DTC 13

Code 13 Chart:

Oxygen Sensor Circuit:

CIRCUIT DESCRIPTION:
The ECM supplies a voltage of about 0.45 volt between terminals "C7" and "C8." (If measured with a 10 megohm digital voltmeter, this may read as low as 0.32 volts). When the Oxygen sensor 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 does not produce a voltage when it is below 316°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. Engine at normal operating temperature.
b. At least 40 seconds engine run time after start.
c. Oxygen sensor signal voltage steady between 0.35 and 0.55 volt.
d. Throttle angle is greater 5%.
e. All conditions must be met for about 2 minutes. 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." Verify a clean, tight ground connection for circuit 413. Open circuits 412 or 413 will result in a Code 13. If Code 13 is intermittent, Testing and Inspection