I can't find it . Someone said it is just in front of the battery, maybe tomorrow I will take the battery out and try and get a better look around. The FSM says there is one inside the vehicle as well, anyone know where? My ECU is up under the (my) drivers side in the footwell. There is a connector right next to it but it seems to have too many wires. My car is a base model, no electric windows, no a/c no central locking, just lots of empty plugs and sockets coming off the wiring loom.

Edit: Maybe they changed the plug type, my car has the coded ignition key, I wonder if they brought a couple of wires out to recode it?

I know there is one just behind what would be "your" driver's side headlight. I used a jumper wire from pin 4 and 5 while checking my timing but that is on a '96.

On my 94 there is a 4 pin terminal right in front of the batery cliped to a rubber boot on the relay block.  If you ground one of the terminals it forces the trouble codes to blink on the check engine light.  I have a list of what the codes mean but its only for 94's I think.

I know there is one just behind what would be "your" driver's side headlight. I used a jumper wire from pin 4 and 5 while checking my timing but that is on a '96.

Tell me more, my FSM says it is a 4 pin connector but there is a 6 pin connector there that has some of the correct colors
A 96 is a 16V? I am trying to monitor the ISC duty cycle output on the TBI.

On my 89' the "DIAG" terminal is
in the fuse block, and says Diag
right on it, just install a fuse and
read the blinks, FWIW the Diag
is only good for smog related stuff,
bad O2, EGR Etc. the computer cannot
diagnose it's self, if that's what you
are looking for

Wild

. the computer cannot
diagnose it's self, if that's what you
are looking for

Wild

My FSM says that if you put a jumper across two of the terminals you get the ISC duty cycle output. I'm guessing it just buffers the signal going to the ISC. I know it should be around 50% at idle with the engine temp norm but I don't know what frequency it operates at. I'll try and have another look tonight.

Well I had another look and I found the terminal, first prize to Trackermad  



Its down there in front of the battery, almost under the fuse terminal. Trouble is I can only get to it if I take the battery out cos I put the winch solenoid box over the strut top on that side   . I pulled the plug off the ISC and I didn't get a CEL so assuming unplugging it doesn't affect its operation I stuck a scope on it.



It looks pretty much as I was expecting - at idle, engine warm its a bit over 50% but the revs were down a bit. Frequency comes in around 2KHz, voltage was 12V but doesn't show up too well using a x10 probe. Unplugging it made no noticeable difference to the idle stability, thought the speed shot up for a few seconds when I plugged it back in with the engine running.