Diagnostic Aids

Normal "Scan" tester voltage varies between .1-1.0 volt while in "closed loop". Code 13 sets in about one minute if voltage remains between .35 and .55 volts, but the system will go "open loop" in about 15 seconds. For intermittent inspection, refer to INTERMITTENTS under the TESTS W/O CODES - EFI article.

Fig 1: Code 13: Circuit & Flow Chart, Open O2 Sensor Circuit

Courtesy of ISUZU MOTOR CO.