Possible Causes

WARNING: This page is about a different car, the 2005 Mazda Tribute. However, it is still accessible from the selected car via links, so may be relevant.

ISO 9141 network circuit (LB/W) shorted to ground or open
DLC D-01
RCM 0810-101
RCM

RESTRAINT CONTROL MODULE (RCM) DOES NOT RESPOND TO DIAGNOSTIC TOOL - DIAGNOSTIC PROCEDURE

PINPOINT TEST 2		THE RESTRAINT CONTROL MODULE (RCM) DOES NOT RESPOND TO THE DIAGNOSTIC TOOL
STEP	INSPECTION		ACTION
1	CHECK THE ISO CIRCUIT BETWEEN THE RCM AND THE DLC FOR AN OPEN Key OFF. Deactivate the air bag system. See OCCUPANT RESTRAINT SYSTEM . Disconnect the RCM 0810-101. Measure the resistance between the RCM 0810-101 pin 11, circuit (LB/W), harness side and the DLC D-01 pin 7, circuit (LB/W), harness side. Is the resistance less than 5 ohms?	Yes	GO to next step.
1		No	REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test. CARRY OUT the data link diagnostics test.
2	CHECK FOR CORRECT RCM OPERATION Disconnect all the RCM connectors. Check for: corrosion pushed-out pins Connect all the RCM connectors and make sure they seat correctly. See OCCUPANT RESTRAINT SYSTEM . Operate the system and verify the concern is still present. Is the concern still present?	Yes	DIAGNOSE the ISO 9141 communication network. See PINPOINT TEST 5: NO INTERNATIONAL STANDARDS ORGANIZATION (ISO) 9141 NETWORK COMMUNICATION .
2		No	The system is operating correctly at this time. Concern may have been caused by a loose or corroded connector. CLEAR the DTCs. REPEAT the self-test. CARRY OUT the data link diagnostics test.
Courtesy of MAZDA MOTORS CORP.