DTC 27 ODS Communication Error

WARNING: This page is about a different car, the 2006 Subaru Outback and 2006 Subaru Legacy. However, it is still accessible from the selected car via links, so may be relevant.

DTC DETECTING CONDITION:

Communication to the occupant detection control module is faulty.
Airbag rear harness circuit is open, shorted, shorted to ground or shorted to power supply.
Occupant detection harness (seat harness) is faulty.
Occupant detection system is faulty.
Airbag control module is faulty.

DIAGNOSTIC PROCEDURE CHART

Step	Check	Yes	No
1 CHECK POOR CONTACT IN CONNECTORS. Check for poor contact of the connectors between the airbag control module and the occupant detection control module.	Is there poor contact?	Reconnect the connector. If defective is not improved, replace the airbag rear harness RH or the occupant detection harness (seat harness).	Go to step 2.
2 CHECK AIRBAG HARNESS. Turn the ignition switch to OFF, disconnect the battery ground cable, and wait more than 20 seconds. Disconnect the connector (AB18) from airbag control module. Disconnect the connectors (AB59) and (AB61) under the passenger's seat. Connect the connector (1U) in the test harness U to connector (AB18). Connect the connector (1AB) in the test harness AB to the connector (AB61). Measure the resistance between connector (3U) in the test harness U and connector (2AB) in the test harness AB. Connector & terminal (3U) No. 2 - (2AB) No. 1: (3U) No. 4 - (2AB) No. 2:	Is the resistance less than 10 Ω?	Go to step 3.	Replace the airbag rear harness RH along with body harness.
3 CHECK AIRBAG HARNESS. Measure the resistance between connector (3U) in the test harness U and chassis ground. Connector & terminal (3U) No. 2 - Chassis ground: (3U) No. 2 - (3U) No.4:	Is the resistance less than 10 Ω?	Go to step 4.	Replace the airbag rear harness RH along with the body harness.
4 CHECK AIRBAG HARNESS. Turn the ignition switch to ON. Measure the voltage between connector (2AB) in the test harness AB and chassis ground. Connector & terminal (2AB) No. 3 - chassis ground:	Is the voltage more than 9 V?	Go to step 5.	Check the battery voltage and fuse. If there is no faulty, replace the airbag rear harness RH along with body harness.
5 CHECK AIRBAG HARNESS. Measure the voltage between connector (2AB) in the test harness AB and chassis ground. Connector & terminal (2AB) No. 1 - chassis ground:	Is the voltage more than 9 V?	Replace the airbag rear harness RH along with body harness.	Replace the occupant detection harness (seat harness). If defective is not improved, replace the occupant detection system (seat cushion & frame assembly), and then the airbag control module in this order.