The M1 connector or "Small Yellow Connector"
There are 5 wires you need from this connector
Yellow/Black - yellow with a black stripe - oil pressure for guage and ECU
Yellow/Green - Yellow with a green stripe - Water temp for guage
Pink - Pink Wire - speed sensor from Combonation Meter.
Green/Gray - Green with gray stripe - Engine light
black - Tach (tach mod may be required) Click here for details for 3VZE-7MGTE mod.
Water Temp
The water temp wire, yellow with black stripe is used for your guage only. This is not the temp sensor used for your ECU, so if you get a water temp error on your codes, this is not where you want to look to solve your problem. All toyota vehicles use this color wire for the temp guage, so your swap vehicle will have the same color wire.
Oil Pressure
The same is also true with the Oil Pressure wire. This comes from the oil pressure sending unit and will always be the same color. Yellow with black stripe. On the 7M, this also feeds into the ECU. I am not really sure why the ECU needs to know the oil pressure, as I have found it to have no impact on the way the engine runs whether or not it is hooked up to the ECU.
In fact, your guage might not even work if it runs through the ECU. You also may need to use your Oil sending unit from your old motor.
They are calibrated for the guage on your vehicle. These are pretty easy to change with a 14mm open end wrench, or a very large socket.
Engine Light
The Engine light requires a ground signal from the ECU. This is a black wire. Simple as that. Check your vehicles wiring diagram to figure out what what that is. The 7M uses the black wire, but on other vehicles, I have seen many different colors used.
With the engine light, you can run your diagnostic codes, or engine codes by connecting TE and E1 in your "Check Connector" near the igniter. When you turn your ignition on, your light will flash codes. Here is a link for your Diagnostic Codes
Speed Sensor
The Speed Sensor wire, green with gray strip, comes from the Spedometer from your instrument cluster. This is how the ECU knows how fast your are going. I have noted, that connecting this wire will help with stalling.
The wire between the M1 connector and the ECU is pink, but the wire between the M1 connector and the Spedometer could be a range of colors. Refer to your vehicles electrical schematic to figure this out(EFI ONLY).
Tachometer
The Tach wire, black wire, does NOT come from the ECU, and it does NOT go to the ECU.
A signal wire goes directly from the igniter to your tach guage. You can also test this signal from the IG- terminal in the "Check Connector" near the igniter. And again, here is a link for the 3VZE tach mod. Tach Mod