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Looking for factory manual wiring schematic for rear lights

8K views 44 replies 7 participants last post by  mstrjon32 
#1 ·
Hoping someone has a Sky factory manual and can send me the schematic for the rear lights. I have the OEM manual for the Solstice but of course those cars only have a single bulb in the rear, and I need to know how they are wired from the BCM on the Sky. Trying to see if there's a nice way to fit the Opel GT lights and have the turn signal flash as appropriate without changing any wiring, basically flashing in the Opel GT BCM software or something.

Thanks in advance,
 
#2 · (Edited)
This sounds wrong as I write it: Are you attempting to install Opel tail light assemblies into a Solstice? If so, wiring is the least of your worries, as the body shapes are completely different.

I can post the actual diagrams later, but for now all you get (from me) is words. I also have no hands-on experience with the Opel lights, but someone else may be able to add the missing insight.

The "magic" of the Opel tal lights is in the wiring harnesses, and not the BCM, as far as I can tell.

The 2008 wiring diagrams for the Sky and Solstice appear to be identical from the BCM to two connectors at the back of the car.
The 2006 Solstice and 2007 Sky diagrams also agree, at least to the limit that I compared them.
  • X400 (IP Harness to Rear Lamp Harness) has four pins
    • BK Ground
    • BN Tail / License / Park
    • L-GN Backup
    • L-BU Stop
  • X408 (Chassis Harness to IP Body Harness) has eight pins
    • BK Ground
    • TN Left Wheel Speed
    • OG Low Ref
    • BN Right Wheel Speed
    • WH Low Ref
    • YE Left Stop / Turn
    • BN Tail
    • D-GN Right Stop / Turn
From these connectors the wiring is unique to each model, interconnecting between the connectors and the light assemblies.

I have no specific documentation for the Opel, and have never heard that any exists..
 
#3 ·
Thanks, sorry if it wasn't clear. I have the service book for the 2007 Solstice, but I'm trying to put the Opel lights in my Sky. Years ago I ordered the service book for the Sky from the US and they sent me the Solstice book, and it was such a pain to send it back and try to exchange it I never bothered, figuring they were similar enough for my needs.

The schematics from the Solstice book show a double filament bulb with a single wire on C308/18/YE (stop/turn) for the high-intensity side of the bulb on the left side. Meaning that, it seems as if there is no way to fire the signal vs. the stop lamp separately [assuming the Sky is the same]. If you're saying in the schematic for the 2008 that it's the same for both cars, then I'm guessing on the Sky that one circuit is wired to both bulbs in the assembly.

As the Opel has one bulb for the signal/hazard and one for the stop lamp, it seems to me as if they would have run two circuits and reprogrammed the BCM to fire the the turn lamp and the stop lamp individually. But, it sounds like I might need to see the Opel book to know for sure.

If there aren't two circuits in the Sky and reprogramming isn't possible, then the next most straightforward solution seems to be to wire the high-intensity outputs of the left and right lamps to the center lamp circuit with a relay, and then to just run another wire to the rear lights for the signal bulbs and jumper them from the front indicator circuits. (Will there be a fast-blink then because the rear bulb will be "missing?" Ugh. I guess I need to think about it. Hopefully there are two circuits and software reprogramming will be possible.)

Or, better yet, if someone else has already done this and can tell me the easiest way to do it, I'm happy to hear it. 😁
 
#4 ·
What are the differences in operation between the two (Sky vs Opel)?

When I installed the rear Opel lights onto my ‘07 Sky, I didn’t even think to worry about schematics, wiring differences and any changes that might occur. Didn’t even realize (apart from bulb difference because of the connector) that there was a difference.

Thought they were both interchangeable.
 
#5 ·
That makes a lot more sense than what I was thinking, and I couldn't remember what you have. I regret not being able to post the diagram yet, but the value it will have is questionable at best.

@marlboromike has done this conversion, and has mentioned the unique harness needed, so i am hoping that he can add some actual knowledge.

Meanwhile i will speculate.

The connector for the sub-harness built into each tail light assembly has six pins, only three of which are used in the Sky: Ground, Tail, and Stop / Turn. You are correct that the two bulbs are jumpered by that harness. Significantly in my mind, the Stop / Turn wires to each bulb are different colors in that sub-harness, suggesting that they are separate circuits for the Opel. If you have the light assemblies you can confirm that. Are there four pins used in the connector?

