# Need wiring diagram 99' Pontiac Grand Prix SE trunk light **URL:** \ **Category:** Maintenance/Repairs\ **Created:** [March 5, 2023, 7:27pm UTC](https://community.cartalk.com/t/need-wiring-diagram-99-pontiac-grand-prix-se-trunk-light/189449 "2023-03-05T19:27:57Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![old\_mopar\_guy](https://avatars.discourse-cdn.com/v4/letter/o/6bbea6/32.png) [@old\_mopar\_guy](https://community.cartalk.com/u/old_mopar_guy)\ **Post date:** [March 6, 2023, 2:51pm UTC](https://community.cartalk.com/t/need-wiring-diagram-99-pontiac-grand-prix-se-trunk-light/189449/21 "2023-03-06T14:51:50Z")
Mr. Volvo said it better than i could. ---
**Author:** ![eddo](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/eddo/32/2594_2.png) [@eddo](https://community.cartalk.com/u/eddo)\ **Post date:** [March 6, 2023, 3:52pm UTC](https://community.cartalk.com/t/need-wiring-diagram-99-pontiac-grand-prix-se-trunk-light/189449/22 "2023-03-06T15:52:03Z")
@realrobd Are you sure the trunk light is working as it should? Why would it be designed to come on only when the interior lights are on? That doesn’t make sense to me. Personally, If this is what I was after, I’d run a new wire from the fuse box to a mercury light switch in the truck- or even a manual switch so I could make sure it was off when it was supposed to be off. Fuse the wire and enjoy. ---
**Author:** ![bing](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/bing/32/4619_2.png) [@bing](https://community.cartalk.com/u/bing)\ **Post date:** [March 6, 2023, 5:24pm UTC](https://community.cartalk.com/t/need-wiring-diagram-99-pontiac-grand-prix-se-trunk-light/189449/23 "2023-03-06T17:24:31Z")
Thinking about this, it makes no sense at all. Everything goes back to the bcm and controlled by one fuse. So you have to turn the dome light on or have the doors open for the trunk light to work?the library should have a manual with the diagram but as said unless it is helms, can’t rely on it. ---
**Author:** ![capricornfencing](https://avatars.discourse-cdn.com/v4/letter/c/a88e57/32.png) [@capricornfencing](https://community.cartalk.com/u/capricornfencing)\ **Post date:** [March 6, 2023, 6:51pm UTC](https://community.cartalk.com/t/need-wiring-diagram-99-pontiac-grand-prix-se-trunk-light/189449/24 "2023-03-06T18:51:36Z")
The first thing you’ll need to do is locate the wiring diagram for your vehicle. You can find this in the owner’s manual or you can search online for a copy. Once you have the wiring diagram, you’ll be able to identify the switch that controls the trunk light. Once you’ve identified the switch, you’ll need to trace the wiring from the switch to the trunk light. This will help you determine how the switch is wired and how it is connected to the trunk light. Once you have this information, you’ll be able to rewire the switch so that the trunk light will illuminate when the trunk is opened or closed. If you’re not comfortable with rewiring the switch, you can always take your vehicle to a qualified mechanic or auto electrician. They will be able to help you rewire the switch and get your trunk light working properly. I hope this information helps you out. Good luck with your project! ---
**Author:** ![Nevada\_545](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/nevada_545/32/41232_2.png) [@Nevada\_545](https://community.cartalk.com/u/Nevada_545)\ **Post date:** [March 6, 2023, 7:00pm UTC](https://community.cartalk.com/t/need-wiring-diagram-99-pontiac-grand-prix-se-trunk-light/189449/25 "2023-03-06T19:00:49Z")
> [@capricornfencing](#): > > Once you have this information, you’ll be able to rewire the switch so that the trunk light will illuminate when the trunk is opened or closed. The trunk switch provides the ground for the trunk light, no need to rewire the switch. The body computer supplies the power to the trunk lamp. ---
