DTC 13

DTC 13 - Oxygen Sensor Circuit (Open Circuit):

Oxygen Sensor Wiring Circuit:

Circuit Description:

The Engine Control Module (ECM) supplies a voltage of about .45 volt between terminals "YE14" and "YE15". (If measured with a 10 megohm digital voltmeter, this may read as low as .32 volt.) The oxygen sensor 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 360°C (600°F). An open oxygen sensor circuit or cold oxygen sensor causes "Open Loop" operation.

DTC 13 will set if:

^ Engine coolant temperature is above 50°C (122°F).
^ No DTCs 21 or 22.
^ Engine has been running at least 40 seconds.
^ 02S signal voltage is steady between 350mV and 550mV.
^ Throttle angle above 3.5%.
^ All above conditions must be met for about 30 seconds.

Test Description: Number(s) below refer to circled number(s) on the diagnostic chart.

1. If the conditions for DTC 13 exist, the system will not go to "Closed Loop."
2. This will determine if the sensor or the wiring is the cause of DTC 13.
3. In doing this test use only a high impedance digital multimeter (J 39200). This test checks the continuity of CKTs 412 and 413. If CKT 413 is open the ECM voltage on CKT 412 will be over .6 volt (600 mV).

Diagnostic Aids:

Normal scan voltage varies between 100mV to 999mV (.1 and 1.0 volt) while in "Closed Loop." DTC 13 sets in 30 seconds if voltage remains between 350 mV and 550 mV, but the system will go "Open Loop" in about 15 seconds.

- Intermittent Malfunctions