Code 13 - Open Oxygen Sensor Circuit
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% (.8 to 1.2 volt). The ECM supplies voltage of about .45 volt between terminals "D7" and "D6". (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 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.
NOTE:
The following step numbers refer to the numbers in the accompanying flow chart(s).
- Grounding the diagnostic terminal with the engine running activates the "Field Service Mode." This allows the ECM to confirm either open or closed loop operation using the "SERVICE ENGINE SOON" light.
- This step verifies no additional codes are stored, and that Code 13 is intermittent.
- This step simulates a lean exhaust. If the ECM and wiring are good, 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 the light remains off for a longer period of time before flashing open loop.