When not using hand-held tester:

WARNING: This page is about a different car, the 2004 Lexus GS 430 and 2004 Lexus GS 300. However, it is still accessible from the selected car via links, so may be relevant.

Check ENGINE TROUBLESHOOTING DTC P0500: VEHICLE SPEED SENSOR "A" .
1. OK: Replace combination meter.
2. NG: Go to Next Step.
Check harness and connector between combination meter and ABS ECU (See O/D DIRECT CLUTCH SPEED SENSOR ).
1. NG: Repair or replace harness or connector.
2. OK: Go to next step.
  Check speed sensor circuit and ABS ECU. (See PRE-CHECK , PRE-CHECK )