Possible Causes

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

Malfunction in IG1 or B+ signal circuit of keyless control module caused by:

Keyless control module malfunction.
Faulty METER fuse (10-amp) or ROOM fuse (10-amp).
Open circuit in wiring between either fuse and keyless control module.

Malfunction in keyless control module door open/closed signal circuit caused by:

Door switch system malfunction.
Keyless control module malfunction.
Open or short circuit in wiring between keyless control module and door switch.

Malfunction in keyless control module GND signal circuit or malfunction in IG1 or B+ signal circuit of theft deterrent control module caused by:

Theft deterrent control module malfunction.
Faulty ENGINE fuse (10-amp) or ROOM fuse (10-amp).
Open circuit in wiring between either fuse and theft deterrent control module.
Open circuit in wiring between ground and theft deterrent control module.
Open circuit in wiring between keyless control module and theft deterrent control module.