Diagnostic Aids

Normal scan voltage varies between .1-1.0 volt while in closed loop. Code 13 will set in one minute if voltage remains between .35-.55 volt. The system will go into open loop after about 15 seconds.

Verify a clean, tight ground connection for the O2 ground wire. Open in O2 ground wire and O2 signal wire will result in a Code 13. If Code 13 is intermittent, see INTERMITTENTS in TESTS W/O CODES article in this section.

Fig 1: Code 13 Schematic - Open Oxygen Sensor Circuit

Courtesy of GENERAL MOTORS CORP.

Fig 2: Code 13 Flow Chart - Open Oxygen Sensor Circuit

Courtesy of GENERAL MOTORS CORP.