Toyota Tundra Service Manual: Diagnosis System

DIAGNOSIS SYSTEM

1. DESCRIPTION

The 4 wheel drive control ECU records DTCs when the ECU detects a malfunction in the ECU itself or in system circuits.

The DTCs can be read through the DLC3 of the vehicle. When the system seems to be malfunctioning, use the Techstream to check for malfunctions and perform troubleshooting.

2. CHECK DLC3

(a) Inspect the battery voltage.

Standard voltage:

11 to 14 V

If the voltage is below 11 V, recharge the battery before proceeding.

(b) Check the DLC3 (See page ).

3. FUNCTION OF INDICATOR LIGHT

(a) When a problem occurs in the touch select 2-4 and high-low system, the 4HI and 4LO indicator lights on the combination meter assembly rapidly blink* to inform the driver of the problem.

  • *: 0.25 second intervals (0.25 seconds on and 0.25 seconds off)
    4WD Control Switch Circuit

    Diagnostic Trouble Code Chart

    See More:

    Toyota Tundra Service Manual > Lighting System: Headlight Dimmer Switch Circuit
    DESCRIPTION The main body ECU (multiplex network body ECU) receives the following signals: Light control switch in off*1, DRL-Off*2, tail, head or Auto position Headlight dimmer switch in high, low or high flash (pass) position Fog light switch front position*3 *1: w/o DRL Off Switch *2: w/ DRL Off ...

    Toyota Tundra Owners Manual

    Toyota Tundra Service Manual

    © 2026 Copyright www.ttundra.com
    0.0105