Assuming they are split, it would be relatively simple to get a non-blinking Stop lamp by adding a wire from the CHMSL pin in X400 to one of the circuits in each tail light. You may then need a load resistor, like those used with LEDs, to eliminate the hyper-flash.
 
#6 ·
Thanks for the input. Let's see what @marlboromike has to say about it then. If he actually has the signals working as intended and knows the parts I need, then I'll owe him a beer for sure.

For me this is about road legal compliance, not about the aesthetic of it, so I really need the indicator to flash yellow as intended. I actually prefer the look of the Sky lights.
 
#8 · (Edited)
Mike, where I live the Sky lights are the illegal ones. This is the only reason I have to switch them. 😁

I found some of the threads you are referring to, but it seems like the solution is the blunt option of just wiring the rear lights to the front ones, using the center light to trigger the brake lights, and putting in a resistor. I was hoping that there was some knowledge of how the Opel itself actually was delivered and if it could be "correctly" retrofit.

I can't believe that anyone would go through this pain just for the look of the lights. It's almost as mental as putting on those gigantic mirrors. 😁😉
 
#11 ·
Those are the lights--the issue is that I need them to function exactly like on the Opel. Indicators flashing as appropriate and a solid red light when braking.

It seems like it's doable to wire the indicators to the front lamp circuit, use a relay to fire the brake lights from the center lamp, and use a resistor to keep the fast flash from happening, but I was really hoping there was a solution that was more factory "plug-and-play," as it were.
 
#13 ·
I have been thinking about this since you first posted, and i have a couple of new thoughts.

As you have found, the wiring done to use the Opel lights in the US isn't going to work for you.

I think, with the correct harness, you could get the wiring to be totally factory. The lower-half red light would be connected (through that harness) direct to the CHMSL connector for a solid light when braking, and the upper-half clear/amber would be connected to the existing stop / turn wiring for a flashing light when turning. The problem is that you would also have a solid amber when braking. At that point there is likely a different BCM program that is used for the Opel that would eliminate the amber light when braking.

You can accomplish the wiring by running a single wire from the L-BU (Stop) wire at X400 to the fourth pin on each of the Opel tail light connectors. I am guessing that is the correct pin for the brake lights, but you may have to switch some pins around. No relay is needed because you aren't trying to isolate anything. This would also be a good opportunity to switch the bulbs to LEDs, since the rake lights do not have current sensing issues.

As an alternative to trying to find a different program, with all of the problems that could cause, I would get into the wiring at the BCM. The front turn signals feed from (I think) X1, and the rears from (I think) X3. You can cut the rear signal wires and then splice them into the fronts. Depending on the wattage of the Opel turn signal bulb, you may or may not get hyper-flash. If you do, you can use the rear connections from X3 for the resistors. You just have to find a place to mount them so that their heat won't damage anything.
 
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#12 ·
Did your lights come with the electrical attachments to plug in light bulbs?

Also, what do you think is different in braking/lightning patterns between the Sky and Opel?

This could’ve been misinformation or confusion but when I bought my Opel lights, way back in ‘10, I was told that the Sky and Opel rear lightning patterns were the same (braking, turn signal, etc).

Like I said earlier, I’m confused because I just removed my original Sky lights, plugged the Opel lights in, and went on my merry way. Help me guys… what am I missing here?
 
#14 ·
I really do not understand the problem here...do not touch anything up front....no resistors....my Opel tail light...u put on the brake, both the amber and red light up....when u put your headlights on, the red go on. When u turn...the red light only. All it was was cutting one wire (cannot remember which) and vampired it to another.
 
#15 ·
Mike, that was fine for you, but won't work for mastrjon32. He is trying to set the lights up to comply with the European spec. The amber (only) has to be the turn signal and the red (only) has to be the tail / stop signal.
 
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#16 ·
The AMBER light should only turn on when signaling turns, should NOT turn on when brake is applied.
Its been a long time I seen a schematic for these lights (my days of sequential turn signal) but I believe it’s a solid green wire in the tail light harness that controls the turning signal and that’s the one with its black ground that should go to your Amber light.
 
#17 ·
The AMBER light should only turn on when signaling turns, should NOT turn on when brake is applied...........
Exactly. The problem is that the Sky does not have an existing wire at the rear of the car that is turn signal only.

