Code 13, Open Oxygen Sensor Circuit (All Engines)
Code 13 will set with the engine operating temperature at least 2 minutes after engine start. The ECM must see: O2 signal voltage steady between .35 and .55 volts for more than 1 minute, or see TPS signal indicating not at idle. The ECM supplies a voltage of about .45 volt between terminals "D7" and "D8". (If measured with a 10 megohm digital voltmeter, this may read as low as .32 volts). The O2 sensor varies the voltage within a range of about 1 volt if the exhaust is rich, down to about .10 volt if the exhaust is lean.
- Grounding the diagnostic terminal with the engine running enables the "Field Service Mode", which allows the ECM to confirm either open or closed loop operation using the "CHECK ENGINE" light.
- This step verifies no additional codes stored and that Code 13 is intermittent. See CCC TESTS W/O CODES (TROUBLE SHOOTING) article.
- This step simulates a lean exhaust. If the ECM and wiring are OK, the ECM will see the lean condition and turn the "CHECK ENGINE" light off at least 30 seconds after engine start and then flash open loop. It is normal for the light to remain off for a longer period of time before flashing open loop.