How To - Build a 4L80E Transmission Controller with an IO12 & Harness

How To - Build a 4L80E Transmission Controller with an IO12 & Harness

Using an IO12 to control a 4L80E transmission is simple, proven, and the harness is straightforward enough to build using an IO12 flying lead harness.

You’ll need the following:
- IO12 Flying Lead Harness (HT-049902)
- 4L80E Connector Pigtail (From ICT Billet - WPTRA38)
Pressure Sensors and Connectors
- DTM Deutsch Connectors (Optional)
- Loom, Tape, Glue Shrink, Zipties (HT-039300)
- Crimp Connectors or Solder/Iron
- Crimpers
- Strippers
- Heat Gun
- Scissors/Knife

Start by prepping the IO12 harness. Separate the following wires from the main bulk of the wiring:

Sig GND, Batt GND, 12V Batt, 12V Switched, DPI4 Bundle (Sig GND & 12V) AVI4 Bundle (Sig GND & 5V)

The Battery, Grounds, and Switched power will be connected per the IO12 Directions.

DPI4 and AVI4 will not be used in controlling the 4L80E and can be used as additional/spare inputs for other functions. It is recommended to Install a DTM3 connector on DPI4, and a DTM3 or Pressure Sensor connector on AVI4. Or at a minimum, Shrink up the 12V and 5V wires to prevent shorting out.

Remove the Labels from all 4 DPO bundles, AVI1, and DPI 1-3.

Leave AVI2 and AVI3 bundled with their respective 5V and Sig GND. These will be terminated but won’t connect to the OEM 4L80E connector.

The 4L80E Main Connector has the Shift Solenoids Control, Temp Sensor, TFP Pressure switch connections. It has 11 pins that need to be connected to the IO12 harness.

Sol A A Lt Grn DPO1 Purple/Black
Sol B B Yel/Blk DPO2 Purple/Bown
Line Press Sol Power C Red/Blk 12v Grey/Red
Line Press Sol Ground D Lt Blu/Wht DPO3 Purple/Red
12V Solenoids Power E Pnk 12v Grey/Red
Temp Signal L Yel/Blk AVI1 Orange/Green
Temp Sensor Ground M Gry Signal Ground Black/White
TFP Switch N N Pnk DPI1 Grey (Shielded)
Switch P P Red/Blk DPI2 Grey/Black (Shielded)
Switch R R Dk Blu DPI3 Grey/Brown (Shielded)
Lockup Solenoid S Brn

Separate out the necessary IO12 harness wires that will be connecting to the 4L80 main connector, from which you removed the labels, and measure from the end of those wires and shorten those by 24”.

Next, make your connections between the IO harness and the 4L80E pigtail harness, according to the chart above.

The DPI Wires are shielded with a grounded shielding wire. Be sure to separate that shield wire and make the connection to the inner signal wire ONLY.

Now Put pressure sensor connectors on AVI2 and AVI3.  These will be used for Line/Case pressure and converter/charge pressure.

The AVI2 & AVI3 harnesses should separate from the main Loom about 24” back from the main connector. These should be separated from each other so they can connect to the pressure sensors. 

There will be a number of extra Sig Gnd wires, 5v and 12V power wires that were not used. Cut those off and tape or shrink up the connections. Make sure none of the cut wires can ground out.

Finally, Loom and tape the harness and make it look nice.

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