Powertrain Controls - ECM/PCM

Code Chart 13:

Oxygen Sensor Wiring Circuit:

Circuit Description:
The Engine Control Module (ECM) supplies a voltage of about .45 volt between terminals "C7" and "C8". (If measured with a 10 megohm digital voltmeter, this may read as low as .32 volt.)

When the Oxygen Sensor (O2S) reaches operating temperature, it varies this voltage from about .1 volt (exhaust is lean) to about .9 volt (exhaust is rich).

The sensor is like an open circuit and produces no voltage when it is below 316°C (600°F). An open sensor circuit or cold sensor causes "Open Loop" operation.

DTC 13 Will Set When:
^ Engine is at normal operating temperature.
^ At least 40 seconds has elapsed since engine start up.
^ 025 signal voltage is steady between .35 and .55 volt.
^ Throttle angle is greater than 5%.
^ All above conditions are met for about 10 seconds.

Action Taken (ECM will default to): System will not operate in "Closed Loop." Malfunction Indicator Lamp (MIL) illuminates.

DTC 13 Will Clear When: Oxygen sensor voltage varies between 100 mV to 999 mV (.1 and 1.0 volt) while in "Closed Loop."

DTC Chart Test Description: Number(s) below refer to circled number(s) on the diagnostic chart.
1. During engine warm-up, the O2S heats up and its voltage begins to vary between 100 mV to 999 mV (.1 volt to 1.0 volt) while in "Closed Loop." This step determines if the O2S is operating property.
2. This test determines if the Oxygen Sensor (O2S) is the problem or if the ECM and wiring are at fault.
3. In doing this test, use only a 10 megohm digital voltmeter. This test checks the continuity of CKT 412 and CKT 413. If CKT 413 is open, the ECM voltage on CKT 412 will be over .6 volt (600 mV).

Diagnostic Aids:
Normal scan tool oxygen sensor voltage varies between 100 mV to 999 mV (.1 and 1.0 volt) while in "Closed Loop."

Verify a clean, tight ground connection for CKT 413. Open CKT 412 or CKT 413 will result in a DTC 13. If DTC 13 is intermittent, refer to "Diagnosis By Symptom." Testing and Inspection