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DISCLAIMER:
Try this modification at your own risk. I am not responsible for any personal injury/death, mistakes/long term effects and/or damage to property.
The procedure posted here is based solely on my experience with my 2001 ES300. Wiring and connectors can vary widely between models and years so always verify your car before making any connections.

The steps shown here are not to replace the installation/User Manual that comes with the TPMS system. They are only to help installing the system on the ‘01 ES300. I highly recommend reading and following the instructions in the manual.

Disconnect the negative battery terminal before working on the electrical system of the car. Ensure that you make good wire connections and that the wiring harness/antenna are routed and fixed in good position.

(Please ignore the winter condition of the car, I didn’t clean it for few weeks now )

I installed the Hella-TC400 Tire Pressure/Temperature Monitoring System and thought to post how-to-do it here:

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First, note the main components of the system:

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STEPS:
1) INSTALLING THE SENSORS:
The sensors need to be installed by a professional tire service shop. Make sure they are installed properly according to markings on the sensors (LF: Left Front, LR: Left Rear, RF: Right Front, RR: Right Rear). Take the manual with you to the shop and show them the steps of installing the sensors. Don’t forget you need new wheel balancing after the sensors are installed.

I found these very informative links from tirerack.com:

http://www.tirerack.com/tires/tirete....jsp?techid=44
http://www.tirerack.com/tires/tirete...jsp?techid=152

If you follow all instructions carefully, it is very simple and easy to install the sensors.

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2) MOUNTING THE RECEIVER MODULE:
You can mount the receiver module anywhere as long as you can have good signal with no interference. The module has 3 connectors: the LCD display wire connector, an antenna connector, and finally the power connector. The first two connectors are simple plug and play, while you need to make sure how to connect the power wire carefully (will talk about this in the wiring section below).

For mounting the module I made a custom plate and L-brackets as in the pic and mounted the module just under the lower instrument panel. I found there is an excellent signal with no interference in this place. I plugged the antenna wire and fixed it with cable tie just above the OBD II connector (you can try any place you like until you get good signal after install the system).

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Fixed with mounting L-brackets:

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Showing antenna wire:

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3) Mounting the LCD Display:
You can mount the LCD Display anywhere you like as long as you can hide the wire and see/read the information shown on the display; and also to be able to hear the warning tones from the LCD.

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Wire is hidden behind the panel:

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I routed the wire below the steering wheel to the receiver module and used cable ties to fix the wire to the panel. After routing the wire, you need to insert display wire into the 4-pins connector according to the color coding and plug it into the receiver module.

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4) Wiring the power wire harness:

The power harness has 3 wires that are color coded as follow:
- Red wire for constant 12V power source. The system comes with an inline
5A fuse that should be connected to this wire.
- Orange wire for switched (ignition) 12V power.
- Black wire for ground.

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After reading in the ES300 Repair Manual I found that the ES300 has a wire harness for cellular mobile telephone that is not used in my car. Luckily it has 5A fuse (in the engine compartment fuse box).

This wire has a constant 12V so I used it as a constant power source and connected this wire to the red wire that goes into the TPMS receiver module.

(Pic taken from the ES300 repair manual – Edited)

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To get access to this wire you will have to remove the lower cowl side trim as follow:

(1) Remove the black (size 10 or 12) plastic clip. (2) Then pull the lower front door scuff inside plate to the outside slightly, (3) and then remove the cowl side trim.

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Locate the connector as shown in the pic.

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Another pic.

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The telephone wire is the green-black wire. I used a terminal removing tool to remove the wire from the connector (or you can use a small flat screwdriver). To remove the wire you have to disengage the locking mechanism of the connector (Terminal Retainer) and then insert the tool as shown in the pic and push the terminal retainer up then pull the wire (Be careful not to damage the terminal/connector when attempting this step).