The PO500 code is for the P0500 TOYOTA - Vehicle Speed Sensor 'A'. This is not a code for an ABS issue. That code has nothing to do with brakes or ABS.
Edit, I take that back as some of the 2003 use the wheel sensors as the speed sensor. That is what I ran across digging on the web. The "P" series of codes are power train codes and the "C" series of codes are for chassis, which includes the ABS system. You need a reader that does ABS to pull the "C" codes for the ABS. When I seen the P code, I know it was not an ABS code. I am sorry about that. What gets strange is that 2003 automatic transmissions all have a speed sensor but with the manual transmissions, some may have a speed sensor and some may not. The ones that do not have the speed sensor are kind of left out in wonder land because the information is not clear.
If you have a speed sensor on your transmission bell housing then you need to check that sensor which is different then the wheel sensors. Here is link for P0500 code testing:
http://madstyle1972.com/Repair/05/200o8c04/cip0500.pdf
If you do not have a speed sensor on your transmission then you need to test the wheel sensors and you should also get "C" codes from an ABS code reader to help find the problem. Here is a link for that:
http://madstyle1972.com/Repair/05/2011i/cic02003.pdf
Here is an link and read the link to see the confusion about the sensors.
http://matrixowners.com/index.php?/topi ... t-come-on/
You will probably run into conflicting information on this because of the "odd duck" of being with or without a true speed sensor.
Here is another read:
http://matrixowners.com/index.php?/topi ... cel-p0500/
Combination Meter :
http://www.toyota-4runner.org/3rd-gen-t ... meter.html