Tire pressure sensors

[Tink1]

No options to rid ourselves of the annoyance tht you know of?

[CTScott]

Originally Posted by Tink1

No options to rid ourselves of the annoyance tht you know of?

Last night I got the 09 Service Manual, which has the section on the TPWS, which the 07 manual lacks. I have verified as well that the 08 matches the 09. The TPMS ECU is located behind the lower passenger glove box:



System operation:

The system primarily listens for the sensors to squawk (which happens every couple of minutes for each sensor {yeah, not really real time, hence calling it a Tire Pressure Warning System rather than monitoring system}). It can also send a 125Khz signal to force the sensors to report (and it does so once when the car is started). To know that it should be hearing from the tires (and to initially know that the car has gone from doing nothing to running) it is fed two signals: From the combination meter - Vehicle speed (Speedometer) and from the ECM - Engine speed (tach).

Errors:

TPWS light on solid indicates a low or high pressure in one of the 4 tires (by the way, our spare is not outfitted with a sensor, like on other vehicles).

Blinking for 1 minute indicates a malfunction with the system (not low or high pressure from a sensor) and a DTC will be logged.

When no transmitter ID is received from a tire pressure warning valve and transmitter for a total of 20 minutes while the vehicle speed is more than 8 km/h (5 mph) or no transmitter ID is received from all the tire pressure warning valves and transmitters for a total of 20 minutes, DTCs are set.


The logged DTC's can be:

C2181 (xmit ID1 not received)
C2182 (xmit ID2 not received)
C2183 (xmit ID3 not received)
C2184 (xmit ID4 not received)
C2181 (VSS error)
C2181 (Engine Speed Sensor Error)



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

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, I belive that you can 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.




Someone posted a DIY B.H. 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.