Sea.Jay

guys i need some real help.

2002 4runner, 2WD. auto

there is a factory trac off switch to the left of my steering wheel. thing is it turns off by itself when i hit 10-15 mph


can i do the andymod anyways or am i just out of luck?

GSGALLANT

It's normal for your VSC to re-enable itself at a certain speed. Just unplug the pressure sensor on the master cylinder while your engine is running (see picture on page 15 of this thread). If the Andymod is going to work for you, unplugging this sensor will give you the VSC/TRAC/ABS lights, and the systems will be disabled while that sensor is unplugged.

Plug that sensor connector back in, shut the truck off, start it back up, and the lights should all be off again with the systems functional. If that works, you should be good to go to wire in the switch for the Andymod.

02_Limited

What about implementing the TRAC OFF button that 2WD models have? Does that have to do with the ECU?

fasthorse67

That has been tried to no avail. I looked at the TB today and I don't think swapping in an older one will work. You would lose cruise control and trans. kick down at the very least. The cable you see is the throttle cable everything else is controlled by servos and wires. Actually I belive the throttle is controlled by a servo also it's just contained in the TB. It looks to me like the throttle cable acts on a reostat which in turn controls a servo for the TB valve. I'm going to keep digging and figure this out!! There has to be a better way!!

GSGALLANT

Here's a bit of info to help you. The lever that the throttle cable pulls on at the throttle body is the input to the accelerator pedal position sensor (located on the TB). With the truck running, the signal from that sensor is an input to the throttle control motor (via the ecu, of course). Based on the current position of the throttle plate (which the ecu gets from the output of the throttle position sensor), and the throttle demand (supplied by the accelerator pedal position sensor), the ecu determines the required position for the throttle plate, and controls the throttle control motor accordingly. The throttle control motor is what moves the throttle plate.

If any of these electronic components fail, the truck goes into "limp mode" in which case the throttle cable is the only thing that moves the throttle plate; however, the most the throttle plate can open in this situation is approx 1/4 of the way open. It's a fail safe to allow one to get his truck home or to the dealer if any of the fancy electronics fail.

Sea.Jay

so theres nothing available for 2wd? I have a 2002 4runner sr5 2wd with the factory trac off button. can i do anything?

- chris

fasthorse67

I wonder if there is some way to mechanically link the cable and plate for all of its travle instead of just 1/4. Does the position sensor control anything else on the engine? Such as fuel curve or ignition.

GSGALLANT

The ECM uses throttle valve position information to determine/control:

1. Engine mode: idle, part throttle, or wide open throttle.
2. When to switch off AC and emission controls at Wide Open Throttle (WOT).
3. Air-fuel ratio correction.
4. Power increase correction.
5. Fuel cut control.

surf4runner

ECU - when the chuck engine light is on the TRAC/VSC is disabled, ABS still functions.

maybe thats the circuit for the signal to disable it???


yes.
i just disconnect @ the MC when off road. didnt feel like wiring a switch in.

fasthorse67

I was affraid of that. Okay, I guess I can forget about getting rid of Drive by Wire. I'm going to stop at a dealer this week and see if I can get schematics for the center diff. lock. Maybe we can get somewhere that way.

02_Limited

Props to you fasthorse for being persistent about this:

bigtrucknwheels

too bad you aren't in PA... The tech school that I attended (still good friends with all the staff there) has a mega-reader/writer. they can program your ECU to do ANYTHING haha. my friend tweaked his cavalier all the time when he went to school there.

BUT, just to warn you, modifying your ECU is grand and dandy, but as soon as it looses power, it returns to stock configuration...

02_Limited

What part of PA are we talking about? I'd be willing to drive somewhere (besides the dealership) to get this "problem" fixed. I wonder if the dealer would be willing to do anything about it. I'm sure they can screw with the TRAC settings somehow. If they provided the equipment to mess with the ECU settings (in hopes of disabling TRAC), but don't actually do the work/tweaking, would they still be liable if something went wrong? Where I normally take my truck, I have made good connections with a few of the service team members and mechanics