For Using Hand-Held Tester

WARNING: This page is about a different car, the 2004 Toyota Corolla. However, it is still accessible from the selected car via links, so may be relevant.

Before using the tester, the tester's operator manual should be read thoroughly.
If the tester cannot communicate with the ECU controlled systems when you have connected the cable of tester to the DLC3, turned the ignition switch ON and operated the tester, there is a problem on the vehicle side or tester side.
1. If the communication is normal when the tester is connected to another vehicle, inspect the diagnosis data link line (Bus(+)line) or ECU power circuit of the vehicle.
2. If the communication is still impossible when the tester is connected to another vehicle, the problem is probably in the tester itself, so perform the Self Test procedures outlined in the Tester Operator's Manual.