Code 3-1-2 (Knock/Fuel Enrichment Signal Missing)

Turn ignition on. Connect a voltmeter between terminal No. 28 (Brown/White wire on 240; Gray/Red wire on 740/940) of fuel system ECU connector and ground. Reading should be approximately 0.7 volt. If voltage is not specified, check resistance between appropriate ECU connector wire and knock sensor. For knock sensor testing, see procedures in SYSTEM/COMPONENT TESTS article in the ENGINE PERFORMANCE Section.