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Old 11-24-2008, 12:32 PM   #1
CTScott
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DIY - Bypassing Tire Pressure Warning System (TPWS / TPMS)

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.

Last edited by CTScott; 09-23-2009 at 01:57 PM. Reason: Point users to the working solution.
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Old 11-24-2008, 12:51 PM   #2
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very nice :)
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Old 11-24-2008, 01:03 PM   #3
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i will be doing this in the spring.thank you.
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Old 11-25-2008, 12:27 PM   #4
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Super DIY write up. Thank you CTS for the effort! I am planning to put vinter tyres on My Daughter's Yaris and was concerned about setting a code as she is due for Emissions and saftey inspection this november. The SW seem like a good idea. CTS You dont have to shunt any of the cut wires to keep an open antenna out of the ECU?

Does anyone know if the 14" steel rims sold through Tire rack or Discount Tire Direct will clear the calipers? Her car has optional 15 inch rims. I wish to put a 165-70 snows on the front to get better force/unit area (µN/cm2) at the contact patch.

Thank you for helping,

- Papa
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Old 11-25-2008, 12:34 PM   #5
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Quote:
Originally Posted by TheSilkySmooth View Post
Super DIY write up. Thank you CTS for the effort! I am planning to put vinter tyres on My Daughter's Yaris and was concerned about setting a code as she is due for Emissions and saftey inspection this november. The SW seem like a good idea. CTS You dont have to shunt any of the cut wires to keep an open antenna out of the ECU?

Does anyone know if the 14" steel rims sold through Tire rack or Discount Tire Direct will clear the calipers? Her car has optional 15 inch rims. I wish to put a 165-70 snows on the front to get better force/unit area (µN/cm2) at the contact patch.

Thank you for helping,

- Papa
14's should clear fine, stock brakes aren't huge.. +39 offset should work as well
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Old 11-25-2008, 12:36 PM   #6
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Quote:
Originally Posted by TheSilkySmooth View Post
Super DIY write up. Thank you CTS for the effort! I am planning to put vinter tyres on My Daughter's Yaris and was concerned about setting a code as she is due for Emissions and saftey inspection this november. The SW seem like a good idea. CTS You dont have to shunt any of the cut wires to keep an open antenna out of the ECU?

Does anyone know if the 14" steel rims sold through Tire rack or Discount Tire Direct will clear the calipers? Her car has optional 15 inch rims. I wish to put a 165-70 snows on the front to get better force/unit area (µN/cm2) at the contact patch.

Thank you for helping,

- Papa

No shunting is required. The two wires we are disconnecting are both 12 V analog signals which the ECU is pulling through A to D converters. We shouldn't be able to pick up enough noise to cause a false signal detection.
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Old 11-25-2008, 12:39 PM   #7
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Quote:
Originally Posted by CTScott View Post
No shunting is required. The two wires we are disconnecting are both 12 V analog signals which the ECU is pulling through A to D converters. We shouldn't be able to pick up enough noise to cause a false signal detection.
i thought speed and tach signals were both pulse signals.... ?
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Old 11-25-2008, 09:01 PM   #8
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Scott,
Insanely awesome thread! Thank you!!!....
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Old 11-25-2008, 09:20 PM   #9
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Man soooo killer. Installed trd/racing hart 18" and didn't have the sensors installed on them , Im so over the "warning" light on the dash . I'll be doing this this weekend .
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Old 11-26-2008, 04:02 PM   #10
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Thumbs up

The hardest part about this procedure was pulling the glove box out! Thanks CTSCOTT! I tried to get the service guy at our dealer to tell me how to disable the system and he wouldn't budge. He would just offer that what most people do is simply 'deal' with the light since most do not have the want or resources to drop $90 each time they want to switch rims/tires.
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Old 11-26-2008, 04:24 PM   #11
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very nice! i was just about to ask if there was a way to bypass it and then i saw this.
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Old 11-26-2008, 06:11 PM   #12
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okay...you guys lost me. Do you need to cut the wires or can you just leave it unplugged? Or are you just cutting the two wires?
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Old 11-26-2008, 09:56 PM   #13
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Quote:
Originally Posted by Ratboy View Post
okay...you guys lost me. Do you need to cut the wires or can you just leave it unplugged? Or are you just cutting the two wires?
You do need to keep the connector plugged in (with those two wires cut) to sucessfully do the mod. If you just unplug the connector, the TPWS light will immediately come on and will stay on until it is plugged back in.

Cutting those two wires fools the Tire Pressure Warning System into thinking that the car is not moving and the engine is not running. The TPWS will not report an error if it doesn't hear from the tire sensors as long as the car is not rolling and the engine is not running.
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Old 06-26-2021, 06:17 PM   #14
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TPWS issue

Quote:
Originally Posted by CTScott View Post
You do need to keep the connector plugged in (with those two wires cut) to sucessfully do the mod. If you just unplug the connector, the TPWS light will immediately come on and will stay on until it is plugged back in.

Cutting those two wires fools the Tire Pressure Warning System into thinking that the car is not moving and the engine is not running. The TPWS will not report an error if it doesn't hear from the tire sensors as long as the car is not rolling and the engine is not running.
We have the light on and are happy to just disable the system by cutting the wires. Someone said it only works if no light is on which is not the case here.
Can someone suggest a way to get the idiot light off AND disable the TPWS system please?
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Old 08-11-2021, 11:20 AM   #15
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Quote:
Originally Posted by Maui Paul View Post
We have the light on and are happy to just disable the system by cutting the wires. Someone said it only works if no light is on which is not the case here.
Can someone suggest a way to get the idiot light off AND disable the TPWS system please?
post #115 picture on the left will do it
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Old 11-26-2008, 07:42 PM   #16
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I cut the two wires as specified in the pictures provided by CTSCOTT. After cutting the wires I wrapped each of the ends from the two wires in electrical tape. I then plugged the connector back into the ECU unit and that is it!!
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Old 11-26-2008, 09:50 PM   #17
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Does this project also work for an 2008 3dr LB?
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Old 11-26-2008, 09:52 PM   #18
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Does this project also work for an 2008 3dr LB?
Yes. TPWS is identical on 2008 and 2009 3 and 5 door LBs and Sedans as well.
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