SOHC & CONSULT Clarification

[g6civcx]

I saw mrmephistopheles's FAQ about SOHC vs. DOHC CONSULT wiring, specifically this section:

1. Locate the body harness (under dash harness that attached to the ECU) that attached to your old harness. Cut the old connector off (the one that attached to your SOHC harness) and attach your DOHC body harness connector. Just match the colors! There will be some wires left over. These are for the SOHC's diagnostic plug, and are unnecessary. Please note: Your car will NOT be able to hook up to a CONSULT tool. To accomplish this, you must get a body harness with all the correct DOHC wiring. This is why we cut the body harness connector off, and not the engine harness connector.

Does this mean that the SOHC's diagnostic plug located behind the underdash fusebox will not plug into a CONSULT tool?

The reason I am asking is because I am rewiring my SOHC body harness for an SR. Should I cut off a CONSULT plug from a DOHC and wire it in, or can I use my existing diagnostic wiring and wire it to the SR ECU?

I searched and found this on FA:

There is no CONSULT port in your car ['89 SOHC]. The plug you speak of is probably black, that's an earlier type of diagnostic port that's not used much.
Since you have an SR, you can easily add the plug, it's five wires. Ground, ignition, TX, RX, and CLK. Any 91-up car will have the plug, cut it out and wire it right in at the ECU.

This is the plug. It's black with a purple cover, and has some wires that go to the SMJ and some that go to the ECU.

According to the FSM, these are the wires coming out of the diagnostic plug:

* Red, Green, Gray/Blue, Red/Yellow, Purple, Light Green, Grey, and Black all go to the ECU via the F1 plug. These are not connected to the SR ECU (except for Black for common ground). The FSM is not clear on what these should read on the KA.

* Black/White goes to ECCS Relay/CAS via SMJ.

* Black/Red goes to ignition power.

* Pink goes to AIV/ECU via SMJ.

I'm just going to remove all these unused wires from the body harness and solder the CONSULT plug straight to the ECU. The FSM isn't very clear about the pinout of the diagnostic plug so I would like to know if I should keep any of these wires for future use. Thanks for any help you can provide.

[mrmephistopheles]

The diagnostic doodad for 89-90s is for the ECCS system. Nissan dealerships have what's called a 'Checker Box' that they can plug into it.
Throw away the old plug and get one from a DOHC ECU/harness.

[g6civcx]

Okay, gotcha. It's all gone. Just FYI in case someone else was curious, 3 wires go straight to the SMJ for various sensors on the engine. They eventually go back around the engine bay and loop back to the ECU.

All the other wires go straight to the ECU, except for the CEL wire, which branches off to the gauge cluster. The SR doesn't have a pinout for a CEL so it's gone.

Other than that it's pretty simple to remove the SOHC diagnostic plug. I'll get a CONSULT plug and solder it to the SR ECU pinout. Thanks.

[ryan hagen]

ok, i m doing the same thing, on the dohc diagnotic port aka "nissan 2" port i found a set up for a sr, the colors seem be different, blu,yel,re,grn,white
but i dont know which wire is tx, tx seems to be green on my data port. where do i hook it up, on the ecu harness i found green/black and green/white which go to my data port. on this harness brown connector(dohc) where does the green/yellow go? it think it it is for a/c but am unsure.

1(rx) green/black : back to ecu
2(tx) green : ?????
3(gnd) black : to ecu ground or any ground
4(clk) green/white : back to ecu
5(12v) green/blue : ecu 12v or any fused 12v?

tx is the only one im lost on
what i did was cut a white connector(to chasis) from a sohc engine harness, and had a dohc chasis side connector and made a adpater, and i m trying to put the data link conector in this adapter.