DTC 13

Fig. 008 - WIRING DIAGRAM for Code 13 Open Oxygen Sensor Circuit. VIN J:

CODE 13, OXYGEN SENSOR CIRCUIT

Code 13 will set:
a. Engine at normal operating temperature
b. At least 2 minutes engine time after start.
c. O2 signal voltage at terminal D7 of ECM steady between .35 and .55 volts for more than one minute.
d. Throttle position sensor signal above 6% (.8 to 1.2 volt).

Possible causes of a Code 13 are:
- A faulty O2 Sensor
- Faulty wiring or terminals
- A faulty ECM
The ECM supplies a voltage of about .45 volt between terminals "07" and "08". (If measured with a 10 megohm digital voltmeter, this may read as low as .32 volts.) The O2sensor varies the voltage within a range of about 1 volt if the exhaust is rich, down through about .10 volt if exhaust is lean.
The sensor is like an open circuit and produces no voltage when it is below about 360°C (600°F). An open sensor circuit or cold sensor causes open loop operation.

Fig. 007 Chart - Code 13 Open Oxygen Sensor Circuit:

1. 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 "SERVICE ENGINE SOON" light.
2. This step verifies no additional codes stored, and that stored Code 13 is intermittent.
3. This step simulates a lean exhaust. If the ECM and wiring are OK 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 should be considered normal if the light remains off for a longer peried of time before flashing open loop.