Power Transistor
WARNING: This page is about a different car, the 2000 Infiniti Q45 and 2000 Infiniti G20. However, it is still accessible from the selected car via links, so may be relevant.
Faults in power transistor should set a DTC P1320. For testing procedure, refer to DTC P1320: IGNITION SIGNAL under DIAGNOSTIC TESTS in appropriate SELF-DIAGNOSTICS article.