If your car engine light comes on and the OBD codes are P0330 (#2 knock sensor) or P0325 (#1 knock sensor), this indicates a bad knock sensor. It is more common for knock sensor #2 to fail. It is also more common for the wire harness to go bad instead of the knock sensor itself. It is rarer for both knock sensors to go bad at the same time but this can happen. With a bad knock sensor, you may experience less power and intermittent loss of overdrive/4th gear. Here are some options to overcome this problem:

A). Drive up to 60 - 70 miles per hour on a straight portion of clear freeway (there are YouTube videos on this). This will run your engine at about 4000 rpm. Put transmission in neutral, shut off engine, count to 3, turn engine back on while car is still rolling straight along the freeway, put transmission back into drive, and transmission should shift into overdrive/4th gear. This should only be done if you can do it safely but there are inherent risks such as possible loss of control, especially if freeway surface is wet. Very dangerous. DO NOT do this on a curve in the road because sometimes the steering wheel will lock in position when you turn engine off. Even more dangerous. Do this at your own risk.
B). Spend $1500 at a mechanic to replace both knock sensors and wire harnesses. This is an 8 hour job for a professional. DIYers will take longer.
C). Purchase replacement knock sensors and mount them on a metal bracket mounted to the engine block to properly ground the sensor. This will require drilling and tapping a hole to screw the new knock sensor into. If engine light does not go off, this is because the electrical grounding is not adequate so find another location to mount the replacement knock sensor. This will avoid the $1500 repair bill but will not fix the sensors. The engine light will turn off, engine and transmission will work as normal, and car will probably pass smog test (but I have not confirmed this).
D). Find the 2 wires which connect the sensors to the Engine Control Unit under the glove box and jumper the 2 wires together (no wire cutting required). This will only work if one knock sensor is bad but the other is good. This will not work if both sensors are bad. This will avoid the $1500 repair bill but will not fix the sensors. The engine light will turn off, engine and transmission will work as normal, and car will probably pass smog test (but I have not confirmed this). The following steps describe this option.

This is for a California year 2000 ES300 first sold in December 2000:

1). Remove the glove box. There are 3 Phillips screws along the inside top edge of the glove box which are visible with glove box door open. There is a Phillips screw at the bottom left and a 10mm hex screw at bottom right (this hex screw is only visible after pulling back the plastic molding at that corner).
2). The Engine Control Unit (ECU) is sitting vertical with multiple white plastic electrical connectors attached at the front of the ECU itself. The white plastic connector you need to unplug from the ECU is the very bottom connector. See green pointer in photo. You may first need to unplug the connector directly above the bottom connector to give you adequate space to unplug the bottom connector.
3). The 2 knock sensor wires are in the middle toward one edge of the connector. See photo. The wires are slightly thicker than the rest of the wires and the wires are clear-colored. One wire has a red piece of tape on it to identify it as the wire for knock sensor #2. See photo. The other wire is for knock sensor #1 (this info is based on online Lexus forum threads by other ECU hack jobs done in the past). This info can also be determined by locating the knock sensor wire harness in the engine bay and looking at the wire colors in the harness and looking for the same colored wires at the Engine Control Unit.
4). Remove about 3/8 inch length of clear plastic sheath on both wires as shown in photo. Use a craft blade. Be careful not to cut into the metal wire strands in the middle of the wire. As I was rushing to finish the job, I accidentally cut a few metal wire strands but this was not enough damage to negatively affect the final outcome of this repair job. Thank You Lord. Note: No wire cutting is required.
5). Fabricate a jumper using a standard red crimp connector. Obtain a standard red or blue crimp style electrical connector as shown. Trim it using a large wire cutter similar to the one shown in photo. Trimming will help to keep the jumper size small and short which is better since the wires are in a tight space and slightly curled.
6). Run the 2 wires along each side of the jumper and use regular pliers to mildly crimp each side to clamp each wire. See photo of jumper in place. Do not overcrimp which is unnecessary and can deform the jumper.
7). Cover the jumper with black electrical tape as shown.
8). Test run the car.
9). Replace glove box.
May God give you success in your ECU hack repair job and save you a bunch of $$$

Notes:
a). A wire jumper and solder can be used in place of the jumper described above. A wire splice connector should not be used because it is considered appropriate only for low vibration conditions (motor vehicles are considered high vibration conditions) and may loosen over time.
b). Some ECU hack jobs on YouTube show the bad knock sensor wire is cut first. Then the 2 wires coming from the white plastic connector are connected to the 1 good knock sensor wire coming from the engine bay. This option also works but it requires you to correctly identify which wire to cut. This is an unnecessary risk. If you jumper both wires together (as shown above) WITHOUT CUTTING either wire, this removes the risk of making a mistake in identifying which wire is the good sensor and which wire is the bad sensor. Why cut the bad wire if no power is in that wire anyway? Keep it simple: don't cut any wires and just jumper both wires together.
c) For those concerned about driving with a nonfunctioning knock sensor, some options are: Use higher octane fuel, use the throttle more carefully and less aggressively. I have driven various cars with occasional knocking for many many years, and no significant engine damage was noted. I suspect engines, in general, are very tolerant to knocking and 99.9% of engines will eventually fail due to other problems and not because of knocking.


Green pointer is pointing to the white plastic connector slot at the very bottom of the Engine Control Unit (ECU). This is the connector which contains the knock sensor wires and so this connector needs to be disconnected from the Engine Control Unit to perform the work on the wires. The Engine Control Unit is the metal enclosure with the "CM" sticker attached to it at the top. It has a large circuit board inside.
Note: Some Toyota ECU circuit boards have lettering (KNK1 and KNK2) on it denoting which solder connections on the circuit board are the knock sensor connections but on this particular circuit board, there was no such lettering so I put the ECU cover back on and put the ECU back in its original position under the glove box.




This photo shows the 2 clear colored knock sensor wires next to each other. The photo shows I removed approximately 3/8 inch of clear plastic insulation exposing the bare metal wire strands using a craft blade/razor blade. Now the wires are prepped for jumping them together. Notice the red tape on one of the clear colored wires - this is the #2 knock sensor wire. The other clear colored wire is the #1 knock sensor wire according to online research on this topic.





This is the standard red electrical crimp connector I used to make a jumper. The pen tip is pointing to the jumper which was made by modifying the red crimp connector. After trimming the red crimp connector with a large wire cutter (also shown in photo), I widened the curled edges slightly with round-ended pliers (also shown in photo) to make the jumper easier for the wires to slide into place before mildly crimping the wires in place with a regular plier.




This photo shows the jumper in place after mildly crimping both sides to keep the wires from moving out of place. Do not over-crimp to the point of severely deforming the jumper.




This photo shows black electrical tape covering the jumper. Now, the white plastic connector is ready to be put back into its original position attached to the Engine Control Unit. As you push the white plastic connector back into the Engine Control Unit into the bottom connector slot where it originally came from, make sure you hear a 'click' which tells us the connector is fully in-place.