Powertrain Controls - ECM/PCM

Code 13 Chart:

Wiring Diagram For Oxygen Sensor Circuit:

CIRCUIT DESCRIPTION:

The ECM supplies a voltage of about 0.45 volt between terminals "D7" and "D6." (If measured with a 10 megohm digital voltmeter, this may read as low as 0.32 volts). The Oxygen sensor varies the voltage within a range of about 1.0 volt if the exhaust is rich, down through about 0.10 volt if exhaust is lean. The sensor is like an open circuit and does not produce a voltage when it is below 318°C (600°F). An open sensor circuit or cold sensor causes "Open Loop" operation.


TEST DESCRIPTION: The numbers below refer to circled numbers on the diagnostic chart.

1. Code 13 will set when:
a. Coolant temperature above 70°C (158°F).
b. At least 2 minutes engine run time after start.
c. Oxygen sensor signal voltage steady between 0.35 and 0.55 volts.
d. Engine speed above 1600.
e. Throttle position sensor signal is above 5%, approximately 0.3 volts above closed throttle voltage.
f. All conditions must be met for about 60 seconds. If the conditions for a Code 13 exist, the system will not go into "Closed Loop".
2. This will determine if the sensor is at fault or the wiring and ECM are the cause of a Code 13.
3. In doing this test, use only a high impedance digital volt ohm meter. This test checks the continuity of circuits 412 and 413. If circuit 413 is open, the ECM voltage on circuit 412 will be over 0.6 volts (600 mv).


DIAGNOSTIC AIDS:

Normal oxygen sensor "Scan" tool voltage varies between 100 mv to 999 mv (0.1 and 1.0 volts) while in "Closed Loop." Code 13 sets in one minute if voltage remains between 0.35 and 0.55 volts, but the system will go "Open Loop" in about 15 seconds. If Code 13 is intermittent, see DIAGNOSIS BY SYMPTOM.