Circuit Description

WARNING: This page is about a different car, the 2002 Lexus RX 300. However, it is still accessible from the selected car via links, so may be relevant.

The headlight relay will be ON by operating the headlight switch. The transistor which activates the taillight relay has 2 sorts:

One activates directly by the headlight switch for fail safe.
The other activates by ECU.

The one that activates by ECU has 2 systems and prevents the headlight from turning off at the time of one system trouble in the automatic operation circuit. See Fig 1.

Fig 1: Identifying Headlight Relay Circuit