Toyota Tacoma (2015-2018) Service Manual: System Description
SYSTEM DESCRIPTION
1. DESCRIPTION
- A part-time 2-speed VF2CM transfer uses a touch select 2-4 and high-low system, enabling the driver to switch between 2WD, H4 and L4 modes by turning the transfer position switch.
- Through these switch signals, the 4 wheel drive control ECU actuates the shift motor in the transfer shift actuator and another shift motor in the A.D.D. actuator (differential vacuum actuator assembly).
- When driving in 4WD at high speeds on dry pavement, the front differential oil temperature may rise excessively, resulting in oil leaks or seizures. To avoid such occurrences, the 4 wheel drive control ECU monitors the oil temperature via the front differential oil temperature sensor and provides a front differential temperature warning using a message and the warning buzzer.
2. DRIVING MODE SWITCHING PATTERN
Text in Illustration
|
*1 |
Transfer Position Switch |
- |
- |
3. INDICATOR LIGHT, WARNING MESSAGE AND WARNING BUZZER OPERATING CONDITIONS
2WD/4WD Mode Control|
Mode |
4WD Indicator Light (Green) |
4LO Indicator Light |
Multi-information Display Message |
Warning Buzzer |
|---|---|---|---|---|
|
2WD |
Not illuminated |
Not illuminated |
- |
Not sounding |
|
While switching between 2WD and H4 |
Blinking |
Not illuminated |
- |
Not sounding |
|
H4 |
Illuminated |
Not illuminated |
- |
Not sounding |
|
While switching between H4 and L4 |
Illuminated |
Blinking |
- |
Not sounding |
|
L4 |
Illuminated |
Illuminated |
- |
Not sounding |
|
A.D.D. Actuator malfunction |
Not illuminated |
Not illuminated |
2WD-4WD mode change malfunction visit your dealer |
Not sounding |
|
High-Low malfunction |
Status displayed*1 |
Rapidly blinking |
- |
Not sounding |
|
Other switching malfunction*2 |
Not illuminated |
Rapidly blinking |
2WD-4WD mode change malfunction visit your dealer |
Not sounding |
- *1: Displays the 2WD/4WD mode status during a malfunction
- *2: Malfunctions not listed in "Mode" or "Control Mode"
- Blinking: Blinks at 0.5 second intervals (0.5 seconds on and 0.5 seconds off)
- Rapidly blinking: Blinks at 0.25 second intervals (0.25 seconds on and 0.25 seconds off)
|
Control Mode |
2WD/4WD Mode Status |
4WD Indicator Light (Green) |
4LO Indicator Light |
Multi-information Display Message |
Warning Buzzer |
|---|---|---|---|---|---|
|
Front differential oil temperature warning starts |
H4 |
Illuminated |
Not illuminated |
Differential oil temp high Shift to 2WD mode Cooling time required |
Sounding |
|
L4 |
Illuminated |
Illuminated |
Differential oil temp high Shift to 2WD mode Cooling time required |
Sounding |
|
|
Vehicle speed limit control starts*1 |
H4 |
Illuminated |
Not illuminated |
Differential oil temp high Shift to 2WD mode Cooling time required |
Sounding |
|
L4 |
Illuminated |
Illuminated |
Differential oil temp high Shift to 2WD mode Cooling time required |
Sounding |
|
|
While switching to 2WD |
H4 |
Illuminated |
Not illuminated |
Differential oil temp high Shift to 2WD mode Cooling time required |
Sounding |
|
Switching to 2WD complete |
2WD |
Not illuminated |
Not illuminated |
Differential oil temp high Cooling time required |
Sounding finished |
|
Vehicle speed limit control finished |
2WD |
Not illuminated |
Not illuminated |
- |
Not sounding |
|
Front differential oil temperature sensor malfunction |
- |
Not illuminated |
Status displayed*2 |
2WD-4WD mode change malfunction visit your dealer |
Not sounding |
- *1: 30 seconds after front differential oil temperature warning starts
- *2: Displays the 2WD/4WD mode status during a malfunction
4. FUNCTION OF COMPONENTS
|
Components |
Functions |
|
|---|---|---|
|
Transfer position switch |
Switches between the following 3 drive modes: 2WD, H4 and L4. |