The options that i can see are: 1) Reprogram the BCM, 2) Build a circuit that monitors both stop/turn wires and prevents them from both being on simultaneously, and 3) Splice the rear turns into the front turns at the BCM.
 
#19 ·
The real question here is--why didn't they just use the Opel style lamps for the US market? I know that some cars in the US come with yellow indicators. Seems like it's more effort, and thus less cost effective, to make two separate styles.

(Though in my opinion the Sky lamps do look better!)
 
#21 ·
The real question here is--why didn't they just use the Opel style lamps for the US market?
(Though in my opinion the Sky lamps do look better!)
I owned both these type of tail lights and must say the original Saturn Sky tails are made a hell of a lot better. To me the Open tail light look and feel cheap, BTW I believe Opel only carrys single filament bulbs in them..
 
#23 ·
I did some poking around and was able to find the Opel GT part numbers. I'm not going to ask how they got all of the information, but you can see basically the entire Opel parts catalog here: ilcats.ru.

It looks like the harness for the rear lights for the 2007 chassis is part number 25825866, however I don't see it for sale anywhere on the web. The listed replacement part number for the 2008 chassis, 25886917, I do see for sale. However, I suspect that it would need to plug into the main Opel BCM harness, which also seems to be for sale for the 2008 chassis, but looks like it's more than 500€, and would require ripping the entire car apart to install "correctly," and I'm almost certain I can't be bothered. If I can figure out the part number for the Sky main harness, and by some crazy chance they're the same part, which I hugely doubt, then maybe it's worth buying the Opel lamps harness and just connecting it to see what happens.

I still need to see if I can flash the Opel software onto the BCM or if that will be a fight. I used the Tech2 to set the Sky BCM software settings, but there wasn't much to adjust (unlike my Saab, which has endless settings), just a setting for "USA," "Canada," or "Export" and some installed feature choices. I set it to "Export," but the brake lights are still working the way I'd expect them to, which suggests that it isn't switching the circuit over to signaling only with that selection. In fact, I have no idea what that is doing...I will try to get the Opel SPS software working but it is always a struggle.

We'll see how far I actually go with this--I'm only doing this so I can sell the car locally. So far it's been a real struggle to find a buyer who wants to deal with this bullshit (I don't blame them) despite my low asking price. In a strange turn of fate, all this fiddling with the car has had me driving it more recently, and making me less inclined to sell it. Oddly enough, if we do keep it and bring it with us when we move, New Zealand does allow red turn signals, so I won't have to do this anyway (though they have plenty of their own import hurdles that I'm really not feeling like dealing with.) Or we'll never move, so far I've been saying we're moving for two years and we're still here.
 
#24 ·
FWIW, the harness for the rear fog lamp/reversing lamp is listed as 25890034, though it looks from the photos like it also connects to the main BCM harness. The ticket will be determining if the Sky and the Opel use the same main BCM harness. If they do, then it might be possible to do a factory-original conversion with a software re-flash and only a minimal headache.

I don't have access to a Sky parts catalog--if anyone has the information for that part number, that would be helpful.
 
#25 ·
Did a little more digging and determined that the main harness depends on if the car was equipped with the Monsoon system or not, and is different for each year. Also found (on the German GT forum, actually) part information for the Sky. That information only shows 15861147 as the part number with a note saying "order by application," but doesn't show any more information. So, I guess this doesn't really get me any closer to the answer.
 
#27 ·
The harnesses won't be the same, since the Opel harness will at a minimum need the additional wire for the rear fog light. Whether that is the only difference is the real question.

Helm has a link for requesting a manual that they do not have, so i sent an email asking about documentation for the M-Platform Opel.

BCM input/output assignments is the crucial information, since that will tell you if there are different outputs for the Opel than for the Sky.

I read the requirement for the rear fog light and it stated that some jurisdictions require a single light to be offset to the driver's side. The Opel rear fog was integrated into the backup lamp in the center of the car. Is location an issue for you? Can the rear fog light be operated with the front fog lights, or does it have to be independent?
 
#29 ·
The harnesses won't be the same, since the Opel harness will at a minimum need the additional wire for the rear fog light. Whether that is the only difference is the real question.
My thinking is that there is a [small] chance that the main harness is the same, and the harness the connects the lights to the main harness is where the difference lies. Based on the parts diagrams on that Russian website, 25886917 is a different part that looks like it connects to the main harness. If the only difference is in that rear harness, then I might be able to more easily switch that and get a "perfect" conversion.

