TPMS light bypass switch
 

This mod was inspired by rook who did the research in another thread here:
http://www.toyota-4runner.org/showth...threadid=38010

I get the blinking TPMS dash light (LED) when I run winter steel wheels without sensors. This switch is a cheap alternative (less than 5 Canadian bucks) that will defeat the light. You can also use it if you run other wheels without the TPMS's or if you get a system fault that is big $$$ to fix.

The default electrical principal behind the system is that it fails safe. The default condition is that the LED is lit using a ground path in the gauge cluster. The ECU closes a circuit and creates a ground path to bypass the LED when the ignition is on and everything is OK with the system. The ECU opens this circuit to turn the light on (fully open when it senses low tire pressure creates a steady light on; cycling open/closed when it senses a system fault creates a blinking light.) Merely unpluging the ECU to bypass the system disables the ECU but actually creates a steady on LED.

This switch installation provides another path to ground to bypass the ECU ground. It is easy to get to the location behind the lower panel under the glove box.

The research shows that this principal probably changed in '07 and later so this mod may not apply to later 4th Gen's.

Here is the stock wiring diagram for the '04:

Start by removing one screw (see later picture) and removing the trim panel under the glove box by pulling toward you along the top. It's held in by 3 (yellow) clips and 2 foam pads along the bottom. The red arrow points to the TPMS ECU and connector. The green arrow points to where I opened up the yellow wiring harness to do the splice on the indicator light wire (postion 6 on connector T16.)

Closeup of the splice in the pink-black wire:

Overview of the area with the switch (red arrow), taped up splice (green arrow) and new ground point (blue arrow; used an extra nut on an existing bolt):

Closeup of the simple 2-pole rocker switch:

Final location of the switch stuffed loosely next to the air vent (red arrow). Green arrow points to the screw you initailly need to take out to remove the panel.

Simple and it works.

Re: TPMS light bypass switch
 

My light comes on when the tires are cold and goes out after about a mile of driving or just enough to heat up the tires. This looks useful as sometimes it just stays on when it's too cold. Thanks for the mod.:cheers:

Re: Re: TPMS light bypass switch
 

Your pressures are right at the signal threshold. I wouldn't suggest you disable the LED if all you have is a steady "on" light due to low tire pressure. That is what the system is designed to do. Just fill all 5 tires to 32 psi (or more.)

nice!
 

great writeup... hopefully this will help a lot of other owners who run a separeate set of wheels and tires for the winter

Great write-up! I was planning on doing something similar when the batteries die in my TPM sensors. I've heard they are good for about 7 years and are not replaceable! You have to buy new ones when the batteries die, and then have them programmed by the dealer! What a bunch of crap. I check my tire pressure regularly, so I don't really find much value in having the TPMS.

Instead of a switch, I'll just permanently ground the wire to keep the light off for good.

You don't say what year your T4R is. This may not work for you if you have a later model 4th Gen (I think it changed for '07 MY.) Check the link at the start of this thread and the other links referenced.

Hey Kmvreter, I would love to do this mod for my 06 SE but have a question, in the original thread mike508 talks of burning out a diode but there was no discussion about that, has anyone looked into the facts if this can occur or not?

Mine's an '04 but I believe the principal in the wiring diagram I attached up top also applies in '06. This mod completes an alternate path to ground that is reversible. I don't see how that can burn anything out.

Mine is an '04, so it will definitely work. I looked at the schematics long before you started this thread. I was planning on grounding that wire, but not until my TPMS batteries die.

BTW, what changed with the '07 and newer 4Runner? I'm sure that it would be just as easy to help those guys find a similar mod if we just had the schematics. I'd think it works of the same principal, no?

hmm, when i go back to the original post Mike508 says he verified for the 07 and 06 that he thought it worked because it burned out the diode due to a reduction of the impedance through the ECU which increased the voltage across the diode, maybe this is the case with the 06 and 07 but not with your 04. Has anyone with an 06 or newer attempted this mod?

thanks