|
|
Combination meter assembly |
4WD indicator light (green) |
Illuminates to inform the user of 4WD mode status. Blinks to inform the user of mode switching. |
|
Multi-information display |
Displays a malfunction message to inform the user of a system malfunction. Displays a message to inform the user of a front differential oil temperature warning. |
|
|
4LO indicator light |
Illuminates to inform the user of L4 mode status. Blinks to inform the user of mode switching. Rapidly blinks to inform the user of a system malfunction. |
|
|
Warning buzzer |
Sounds to inform the user of a front differential oil temperature warning or switching condition violation. |
|
|
Skid control ECU (brake actuator assembly) |
Outputs wheel speed signals to the 4 wheel drive control ECU via CAN communication. |
|
|
ECM |
Outputs information such as the shift lever position and engine speed to the 4 wheel drive control ECU via CAN communication. |
|
|
Clutch start switch assembly (for Manual Transmission) |
Detects clutch pedal depression and sends that information to the 4 wheel drive control ECU. |
|
|
4 wheel drive control ECU |
Detects the vehicle status from wheel speed signals, vehicle speed signals, etc. received via CAN communication, and switches to the requested 4WD mode (H4 or L4) by operating the transfer shift actuator assembly and A.D.D. actuator (differential vacuum actuator assembly) according to the operation of the transfer position switch. |
|
|
Transfer shift actuator assembly |
Transfer shift motor and limit switch |
Operates the shift motor according to commands sent from the 4 wheel drive control ECU and switches to 4WD mode (H4 or L4). |
|
4WD detection switch |
Detects the 4WD condition and sends that information to the 4 wheel drive control ECU. |
|
|
L4 detection switch |
Detects the low gear position and sends that information to the 4 wheel drive control ECU. |
|
|
A.D.D. actuator (differential vacuum actuator assembly) |
A.D.D. shift motor and limit switch |
Operates the A.D.D. shift motor according to commands sent from the 4 wheel drive control ECU and switches between 2WD and 4WD. |
|
A.D.D. position switch |
Detects the 2WD and 4WD A.D.D. positions and sends that information to the 4 wheel drive control ECU. |
|
|
Oil temperature sensor |
Detects the oil temperature in the front differential. |
|
- Blinking: Blinks at 0.5 second intervals (0.5 seconds on and 0.5 seconds off)
- Rapidly blinking: Blinks at 0.25 second intervals (0.25 seconds on and 0.25 seconds off)
How To Proceed With Troubleshooting
CAUTION / NOTICE / HINT
HINT:
Use the following procedure listed to troubleshoot the touch select
2-4 and high-low system.
*: Use the Techstream.
PROCEDURE
1.
...
System Diagram
SYSTEM DIAGRAM
Transmitting ECU (Transmitter)
Receiving ECU
Signal
Communication Method
4 wheel drive control ECU
Skid ...
Other materials:
Occupant Classification ECU Malfunction (B1795)
DESCRIPTION
DTC B1795 is set when a malfunction is detected in the occupant detection ECU.
Troubleshoot DTC B1771 first when both DTCs B1771 and B1795 are present.
DTC No.
DTC Detections Conditions
Trouble Areas
B1795
Occupant detection ...
Terminals Of Ecu
TERMINALS OF ECU
1. COMBINATION METER ASSEMBLY
(a) Measure the voltage, resistance and check for pulses according to the value(s)
in the table below.
Terminal No. (Symbol)
Wiring Color
Terminal Description
Condition
Specified Condition
...
No Sound can be Heard from Speakers
PROCEDURE
1.
CHECK AUDIO SETTINGS
(a) In sound output setting mode, set volume, fader and balance to the initial
values and check that the sound is normal.
OK:
Audio system returns to normal.
HINT:
Sound quality adjustment measures vary according to the type ...