**Author:** ![George\_San\_Jose1](https://avatars.discourse-cdn.com/v4/letter/g/e5b9ba/32.png) [@George\_San\_Jose1](https://community.cartalk.com/u/George_San_Jose1)\ **Post date:** [March 6, 2023, 9:12pm UTC](https://community.cartalk.com/t/need-wiring-diagram-99-pontiac-grand-prix-se-trunk-light/189449/26 "2023-03-06T21:12:16Z")
> [@old\_mopar\_guy](#): > > Just get the helm schematic, The only factory service info I see there for a 99 Grand Prix is an emissions system diagnostic manual. $50. Do you think it would have the wiring diagram the OP needs? > [@Nevada\_545](#): > > The trunk switch provides the ground for the trunk light, no need to rewire the switch. The body computer supplies the power to the trunk lamp. The OP wants the trunk light to turn on whenever they open the trunk, which would require BCM to supply power to that ~~switch~~ circuit at all times. > [@capricornfencing](#): > > locate the wiring diagram for your vehicle. You can find this in the owner’s manual or you can search online for a copy. Unlikely to be in an owner’s manual. The needed diagram is probably posted on-line somewhere, but may take a good deal of searching to find it. > [@Tester](#): > > Don’t trust a Haynes or a Chiltons for wiring diagrams… They’re not accurate. Even a factory service manual can contain incorrect information. ---
**Author:** ![Tester](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/tester/32/15976_2.png) [@Tester](https://community.cartalk.com/u/Tester)\ **Post date:** [March 6, 2023, 9:15pm UTC](https://community.cartalk.com/t/need-wiring-diagram-99-pontiac-grand-prix-se-trunk-light/189449/27 "2023-03-06T21:15:51Z")
> [@George\_San\_Jose1](#): > > Even a factory service manual can contain incorrect information That’s very rare. But very common with Haynes/Chilton’s. Tester ---
**Author:** ![Nevada\_545](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/nevada_545/32/41232_2.png) [@Nevada\_545](https://community.cartalk.com/u/Nevada_545)\ **Post date:** [March 6, 2023, 9:19pm UTC](https://community.cartalk.com/t/need-wiring-diagram-99-pontiac-grand-prix-se-trunk-light/189449/28 "2023-03-06T21:19:06Z")
> [@George\_San\_Jose1](#): > > The OP wants the trunk light to turn on whenever they open the trunk, which would require BCM to supply power to that switch at all times. The trunk switch is like a door ajar switch, it only has a ground connection, no place for a power feed. Basic diagram below; ![image](https://global.discourse-cdn.com/cartalk/original/3X/4/3/4339d36ddd8b5d5bc685180b953524e0e0db77ff.png) ---
**Author:** ![bing](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/bing/32/4619_2.png) [@bing](https://community.cartalk.com/u/bing)\ **Post date:** [March 6, 2023, 9:27pm UTC](https://community.cartalk.com/t/need-wiring-diagram-99-pontiac-grand-prix-se-trunk-light/189449/29 "2023-03-06T21:27:56Z")
I guess other pontiacs may be different but I have a hot power wire going to mine. Ground is on the metal body to complete the circuit. Made me look in my trunk but I’m done with this one now. I’m just not convinced of the original symptoms. I’m late for my last class on the federalist paper though so gotta go. Everyone is free to do what they want ---
**Author:** ![George\_San\_Jose1](https://avatars.discourse-cdn.com/v4/letter/g/e5b9ba/32.png) [@George\_San\_Jose1](https://community.cartalk.com/u/George_San_Jose1)\ **Post date:** [March 6, 2023, 9:39pm UTC](https://community.cartalk.com/t/need-wiring-diagram-99-pontiac-grand-prix-se-trunk-light/189449/30 "2023-03-06T21:39:51Z")
> [@Nevada\_545](#): > > Basic diagram below; I’m unsure of your point. The diagram you’ve shown is exactly the functionality the OP wants, trunk light turns on whenever trunk opened. Are you saying b/c the + voltage isn’t sourced directly by the battery in OP’s car , but from the BCM, the OP cannot obtain the desired functionality? > [@Tester](#): > > very rare . > > But very common with Haynes/Chilton’s. No dispute, agrees with my experience as well, especially for wiring info. But for something like a trunk light wiring diagram, what would you recommend if not Haynes/Chilton? OP attempt to locate & purchase the factory service manual? OP attempt to locate the diagram on-line? OP hire a shop to rewire the light the way they want it? ---
