DIY - Bypassing Tire Pressure Warning System (TPWS / TPMS)

[CTScott]

Note: Please jump to page 3, post #45. The first pass of a solution on pages 1-3 ended up not working.

For the simple method, please jump to post 115. This method does not require resistors.

http://www.yarisworld.com/forums/sho...&postcount=115


Following is a DIY to disable the system, without causing the TPWS light or MIL (malfunction indicator light {or check engine light, as some like to call it}) to light.

A while back there was a thread about the issues with either using rims which are not compatible with the tire pressure sensors or running two sets of rims. The Yaris TPWS can only be programmed to respond to one set of four sensors. To switch to a second set, you would have to bring your car to the dealer to have the TPWS reprogrammed for the second set (This is typically about a $90 charge).

I did a bit of reverse engineering on the TPWS and believed that I found a soultion. Linny recently tried this solution and verified that after more than 100 miles of driving there were no issues.


Procedure :
(WARNING: Modifying anything on the Yaris is done at your own risk!!!)


The TPMS ECU is located behind the lower passenger glove box:




The TPWS system will only report an issue with not hearing from the sensors if for 15 minutes it doesn't hear from a sensor while the vehicle speed is 5 MPH or greater and the Engine speed is 1000 RPM or more.

To keep the system from reporting an error, do the following:

1. Start without an error: If you start with the system in the error free state (by starting the vehicle and having the 4 tires with the sensors next to the vehicle (or mounted on it) and ensure that the TPWS light is not lit or flashing.

2. Shut the engine off.

3. Pull out the lower passenger glove box and locate the TPWS ECU (to the right, just above the fan assembly):



3. Clip and cap both ends of the VSS and ESS wires to the TPWS ECU. Leave a couple of inches on the connector side so that you can resplice if you wish to re-enable the system. The connector is shown below. The VSS wire is the Violet one and the ESS wire is the red one, two pins after the violet one. Also, if you wish to switch between a set of rims with sensors and a set without, you can add a DPST (dual pole, single throw) switch to disconnect / reconnect both wires as desired to disable/enable the TPWS.



For adding the switch the following is a good choice:



http://search.digikey.com/scripts/Dk...?name=CH867-ND

To wire the switch, connect the cut wires to the sets of terminals on either side of the switch as follows:

Red - - Red
Vio - - Vio


Someone posted a DIY of disabling the feed to the light (the brown wire on the connector above, if you were wondering). The problem with just clipping this wire is that the DTCs will still be logged and may result in your Malfunction Indicator Light coming on.