Originals rear lights won't code in

[JDM82]

I've removed my led rear lights and fitted the original lights. The retrofit guy coded the car to accept the standard lights but the warning dash light comes on and the rear lights are very dim.

The guy is looking into it but I thought I'd ask with the hope someone has had the same issue and can point me in the right direction.

Any help much appreciated

[golfhappy]

Try byte 19 in CECM don't know what your's is set to but could be 88 of 86. From memory think it's the second number this either increases or decreases the voltage to the tails.

[jb0o]

Hi guys,

Thought I'd put my input in here as I'm the retrofit guy mentioned above.

This is a very interesting situation as its confusing the hell out of me.

Every retrofit I do, I always take a full scan of the vehicle, so in case anything goes wrong, I have a full coding snapshot of what the car was like before, so I can always revert.

The OP came to me a while back to fit the LED Rear lights - everything was fine and it was a simply retrofit, however when coming to revert these back to the original, it wasn't as simple. I used the original coding from the first time we'd met and assumed that would put everything back to factory, but there are still two errors that exist:

Code: [Select]

2 Faults Found:
00984 - Left Tail Light (M4)
            007 - Short to Ground
             Freeze Frame:
                    Fault Status: 01100111
                    Fault Priority: 2
                    Fault Frequency: 1
                    Reset counter: 67
                    Mileage: 49793 km
                    Time Indication: 0
                    Date: 2015.03.14
                    Time: 17:06:58

             Freeze Frame:
                        Term 15 On
                    Voltage: 13.75 V
                        ON
                        ON
                        Term 50 Off
                        OFF
                        OFF

00985 - Right Tail Light (M2)
            007 - Short to Ground
             Freeze Frame:
                    Fault Status: 01100111
                    Fault Priority: 2
                    Fault Frequency: 1
                    Reset counter: 67
                    Mileage: 49793 km
                    Time Indication: 0
                    Date: 2015.03.14
                    Time: 17:06:58

             Freeze Frame:
                        Term 15 On
                    Voltage: 13.75 V
                        ON
                        ON
                        Term 50 Off
                        OFF
                        OFF
I'm going to chat to a few guys over the week and see if they can think of anything, but currently his coding is exactly how it was when we first met, so I can't understand how the above issues are occurring..

Thanks,
Jonny

[golfhappy]

Looks like a wiring fault...short to ground! Especialy when you say the tails are not of the correct brightness. Bad earth?

[mavs]

I feel your pain mate. Struggled like hell getting mine to code up correctly. I know you mentioned you ran a full scan at the start, but byte 18 is usually coded in as 00 which isn't actually the original factory code, it is hiding the actual code. Have you tried changing byte 18 to (15). This is how I got my original (non led) tails to run correctly with bi xenon headlights. I'm now running 04 with led tails and bi xenons and all is running fine. 03 has also been proven to run halogen and non led tails fine on American gtis. May well be worth a shot?

[jb0o]

Looks like a wiring fault...short to ground! Especialy when you say the tails are not of the correct brightness. Bad earth?

Yeah, you'd think that by the fault however I believe this is being caused because the coding seems to believe it still has LED's and is therefore only sending a certain amount of voltage to the rear lights (as LED's require much less voltage what standard filament bulbs).

I feel your pain mate. Struggled like hell getting mine to code up correctly. I know you mentioned you ran a full scan at the start, but byte 18 is usually coded in as 00 which isn't actually the original factory code, it is hiding the actual code. Have you tried changing byte 18 to (15). This is how I got my original (non led) tails to run correctly with bi xenon headlights. I'm now running 04 with led tails and bi xenons and all is running fine. 03 has also been proven to run halogen and non led tails fine on American gtis. May well be worth a shot?

Its interesting you mention that about the 00 with Byte 18, as VCDS gives the impression that it is hidden as the 00 showed no value in the dropdown selector.

It could be true that even after coding the lights in Byte 18, the coding resets itself, even though the coding has a different set value. This could be similar to the way login codes work. Thanks for the info on value 15/03- they'll be definitely worth a shot, although I'm certainly I tried value 15 previously, but I'm not sure on 03.

I also found an interested thread on this issue over at: http://www.golfgtiforum.co.uk/index.php?topic=192588.0, which seems to be the exact issue we're seeing - so I'll have a good read over that thread for when we try fix this next weekend.