Lexus V8 Engines LLC2005 Tundra Transfer Case Control Unit Client Plug Guide
Transfer Case Control and Front Differential ADD Reference
2005 Toyota Tundra 4WD control unit harness setup
Build-Specific Confirmation
Always confirm connector orientation, terminal location, wire color, circuit function, signal direction, polarity, fuse protection, and build-specific instructions before final installation. Do not wire by color alone.
Connector Visuals
Overview
This document provides the customer-side reference for the transfer case control unit client plugs used on supported 2005 Tundra-based 4WD control systems.
The 4-pin plug is used for 2WD/4WD and high/low control wiring with 4LO and 4HI dashboard indicators. The 6-pin plug is dedicated to front differential ADD actuator/detection wiring.
Important
This guide covers the vehicle-side transfer case control unit client plugs used with the 2005 Toyota Tundra 4WD control unit harness setup. It covers the 4-pin control/indicator plug and the 6-pin front differential ADD plug. It is not a full chassis or body harness.
General Information Notice
This document is provided for general information and customer reference only. Final wiring must be verified against the exact harness supplied and the vehicle-side circuit being connected.
Quick Start: Critical Connections
| Function Group | Circuit / Pin | Wire(s) | Customer Connection |
|---|---|---|---|
| 4-Pin Control / Indicator | 4LO indicator, 2WD/4WD control, high/low control, 4HI indicator | Pins 1-4 | Connect to vehicle-side 4WD switch/control panel and dash indicator circuits as configured. |
| 6-Pin Front Differential ADD | ADD actuator and position wiring | Pins 1-6 | Connect only to the matching front differential ADD actuator/detection wiring as supplied. |
| Factory Diagram Reference | Toyota 4WD control reference | Appendix/reference only | Use factory diagrams as reference only. Always follow supplied harness pinout first. |
Wire Color / Tracer Reference
Stripe/tracer colors are shown as diagonal bands on the wire. The first color is the base wire color. The second color is the stripe/tracer color.
Full Pinout Reference
| Pin | Wire Visual | Circuit / Function | Signal Type | Notes |
|---|---|---|---|---|
| 4-Pin Pin 1 | Pink / Black | 4LO Indicator Light | Dashboard 4 Low indicator | Low-current indicator circuit. Confirm dash light polarity before connecting. |
| 4-Pin Pin 2 | Pink | 2×4 / 4×4 Control | 2WD/4WD select switch or control panel | Control/request circuit used for selecting between 2WD and 4WD operation as configured. |
| 4-Pin Pin 3 | Green / Yellow | High Range / Low Range Control | High/Low range select switch or control panel | Control/request circuit used for high/low range selection as configured. |
| 4-Pin Pin 4 | Yellow / Black | 4HI Indicator Light | Dashboard 4 High indicator | Low-current indicator circuit. Confirm dash light polarity before connecting. |
| 6-Pin Pin 1 | Red | Front Differential ADD Circuit | ADD actuator/detection wiring | Connect to matching front differential ADD circuit as supplied. |
| 6-Pin Pin 2 | Red / White | Front Differential ADD Circuit | ADD actuator/detection wiring | Connect to matching front differential ADD circuit as supplied. |
| 6-Pin Pin 3 | Gray | Front Differential ADD Circuit | ADD actuator/detection wiring | Connect to matching front differential ADD circuit as supplied. |
| 6-Pin Pin 4 | Brown | Front Differential ADD Circuit | ADD actuator/detection wiring | Connect to matching front differential ADD circuit as supplied. |
| 6-Pin Pin 5 | Red / Black | Front Differential ADD Circuit | ADD actuator/detection wiring | Connect to matching front differential ADD circuit as supplied. |
| 6-Pin Pin 6 | Green | Front Differential ADD Circuit | ADD actuator/detection wiring | Connect to matching front differential ADD circuit as supplied. |
Detailed Circuit Notes
4-Pin control and indicator plug
- Pin 1 Pink/Black is the 4LO indicator circuit.
- Pin 2 Pink is the 2×4/4×4 control/request circuit.
- Pin 3 Green/Yellow is the high/low control/request circuit.
- Pin 4 Yellow/Black is the 4HI indicator circuit.
6-Pin ADD plug
- The 6-pin connector is dedicated to the front differential ADD system only.
- Connect pin-for-pin to the matching ADD actuator/detection wiring supplied with the harness.
- If receiving vehicle wiring is modified or missing, confirm ADD actuator and detection wiring before connecting.
First Test Checklist
| Item | Check |
|---|---|
| Pinout | All pin locations match the supplied harness before final connection. |
| 4LO Indicator | Pink/Black operates only when 4 Low indication is expected. |
| 2×4 / 4×4 Control | Pink control circuit changes state correctly when switch is operated. |
| High / Low Control | Green/Yellow control circuit changes state correctly. |
| 4HI Indicator | Yellow/Black indicator operates only when 4 High indication is expected. |
| Front Differential ADD | 6-pin ADD plug is connected to correct actuator/detection wiring. |
Troubleshooting Quick Reference
| Symptom | Items to Check |
|---|---|
| 4WD will not engage | Check 2×4/4×4 control input, 4WD ECU power/ground, transfer actuator wiring, neutral input, speed input, and ADD connection. |
| 4LO will not engage | Check high/low control input, Park/Neutral input, vehicle speed conditions, transfer actuator wiring, and 4LO detection. |
| 4HI or 4LO light does not work | Check indicator wire, dash polarity, lamp/LED feed, and whether the 4WD ECU is commanding the indicator. |
| Front differential does not engage | Check 6-pin ADD plug, actuator wiring, actuator motor operation, detection switch, and 4WD ECU outputs. |