Originally Posted by toyomoho (Post 87518)

The name integration is termed because the relay integrates with more then one system. Like door locks, remote door lock, key/seat belt reminder, interior lights and moon roof.

The integration relay incorporates diodes, resistors, transistors and relays soldered to a circuit board. Toyota provides no service data or detailed schematic of the relay. This makes repairs difficult, most owners replace the relay if a problem.

What can cause a problem? The unit appears not to generally fail on its own but this is possible. Bad component, solder joint, etc. Other causes can be incorrect installation of remote door lock and alarm. Poor regrounding of wiring after chassis repairs, failing to disconnect battery when doing electrical work and jump starting engine with electrical components turned on.

As to what to do:

The interior lights receive power from the Dome fuse. This power goes first to the integration relay. Then via an incorporated bus to the vanity lights (do these work?) and Dome light. As you know, this light is always powered. The Dome switch connects the ground of the bulb socket to open, ground or the wiring going to the integration relay.

The wiring circuit going to the relay depends on if the dome light is "fade out" or not. Fade out is the light stays on, then turns off by itself.

If no fade out the wiring goes via another integration relay bus to the rear door switches. The door switches are normally open when door is closed (does the light work if rear doors are open).

The wiring to the front door switch wiring is more complicated routing through a diode before going to the switch. The diode isolates other attached circuits.

The fade out wiring incorporates into the integration relay circuitry. Alas the circuit diagram provided is not complete.

Might check the integration relay ground wire (white/black). The wire goes first to a splice box then ground, both located on the drivers side of the dash console.

Make sure the dome light has full battery voltage.

Where is the car located or originated from? The integration relay part number appears less common then others for same car and year.