Code 13 - Open O2 Circuit (A/F/J/N/P Body)
Code 13 will set: at least 2 minutes after engine start, with O2 signal voltage steady between .35 and .55 volt for more than one (1) minute, and with throttle position sensor signal above 6% (1200 RPM). The ECM supplies voltage of about .45 volt between terminals 8 and 15. (If measured with a 10 megohm digital voltmeter, this may read as low as .32 volt.) The O2 sensor varies the voltage within a range of about one (1) volt (rich exhaust) to .1 volt (lean exhaust). The O2 sensor is like an open circuit and produces no voltage when it is below about 600°F (360°C). An open sensor circuit or cold sensor causes open loop operation.
- Grounding diagnostic terminal with engine running activates "Field Service Mode". This allows the ECM to confirm either open or closed loop operation using the "SERVICE ENGINE SOON" light.
- This step verifies that no additional codes are stored, and that Code 13 is intermittent. See the CCC TESTS W/O CODES article in this section.
- This step simulates a lean exhaust. If ECM and wiring are okay, the ECM will see the lean condition and turn the "SERVICE ENGINE SOON" light off for at least 30 seconds after engine start, and then flash "open loop". It is considered normal if light remains off for a longer period of time before flashing open loop.