Code 1-3-1 (Ignition System RPM Signal)

Turn ignition off. Disconnect fuel system ECU connector and remove protective sleeve. Connect a voltmeter between harness side of terminal No. 1 (Brown wire on 240; Yellow/Gray wire on 740/940) and ground. Run starter motor. Voltage reading should be 5-7 volts. If reading is not 5-7 volts, check wiring between ignition ECU and fuel injection ECU. If wiring is okay, replace ignition ECU.