NOTE ALL DIAGRAMS IN THIS GUIDE ARE FOR ONLY 2007 TOYOTA 4RUNNERS. THIS MAY WORK FOR OTHER MODELS (FJ, TACOMA) OR OTHER YEARS IN THE SAME GENERATION HOWEVER WIRE COLORS AND CONNECTION POINTS MAY DIFFER.
I had the unfortunate pleasure of experiencing the dreaded loss of power when the VSC kicked in after wheel slip when starting off from a stop. It's downright dangerous. After looking through the many VSC off mod threads and the Toyota schematics I've developed an alternative mod that seems to offer all the features of an OEM VSC OFF switch with no compromises.
Other mods make compromises such as:
- Requiring restart of the engine to reset.
- Showing a center diff Locked light when the center diff is not locked.
- Inability to use the mod in 2WD without a complex switching process.
- Potential issues with the 4WD and Skid Ctrl ECU self check process on startup.
- Disabling other features such as ATRAC and ABS while the mod is active.
This mod will operate regardless of the 4WD engagement, display correct center diff Lock status at all times and properly restart the 4WD ECU and Skid Ctrl ECU regardless of the mod’s state on engine start. It will also not add a parasitic draw to the battery when the truck is off.
See below for detailed instructions, explanations, and wiring diagrams.
TLDR: Cut the RED-BLUE STRIPE wire from the Skid Ctrl ECU. To the ECU side connect the RED-BLUE STRIPE wire to the pole of an SPDT relay. Connect the normally open relay contact to a ground point. Connect the normally closed relay contact to the other end of the RED-BLUE STRIPE wire that was cut. Trigger the relay with a toggle switch of any kind. Get 12v from a source that turns off with the ignition.
EXPLANATION:
One of the standard VSC OFF mods is to “trick the truck” into thinking the center diff is locked when it really isn’t. As the truck will turn off VSC when the center diff is locked this disables VSC. However the center diff lock light illuminates as well. This is because the RED-BLUE STRIPE wire that is directed to ground by the mod connects to an input on both the 4WD ECU and SKID CONTROL ECU. The 4WD ECU then indicates to the instrument cluster (Combination Meter on the schematics) that the Center diff is locked. To prevent this while still indicating to the SKID CONTROL ECU that the diff is locked we need to add a relay that leaves the wiring as OEM when the mod is off but connects ONLY the SKID CONTROL ECU EX1 to ground when the mod is on. This separates the SKID CONTROL ECU from the center diff lock sensor when the mod is on and signals it that the center diff lock is on thus it turns VSC off. However, the instrument cluster lamp for the center diff lock is activated by the 4WD ECU NOT the SKID CONTROL ECU. Thus by leaving the wiring intact from the 4WD ECU to the center diff lock sensor the indicator lamp displays the actual state of the center diff at all times. Additionally the mod will retain its state through restarts of the engine and will not interfere with ECU self checks on startup.
Here we see the interconnection between the center diff lock sensor and the 4WD ECU. When the center diff is locked the CDL output is connected to ground.
Here we see the connection between the Skid Control ECU the 4WD ECU and the center diff lock sensor. You can see the split between the three ECUs at J28.
Below you can see the connection between the Skid control ECU and the Instrument cluster. Only VSC indication is present.
Here you can see the connection between the 4WD ECU and the instrument cluster. Only the 4WD ECU controls the center diff locked light.
Below is a schematic for the mod.
I don’t believe this has been done before. If it has, please link it. I’ll complete an install in a few days and will report back.