DTC 13

Diagnostic Chart





Circuit Diagram

Circuit Description
The Engine Control Module supplies a voltage of about 0.45 volts between terminals "B3" and "B2". (If measured with a 10 megohm digital voltmeter, this may read as low as 0.32 volts).
When the heated oxygen sensor reaches operating temperature, it varies this voltage from about 0.1 volts (exhaust is lean) to about 0.9 volts (exhaust is rich).
The heated oxygen sensor has a heater incorporated as part of the sensor. This heater is used to heat the sensor up, thus causing the heated oxygen sensor to produce voltage sooner. The heater portion of the sensor will not affect diagnostic trouble code 13 setting.
The sensor is like an open circuit and produces no voltage when it is below 300°C (572°F). An open sensor, or circuit sensor, could cause an "Open Loop" operation.

Test Description
The numbers below refer to the circled numbers on the diagnostic chart.
1. diagnostic trouble code 13 will set if;
- Engine operating temperature is above 69.5°C (157.1°F).
- At least 3 minutes have elapsed since engine start-up.
- Oxygen signal voltage is steady between 0.347 and 0.547 volts.
- Throttle angle is above 9.8%.
- No diagnostic trouble code 21 or 31 is set.
- All of the above conditions are met for about 40 seconds.

NOTE: If the conditions for a diagnostic trouble code 13 exist, the system will not go "Closed Loop".

2. This test determines if the heated oxygen sensor is the problem or if the Engine Control Module and wiring are at fault.
3. Use only a 10 megohm digital meter when performing this test. This test checks the continuity of "B3" and "B2". If "B2" is open, the Engine Control Module voltage on "B3" will be over 0.6 volts (600 mV).

Diagnostic Aids
- Normal "Scan Tool" heated oxygen sensor voltage varies between 100 mv to 999 mv (0.1 and 1.0 volts), while in "Closed Loop". diagnostic trouble code 13 sets in 40 seconds, if sensor signal voltage remains between 0.347 and 0.547 volts, the system will go "Open Loop" in about 15 seconds.
- Verify a clean, tight ground connection for "B2" at the engine mounting point. An open "B3" or "B2" will result in a diagnostic trouble code 13. If diagnostic trouble code 13 is intermittent, refer to DIAGNOSIS BY SYMPTOM.