Inspection Procedure

1. Disconnect the M4 ECU connector.
2. Disconnect the S23 amplifier connector.
   Fig 1: Identifying S23 Amplifier Connector Terminals

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
3. Measure the resistance of the wire harness side connectors.

   Standard resistance 

   TESTER CONNECTION SPECIFIED CONDITION CHART
   
   

   Tester Connection	Specified Condition
   N4-5 (TX+) - S23-5 (MTX+)	Below 1 Ω
   N4-10 (TX-) - S23-18 (MTX-)	Below 1 Ω
   N4-5 (TX+) - Body ground	10 kΩ or higher
   N4-10 (TX-) - Body ground	10 kΩ or higher

NG: REPAIR OR REPLACE HARNESS AND CONNECTOR 

OK: PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS TABLE OR DIAGNOSTIC TROUBLE CODE CHART