[Tamaki]

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.

[PNWLivin]

I've been looking for a new method of achieving this that's similar to the one mod that was on this board a few years ago. A guy made a little electrical board to connect and made everything operate OEM like with an OEM switch. Keep us updated once you try this out. Do you plan on connecting an OEM traction control switch to this?

[Tamaki]

Unfortunately no luck. The skid control ECU goes into error mode if the signal from the diff lock is grounded without also grounding the 4wd computer as well.

After looking at a the diagrams I noticed that the green/red stripe wire for the diff lock light from the 4wd ecu runs to the skid control ECU through a junction block. While this is probably to prevent a situation where the diff is still locked but VSC is turned back on, there must also be checks happening to verify that the diff indicator is lit before disabling the VSC. If you watch closely when locking the diff you'll see a delay between the diff lock light coming on and VSC turning off.

I'd like to know how Kliv was handling this with only 4 wires on his board.

[Tamaki]

I was going to use this switch. Amazon.com: CH4X4 Push Switch for Toyota - VSC Symbol - Amber Led : Automotive
It's a toggle switch not momentary like OEM. A word of warning. The switch will need to be disassembled and resistor R3 removed. It causes an error if used for the standard VSC off mod as the internal circuit allows for current to feed back to the ECUs.

[Drcoffee]

I used the method which adds a momentary switch into the yaw sensor wire. It shuts down all of the nanny state devices, abs, skid control, vsc,, etc. none of these systems work well enough for me to trust them with my life. A driver can only compensate for loss of traction events when they are not fighting the nanny state crap.

Committing to enter traffic on wet roads can turn horrifying when the ecu decides you dont need power to accelerate and cuts power and adds brakes. Been there, done that twice. All you can do is Sheet your pants. Turning off everything lets me be in control.

[Bluesky 07]

Originally Posted by Drcoffee

I used the method which adds a momentary switch into the yaw sensor wire. It shuts down all of the nanny state devices, abs, skid control, vsc,, etc. none of these systems work well enough for me to trust them with my life. A driver can only compensate for loss of traction events when they are not fighting the nanny state crap.

Committing to enter traffic on wet roads can turn horrifying when the ecu decides you dont need power to accelerate and cuts power and adds brakes. Been there, done that twice. All you can do is Sheet your pants. Turning off everything lets me be in control.

I see your point but no ABS would be a deal-breaker for that setup.

[PNWLivin]

Originally Posted by Tamaki

Unfortunately no luck. The skid control ECU goes into error mode if the signal from the diff lock is grounded without also grounding the 4wd computer as well.

After looking at a the diagrams I noticed that the green/red stripe wire for the diff lock light from the 4wd ecu runs to the skid control ECU through a junction block. While this is probably to prevent a situation where the diff is still locked but VSC is turned back on, there must also be checks happening to verify that the diff indicator is lit before disabling the VSC. If you watch closely when locking the diff you'll see a delay between the diff lock light coming on and VSC turning off.

I'd like to know how Kliv was handling this with only 4 wires on his board.

I'm pretty sure I saw wiring diagrams from Kliv on here.

[LOSTR4]

New fine-grained VSC OFF Mod for V6 1GR

[Drcoffee]

Originally Posted by Bluesky 07

I see your point but no ABS would be a deal-breaker for that setup.

In a newer vehicle, ABS is much better than in older ones. But in my truck, its just not that effective. The pulse is just too slow to actually work as promoted. I would be okay with turning the ABS off permanently but then I would have the light on constantly. Plus the liability once I sell it.