How To: Change trunk wiring harness on S40
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    1. #1
      Junior Member Volvorite's Avatar
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      Exclamation How To: Change trunk wiring harness on S40

      Forum member ewizzle wrote up a good post describing the common trunk wiring harness problem with Volvo S40's. It is a common point of failure for these vehicles because of a [in my opinion] poor design, but something that is easily replaceable. If your trunk latch stops opening the trunk, this is a great place to start. Replacement harness's can be found online.

      Difficultly rating: 3 (Really just one annoying part)
      (1 is air filter changing and 10 is engine rebuild)

      Approximate Duration: 1 hour for the inexperienced, ~30 min if you know what you are doing

      Parts Needed:
      * Replacement trunk harness (Part #8697604), found for about ~$40 (USD) online

      Tools Needed:
      * A pair of Needlenose Pliers (the longer the "needlenose" section, the better)
      * flat head screw driver
      * Scissors, garden shears, or similar cutting device
      *nimble fingers
      ________________________________________________
      I completed this replacement in ~1 hour this past weekend on my 2006 Volvo S40, and saved a ton of money in the process.

      Steps:
      1. Pop open the trunk (if the latch is broken, you may have to crawl in from the back seats and pull the emergency release lever)

      view of the trunk door interior. Note location of emergency release lever and

      2. Remove the trunk door interior by removing the 12 plastic press-fit fasteners. This can be done with your hands or with a pair of pliers:


      3. Remove the Trunk latch cover, snake the emergency trunk release latch through the carpet, and remove the trunk lid carpet:


      4. With the carpet removed, the harness (and it's 3 attach points) will be in full view. Disconnect it from the trunk lid at the the trunk latch and license plate lighting connectors. The license plate lighting connector may give you some trouble, as it is hard to get at. I put a long, narrow flathead screw driver up the manipulation hole, and looked through an eye hole as shown below:


      5. Pop out both harness seals (where the harness goes from the trunk door to the car body. Their locations can be seen:


      6. Reach in under the sheetmetal over the driver side tail light and disconnect the harness from the body connector.

      7. Now that the harness is disconnected from it's electrical plugs, use a pair of scissors, shears, or piers to yank out all the harness retainers.

      8. Basically reverse the process, connecting the new harness at the 3 plug attachment points and securing in the new harness retainer clips:


      9. Go grab a cold beverage and enjoy the $$$ savings you earned from doing it yourself
      ____________
      As a final note, thanks to user Dextrobrick for sending me some initial instructions to go off of.

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    3. #2
      Member TG's Avatar
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      Hey, good work on this.
      It has been discussed but never has there been a write-up.
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    4. #3
      Member EngTech's Avatar
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      Nice Clear - Pic's and Labels : We need more electrical Stickies .

      Add Notes .

      What was the Cause , I mean I see broken Wire casings , but looked like they got Pitched .
      At least on other Post .

      Wonder If this is a Sedan Only Issue any Wagons having this ?
      Last edited by EngTech; 05-13-2013 at 08:44 PM.
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    6. #4
      Member Jexx's Avatar
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      What is the annoying/difficult part, exactly?
      2006 S60R GT

    7. #5
      Moderator aldebaran's Avatar
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      Thanks for the write up. Stickied this.

    8. #6
      Junior Member Volvorite's Avatar
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      Thanks for the praise all!

      Jexx- The annoying part is the removal and re-connecting of the license plate lighting attachment point. It is located behind some metal, and there are only the 2 small holes (the "manipulation point" and "eye hole" in the photo) from which to see.

      EngTech- You are right, I'm fairly certain it broke from extended use/pinching of the harness. The design itself leaves the harnesses open for easy pinching between the trunk door and the car body.

    9. #7
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      trunk lid open

      Would this fix the "Trunk Lid Open" message on my dash despite it being closed and fully latched?

    10. #8
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      Anybody?

    11. #9
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      Great write up!

      I removed the 4 T25 screws above the license plate so I can easily remove and reconnect the connector to the license plate lights / truck release button instead of using the eye hole.

    12. #10
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      Easier way to fix: cut out and replace broken wiring. Cheapest solution by far.

    13. #11
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      Quote Originally Posted by CRAMMER View Post
      Great write up!

      I removed the 4 T25 screws above the license plate so I can easily remove and reconnect the connector to the license plate lights / truck release button instead of using the eye hole.
      this is exactly what i plan on doing. i took everything apart and this reinstall should take no more than 30 minutes.

      thank you forums for helping me save a ton of money!

    14. #12
      Junior Member kasozi10's Avatar
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      Unfortunately I do not have the emergency trunk release.... Apparently some Canadian models did not get one for 2006... and my trunk will not open.

    15. #13
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      Sorry to resurrect an oldie, but I have the same problem, no emergency trunk release. You able to fix yours on your own?

