FC3S Turbo II S4 to S5 Gauge Cluster Conversion Swap Re-pin
 

Remove all the wires from the S4 harness plug housings which will be behind the gauge cluster. Re-pin them using this diagram. You will be using the far left and far right plug pins on the back of the S5 cluster with the S4 harness (the middle plug pins of the S5 cluster will not be used).

This diagram will show you where each wire will need to be pinned for a Turbo manual transmission S5 gauge cluster. Each plug-pin wire will be lettered A-L. The letters can be found on the wiring-side of the plastic plug housings.

Re-pin procedure is as follows:

Black Plug
A: Black (ground)
B: Red/White (skinny)
C: Yellow/Red
D: Blue/White
E: Black/White
F: Yellow/White
G: *blank
H: *blank
I: Yellow/Blue
J: Green/Black
K: Red/White (large)
L: White/Green

White Plug
A: Green/Red
B: *blank (S5 ECU wire)
C: Blue (JDM harnesses won't have this wire)
D: Black (ground)
E: Red/Green
F: *blank
G: Green/White
H: *blank
I: Brown/White
J: Brown
K: *blank (S5 ECU wire)
L: Black/Yellow

Left over wires are most likely S4 cluster specific. If something fails to work, recheck this diagram a second and third time before throwing your gauge cluster to a brick wall. If this still fails to work, check a diagram from the legend himself, Icemark. He has a Non-Turbo conversion diagram that may have the necessary re-pin procedure for your gauge.