Agu in mk3 8v gti

you leave most of the mk3 wiring loom alone, as its all integrated on the post-96 it includes fan switch, lights etc etc that all stays as it was before. coil you dont need so you can cut that plug, then you have 1 wire from it to ecu which you bin as its now loose, an ignition live and earth. ignition live could go to coilpacks but I recommend you put a fuse inline as per my guide at least. earth can go to t10a plug for your coilpack earth.

aircon stays as it is if keeping aircon, you have 1 or 2 ecu wires for your mk3 aircon which need to go to the agu ecu aircon wire(s) so it knows the aircon is switched on

then all you worry about is the wiring to the mk3 ecu and the engine round plug, these are all the feeds you need for the agu ecu

 

Any wires from ECU to round plug can go, any wires from fusebox to ecu plug can be used for the coloured plugs or will be spare. Any wires from round plug to fusebox can be used for the t10a.

Use my fusebox faq and my MK4 guide to figure out what all the fusrbox wires are for

brown wires to ecu and coil can be reused for the ECU and t10a these are earthstry James e looms or William Skelton on facebook

 

yes, you only use the mk4 ecu

 

follow all the wires that used to be on the round plug, use my fusebox FAQ to ID what they are. the thickish red with big yellow spade plug hosuing at fusebox end is Z/1 which is your fuel injector live.

you may have one wire from round plug to the fan control module, thats radiator fan after-run thermoswitch. you can either insulate this and ignore, or mount the mk3 thermoswitch near the exhaust manifold and have the feature working

 

any wiring that came from big ecu plug to stuff in the engine bay, can go. so ecu -> round plug, bin. ecu -> carbon canister -> bin. ecu -> airbox, bin. cut the plugs off for any of these, then you'll be left with some wires from these things to the fusebox. use fusebox faq to ID what they are

so for example, the carbon canister has 1 wire to ecu, and 1 wire to g2/4 which is ignition live. keep this handy, but you may find you dont need it. lambda probe has 2 wires from ecu, an earth which you may or may not need keep handy, and wire from g1/8 which is fuel pump power for lambda heater -> use for agu lambda and maf plus carbon canister feed.

key is dont panic, dont cut anything except ecu plug, round engine plug and any plugs in engine bay that are fed from ecu plug.

fusebox side from ecu you'll have some to G1/G2/F, plus some singles. a purple/white wire is mpg signal, you could try tapping this to the agu mpg signal mixed reviews if it works or not. blue/white vehicle speed signal wire, tap that to agu blue/white.

grey/white is your diagnostics wire, it will go to the immobiliser box but that can go in the bin now instead you could run ecu diagnostics straight to the jumper block above fusebox. or you could splice the mk3 grey/white wire to the agu grey/white and leave immo box in there, the agu ecu will ignore it and the immo box will still route vagcom port connection to the ecu just fine.

if you want to strip out immob box drag all the wires from the box out and reader coil from ignition switch. there will be black wire to the green E plug, can cut that off to remove the loom but DONT cut the other black wire from E plug which goes to ignition jumper block. you then splice immobiliser box wire to the diagnostics jumper to the ecu diagnostics wire then it plugs into the diagnotics block