**Author:** ![Nevada\_545](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/nevada_545/32/41232_2.png) [@Nevada\_545](https://community.cartalk.com/u/Nevada_545)\ **Post date:** [March 6, 2023, 9:43pm UTC](https://community.cartalk.com/t/need-wiring-diagram-99-pontiac-grand-prix-se-trunk-light/189449/31 "2023-03-06T21:43:07Z")
> [@George\_San\_Jose1](#): > > I’m unsure of your point. > [@George\_San\_Jose1](#): > > which would require BCM to supply power to that switch at all times. You do not apply power to the trunk switch, that switch is a ground only. ---
**Author:** ![Tester](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/tester/32/15976_2.png) [@Tester](https://community.cartalk.com/u/Tester)\ **Post date:** [March 6, 2023, 9:45pm UTC](https://community.cartalk.com/t/need-wiring-diagram-99-pontiac-grand-prix-se-trunk-light/189449/32 "2023-03-06T21:45:01Z")
> **[Do it Yourself Automobile Repair Manuals - Mitchell 1 DIY](https://www.eautorepair.net/Marketing/default.asp?VID=&Count=Y)** > > Mitchell 1 DIY, Provides Professional Repair, Estimator, Maintenance, TSB and Recall information for Automotive enthusiasts. Tester ---
**Author:** ![George\_San\_Jose1](https://avatars.discourse-cdn.com/v4/letter/g/e5b9ba/32.png) [@George\_San\_Jose1](https://community.cartalk.com/u/George_San_Jose1)\ **Post date:** [March 6, 2023, 9:51pm UTC](https://community.cartalk.com/t/need-wiring-diagram-99-pontiac-grand-prix-se-trunk-light/189449/33 "2023-03-06T21:51:44Z")
> [@Nevada\_545](#): > > You do not apply power to the trunk switch, that switch is a ground only. Ok , I should have said “circuit” rather than “switch”. Will correct above. Is it possible for OP to obtain the functionality they want? ---
**Author:** ![Nevada\_545](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/nevada_545/32/41232_2.png) [@Nevada\_545](https://community.cartalk.com/u/Nevada_545)\ **Post date:** [March 6, 2023, 10:34pm UTC](https://community.cartalk.com/t/need-wiring-diagram-99-pontiac-grand-prix-se-trunk-light/189449/34 "2023-03-06T22:34:32Z")
I think anyone can wire up a lamp as long as they don’t create a short to ground. 10 minutes after exiting the vehicle the BCM disables all courtesy lights to prevent a battery discharge, that is why there is no power to the trunk lamp when returning to the vehicle. Should the trunk ajar switch wake up the BCM? I don’t know, I would just use the keyless entry remote to unlock the doors and thereby switching on the courtesy lights. ---
**Author:** ![George\_San\_Jose1](https://avatars.discourse-cdn.com/v4/letter/g/e5b9ba/32.png) [@George\_San\_Jose1](https://community.cartalk.com/u/George_San_Jose1)\ **Post date:** [March 6, 2023, 10:49pm UTC](https://community.cartalk.com/t/need-wiring-diagram-99-pontiac-grand-prix-se-trunk-light/189449/35 "2023-03-06T22:49:18Z")
Re: Mitchell’s online manuals My only Mitchell’s repair manual experience is with their prior big books. Many years ago I installed new clutches on my truck’s rear limited-slip differential using a Ford 9-incher Mitchell chapter for reference, as I recall. I found it to be generally pretty good, comprehensive info, but like All-Data, geared to mechanics. They assumed the reader had quite a bit of experience doing car repairs and car-repair nomenclature. Besides Mitchells I seem to recall another vendor who published similar auto-repair info in big books, maybe started with the letter “C”, but forget its name. The Mitchell’s online price seems pretty reasonable. $20 for a month, $40 for an entire year, $60, four years. imo OP should definitely consider this option to obtain the needed wiring diagrams. > [@Nevada\_545](#): > > I would just use the keyless entry remote to unlock the doors and thereby switching on the courtesy lights. OP, is there a reason this method wouldn’t accomplish what you want? ---