Helm has a link for requesting a manual that they do not have, so i sent an email asking about documentation for the M-Platform Opel.
🍻

I read the requirement for the rear fog light and it stated that some jurisdictions require a single light to be offset to the driver's side. The Opel rear fog was integrated into the backup lamp in the center of the car. Is location an issue for you? Can the rear fog light be operated with the front fog lights, or does it have to be independent?
Depends, if it gets sold locally and goes to TÜV Rheinland for a vollabnahme and issuance of compliance papers, I know the center light is OK as that's what they approved for use on the Opel GT in Germany. I suspect they're going to scrutinize everything else to the maximum extent possible, however.

If we bring it with us to New Zealand, there's going to be a lot more uncertainty on that. What I'm much more worried about with an NZ import would be the headlight beams being too high on the right side--as that's a much harder situation to correct, though I think because the projectors produce a flat beam it "should" be acceptable.
 
#32 ·
It shouldn't be any surprise that Helm wasn't any help.

Their website has this note:

Can’t find it? We’ll find it for you! Send us an email or call (800) 782-4356 with your questions and we’ll contact the manufacturer directly!

I sent an email asking for documentation on the differences between domestic and export M-Platform cars at 10AM, and received this reply at 7PM:

We search by year make and model and do have some manual sets available for purchase. 2007 & older is aren't so takes longer since printed on order basis do not have on hand and it may bot have all the wiring diagrams in it.

But no i would not be able to provide you any information on your vehicle just manuals available here with Helm.

The time lag didn't seem sufficient for messages to and from GM, and the reply does not indicate that they did anything other than check their catalog.
I suggested that they remove the offer to contact the manufacturer from their website, since it doesn't seem that they actually do it.
 
#36 ·
So I was able to get a peek at the Opel schematics today. Bottom line is that if I can get the BCM reflashed with the Opel software, the existing wiring in the Sky for the tail lights should support flashing the indicators only. Looking at the diagram for the Opel under hood fuse box, it looks like they added a tail light relay and fuse and a rear fog light relay and fuse, so I can only assume that it's not safe to run all the lamps off of the BCM supply without a relay, and I need to try to get more information to work out if there are any other changes that will make me regret putting the Opel software on the Sky BCM.

Then we have the issue of can I even load the Opel software on there. Looking at the SPS info pages for my Sky VIN, it doesn't show a specific program for the BCM, it shows an ECM program that might be comprehensive, but it's hard to tell without actually paying the 35€ for the two hours of SPS access and I'm not sure I'm ready to try it yet. I don't actually have the parts yet so if it does work I'm going to turn the existing red lamps into indicators only, which is not ideal.
 
#37 ·
A little bit more research on the web suggests that the Sky BCM and the GT BCM are the same part number--still not sure about the programming, or if it can even be flashed using SPS at all. Which leaves me with the question of, if they are both using the same software (and I've already tried setting mine to "Export") what needs to be done to get it to use the Opel programming? Is it reading the model information from the ECU and then deciding how to behave?
 
#40 ·
I'm still at a bit of a loss regarding how to flash the BCM with the Opel software, or even if there is Opel specific software at all. Obviously somehow the Opel's are configured to operate differently, and it appears that the part number crosses over with at least a few other cars (Chevy Cobalt, HHR, etc.), so there must be a way to set up the hardware for each car. I did see at least one article suggesting that there was some BCM update way back in 2006 or something that could be programmed, but I just don't see any reference to BCM software for this car on the tis2web external page, and I wouldn't expect it to be any different once I pay for access, as it's generally consistent.

I've seen some things suggesting that you need to set the RPO codes as the first step when configuring the BCM, but when I connected my Tech2 to it last week, that was not presented as an option when configuring the BCM. But, as I write this, it does occur to me that some of the processes with the Tech2 are pretty inconsistent, so perhaps I need to "remove" and "add" the BCM again to be able to customize the RPO codes?

More tinkering is in order, hopefully I don't brick the BCM and put myself out another 200€. If this gets to me well enough I'm going to pull the BCM out of the car, find a flash reader and harness, and disassemble the damn software.
 
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