You're correct in your suspicions Dave. This fault code is indeed for the particulate filter injector. Check the wiring and see what voltages you have. I don't have anything toyota specific but usually you would expect to see 2 wires, one at battery voltage and the other a switched earth. If you don't have battery voltage check the fuses, then wiring etc. If thats ok check for the switched earth from the ecu.

Diagnose the same as a normal injector really.