    16. #14
      Junior Member tilley's Avatar
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      Canadian Cars:

      My understanding is that NO Canadian cars have the internal emergency trunk release (not a requirement maybe? So Volvo saves money by not installing it? Really?? So now Volvo has to have different latches fabricated, catalogued and stocked? I don't get the logic). Being thoroughly upset with this situation, I ordered a US latch (has an extra part with release cable), and the separate glow in the dark handle. It's been a few years since I installed the US parts, but from what I can remember, I had to have the dealer get the trunk open initially and they offered to do a temporary fix to the wiring harness (they charged me about C$40). I then retrofitted the latch with the US model (1.5 on 10 level of difficulty). Harness is now acting up again so it's great having a way to open the trunk while I explore whether to install a new harness, or fix existing harness.
      2005 S40 T5 AWD M6

    17. #15
      Member thefisch33's Avatar
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      I'm doing this now. To say crappy wiring is an understatement. Look at my picture where the wires are just connected by tape!


      '10 s40 m66 awd
      '12 c30
      2010 s40 T5 AWD M66 a tribute to Heico's ODIN HS4

    18. #16
      Looks like it might have been repaired before!
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    19. #17
      Member thefisch33's Avatar
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      Upon closer inspection, it's a 3 way connection and appears to be factory welded, so it was secure. The issue is they used too stiff of wire, so the rubber ends up fracturing.


      '10 s40 m66 awd
      '12 c30
      2010 s40 T5 AWD M66 a tribute to Heico's ODIN HS4

    20. #18
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      Thumbs up 2010 S40 harness repair

      Quote Originally Posted by thefisch33 View Post
      I'm doing this now. To say crappy wiring is an understatement. Look at my picture where the wires are just connected by tape!


      '10 s40 m66 awd
      '12 c30
      Thanks for the pics. My S40 had the same issue (one wire severed, one wire severely frayed). Took me 30 minutes to spice the wires and button everything back up.

      My wallet & I both thank you.

    21. #19
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      I had to do this at the beginning of the summer. I just ordered a new harness. Some of my plastic trunk carpet fastners did not survive me pulling them out.. Is there a cheap replacement part vs a Volvo part?

      Also its much easier to attach the end of the cable by taking off the License Plate light section so you can just plug it up with out having to stick adult hands inside that small area

      See below for Pics
      Last edited by kazman; 04-09-2018 at 04:14 PM.

    22. #20
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      Quote Originally Posted by kazman View Post
      I had to do this at the beginning of the summer. I just ordered a new harness. Some of my plastic trunk carpet fastners did not survive me pulling them out.. Is there a cheap replacement part vs a Volvo part?

      Also its much easier to attach the end of the cable by taking off the License Plate light section so you can just plug it up with out having to stick adult hands inside that small area

      My lack of access to photo sharing sites at work limits my options.. Hopefully you can see 2 pictures in this album ....

      https://1drv.ms/i/s!AmIPLfp3XIOQjOUUtDlR1Ow5bMcPEA

      Only see one (pre or post photo of the license plate light housing installed).

    23. #21
      Member pczeilon's Avatar
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      Just remove the 4 screws, it comes right off.
      2007 V70 5 Speed
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    24. #22
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      Remove the 4 screws




      And then gain access to the plug

      Last edited by kazman; 04-09-2018 at 04:12 PM.

    25. #23
      Junior Member jonasbuchholz's Avatar
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      For all those that don't have the trunk release, it's still easy. I just changed mine. Just crawl in from the front (fold the seats down). And start by removing the carpet that is covering the latch after that take off the connector for the harness that is right under the rear window. Then take off the connector that is on the lock, now just take out the 4 torx 25 that are right over the license plate and you can get the whole thingy with the license plate lights out. and remove the connector to the switch for the lock. Now you can just temporarely connect the new wire harness to all the connectors and you can open your trunk again.
      2004 Volvo s40 2.4 - Dawn blue pearl

    26. #24
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      Very helpful thread - thank you.
      I was receiving 'Boot Lid Open' message on S40 2008 even though it was firmly closed and hazard lights were not flashing when the car was being locked.
      Turned out one cable was completely broken and all other others were damaged in 2 places.

    27. #25
      I did skip 1 of the reattachment points and did a nice wide loop into the plug for the harness on my end. It's not good in that unlike the stock setup, if I slide something in the trunk, I can hook the harness and cause an issue. It's flat and flush with the roof of the trunk so it's not likely but it is possible. On the bright side, the harness will not vibrate itself to the sheetmetal and cut the wires over time.

      Something also to consider, what I did too, is put some of those door edge guards from walmart on the sheetmetal and remove that sharp edge from rubbing on the wires and causing a short, in case an owner behind me has to replace the harness and does it the right way, it should last forever at that point.
      2006 Volvo S40 AWD T5 M66 - Dusty Rusty
      2012 Subaru Outback 2.5i CVT - Slowmobile - CAI only, Powerstop Rotors+Pads.
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