**Author:** ![realrobd](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/realrobd/32/34389_2.png) [@realrobd](https://community.cartalk.com/u/realrobd)\ **Post date:** [March 7, 2023, 2:49pm UTC](https://community.cartalk.com/t/need-wiring-diagram-99-pontiac-grand-prix-se-trunk-light/189449/36 "2023-03-07T14:49:13Z")
Lights do not come on when unlocking with the fob. Only when opening the door. ---
**Author:** ![George\_San\_Jose1](https://avatars.discourse-cdn.com/v4/letter/g/e5b9ba/32.png) [@George\_San\_Jose1](https://community.cartalk.com/u/George_San_Jose1)\ **Post date:** [March 7, 2023, 9:40pm UTC](https://community.cartalk.com/t/need-wiring-diagram-99-pontiac-grand-prix-se-trunk-light/189449/37 "2023-03-07T21:40:43Z")
It appears @Nevada_545 's suggestion won’t work. Back to the drawing board I guess. OP, have you decided yet how you’ll obtain the pertinent wiring diagram? Or are you just going to wing it; i.e. use whatever diagrams you can find on Google, etc? Tester’s post above that Chilton’s Haynes wiring diagrams can be inaccurate is true from my experience, but the primary reason imo is that those manuals cover a bevy of models and model-years. So while a particular wiring diagram they show for a function (like the trunk light) may well be an exact copy from the manufacturer’s factory service manual, it may not be the exact diagram for your particular model/year/options. You are in the best position to decide for yourself how sensitive you are to wiring diagram imperfections. Another idea, suggest to stop by your local public library. They may have the applicable Haynes or Chilton’s manuals you can reference there. Also ask the staff if they have any other auto-repair reference materials, such as on-line reference sources. ---
**Author:** ![Nevada\_545](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/nevada_545/32/41232_2.png) [@Nevada\_545](https://community.cartalk.com/u/Nevada_545)\ **Post date:** [March 7, 2023, 9:55pm UTC](https://community.cartalk.com/t/need-wiring-diagram-99-pontiac-grand-prix-se-trunk-light/189449/38 "2023-03-07T21:55:40Z")
> [@realrobd](#): > > Lights do not come on when unlocking with the fob. Only when opening the door. Illuminated entry is a standard feature, you must be experiencing a malfunction. ![image](https://global.discourse-cdn.com/cartalk/original/3X/e/d/ed8adbadb737a84b1144d9664c922551240f6633.png) ---
**Author:** ![realrobd](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/realrobd/32/34389_2.png) [@realrobd](https://community.cartalk.com/u/realrobd)\ **Post date:** [March 7, 2023, 10:21pm UTC](https://community.cartalk.com/t/need-wiring-diagram-99-pontiac-grand-prix-se-trunk-light/189449/39 "2023-03-07T22:21:38Z")
Looking at the manual, I can confirm this should be the case. The plot thickens. 😒 ---
**Author:** ![George\_San\_Jose1](https://avatars.discourse-cdn.com/v4/letter/g/e5b9ba/32.png) [@George\_San\_Jose1](https://community.cartalk.com/u/George_San_Jose1)\ **Post date:** [March 7, 2023, 10:51pm UTC](https://community.cartalk.com/t/need-wiring-diagram-99-pontiac-grand-prix-se-trunk-light/189449/40 "2023-03-07T22:51:39Z")
Do any interior lights at all turn on after unlocking a door using the remote? I presume you can unlock the doors that way, right? [Previous page](https://community.cartalk.com/t/need-wiring-diagram-99-pontiac-grand-prix-se-trunk-light/189449.md?page=1) [Next page](https://community.cartalk.com/t/need-wiring-diagram-99-pontiac-grand-prix-se-trunk-light/189449.md?page=3)