Adding the exterior switch
In the U.S., with the Advanced Keyless Entry (AKE) option, in addition to the trunk release switch in the interior (near the hood release lever), our 124 Spiders also gain another switch on the underside overhang of the trunk lid itself in-between the pair of license plate lamps and, if you have the Infotainment system, to the right of the ParkView reverse camera. Mazda has thus far decided to exclude that switch in MX-5s for some markets (like Canada), leaving only the interior switch to release the trunk lid.
Just in case Fiat has also chosen to exclude that switch in some markets (limited feedback indicates that Fiat includes this switch with the AKE option across all markets), I’m bringing up a solution that Sergey (ssh16) has come up with as a nice alternative, and that JumperThumper has verified in his Canadian MX-5, which involves “piggybacking” the exterior switch (don’t know the Fiat part number, but the Mazda part number is N243-56-8D0) with the interior switch, as the wiring back to the Body Control Module (BCM, inconveniently located behind the left kick panel in close proximity to the interior fuse panel) should already be in place.
The piggybacked switch will actually be more convenient than the intended application, as you won’t need to have the key on your person to activate the exterior switch. It will work whenever the interior switch is allowed to work ⇒ whenever the vehicle is unlocked. When the vehicle is locked, both trunk release switches will be deactivated.
So just how did he accomplish this? He made a jumper wire (≈6″ long) that connects together:
- the yellow wire connected to the exterior switch that is plugged into terminal “2S” on the BCM
- the Brown/Green wire connected to the interior switch that is plugged into “3U” of the same BCM.
There are links to wiring diagrams and illustrations in the referenced thread.
Adding the interior switch
For those that have wiring leading to a dummy insert (as pictured below) rather than an actual interior switch (Europe and Australia market?), a few readers have already discovered that purchasing and installing an interior switch (Mazda part number GJR9-66-630A) and plugging in the harness will not enable it’s function.
However, I’m happy to report that collincn has verified that Sergey’s inverse solution ⇒ piggybacking the added interior switch to the exterior switch (as illustrated above) will enable the interior switch to function, although only if you have the key on your person, as is required with the exterior switch, as reported in the same aforementioned thread.