair profit selling it later.

I found a set on eBay. $4.69 ea + $3 shipping. Nice price.
Reason I bought more than I needed, was to be prepared for som failure, or frying the IC when soldering or disassembling.

Also ordered a 2nd ECU, WITH 2nd row text under the HW part no, that said "416-22 II 50203... a.s.o"
(Ordered it. Polish seller did not answer. Did not sell to Sweden. Found in Ukraine(!). More expensive. Turned out later that Ukrainean company bought from same seller Poland, and got Poland to ship to Sweden).
Of course, if I could get a unit and just replace, it would be better than having the work with fixing my original J393 ECU.

---

Finding the parts and the ordering processes took time,
so I needed a solution not wanting to get stopped by police, and banned from driving my Touareg.

Going back to the IC output of 8 Amps capability of each side, and only measuring using 4A, I made a temporary fix on my original ECU.
I thought it could work for a while at least, and if not, it will only fry the left side also on the already fried right side IC, that anyway was to be replaced.

So, I shorted the left output to the right non working output.
Voila!
Now, with this temporary fix, it worked again.

---

 

[ChriberV8]

Finally receiving the 2nd disassembled J393 ECU, with the 2nd row having the same text as my original ECU (from a Porsche Cayenne), I tested it.

Trunk soft close worked!

But, a few seconds of not being able to unlock, until I realized instead of using 2 buttons on the remote for Lock/unlock on VW, the Porshe used only 1. The same button.
And 1 press unlocked driver door, 2 fast presses unlocked all doors. (J393 Comfort ECU holds more functionalities than back lights).
So seems there still were a lot of variant programming also on the ECU's.

Not having any instrument or equipment reprogramming variants, I went in to the cluster, some variants can be changed in the menu for the locking.
This was interesting.
The text in the menu became larger, and then it locked. The cluster menu locked.

I noticed also the air suspension, had a slightly different ride cornering.

Realizing I needed to fix my original ECU, it anyway worked until I got the VN450 IC's.

After arrival, I got to it,
I did not have any hot air soldering equipment, so needed a method for getting the old IC out.

First,
I filled all legs, on both sides of the IC, with more solder,
to use 2 solder irons, one on each side, to when hot enough, pick it up or move it, like with a tweezer.

Now,
this did Not work.
After some time heating it, I realized it also had a soldered bottom/belly, to the PCB.
You can see the short side of the IC having tin/solder underneath it, to the PCB kopper in the picture.

So how do I solve this?

Second method,
First heating and sucking away all the solder I put over the pins.
Then a razor, or very sharp knife, dragging it along the long side of the IC, over the legs coming out of the capsult.
Gently, and not too hard.
4-5 times, like with a carpenter pen.

Then, I with the razor/knife push the 1st leg in the line, gently, until a small quiet snap.
1st leg was cut from the IC capsule body.
Then next leg, a.s.o.
1st row done, now second row/line.

Bend the cuts legs still soldered to the PCB away, (gently and just a notch not to hurt the pcb copper the legs stand on), away from the capsule.
Add some solder to the short sides. will take som heating since dissipating >50W normally.

When some solder on, take the 2 soldering irons, and pinch the IC on both short sides (I used approx 400C setting).
When IC start move or being lose, just take it away.

Then solder each and every leg from the IC off.

BE CAREFUL!

The Very Small resistor components below the accident site in the picture, by heat easily moves away or get burned.

And by experience, even though having special optics with huge magnification, run away components are Not easy to refit without proper tools.
Also risk of damaging the copper isles components are to be soldered too.

Putting the new VN450 back is done by cleaning the PCB isles, pre add a tiny notch of solder.
The same for the area under the IC, which need to be soldered to dissipate the heat of the IC, but do not build any hight at all of solder. Just new surface skin.
If building higher, having increased hight of the capsule, it will then become harder to solder the IC legs to their isles/pads on PCB.
Also keep in mind to have the same orientation of the IC when putting the new one back.
Note the phased corner!

So, if anyone experiences a Non working brake light on One side, whilst the same side red running light and indicator works,
Here You have One possible error cause, and fix.

Now it works Perfect!

 

[ChriberV8]

Oh,
Almost forgot!

In the latter pictures, when replacing the IC,

You can see I have removed the Fix solution short, that I made on the connector earlier!

 

[ChriberV8]

 

[C-ya]

Good thinking to get it working.

 

[ChriberV8]

Thanks!

I had to fix it.
Just love my 2003 Touareg V8.
(Everything is good except the fuel consumtion in high... any speed )

Good thinking to get it working.

 

[TommiT]

Golly, that was way too complicated just to fix a brake light!! Well done for persevering.

 

[ChriberV8]

Yes.
First time is always tricky, and long leadtime with the orders.
Hopefully the post can help someone else.

Now, when knowing all, it would not take more than a 4 hours.
And this because of the interior down and up again.