DTC 13

Code 13 Chart:

Code 13 Wiring Diagram:

CIRCUIT DESCRIPTION:

The Electronic Control Module (ECM) supplies a voltage of about 0.45 volt between terminals "YE14" and "YE15". (If measured with a 10 megohm digital voltmeter, this may read as low as 0.32 volt.) The O2 sensor varies the voltage within a range of about 1 volt if the exhaust is rich, down through about 0.10 volt if exhaust is lean. 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.

NOTE: Because of all the possible color code combinations used on electrical wiring diagrams, always refer to ECM CONNECTOR IDENTIFICATION under ELECTRICAL AND ELECTRONIC WIRING DIAGRAMS for correct color code identification of circuit.

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

1. Code 13 will set:

^ Engine at normal operating temperature
^ At least 2 minutes engine time after start.
^ 02 signal voltage steady between 0.35 and 0.55 volt.
^ Throttle position sensor signal above 4%.
^ All conditions must be met for about 60 seconds. If the conditions for a code 13 exist the system will not go "Closed Loop".

2. This will determine if the sensor is at fault or the wiring or ECM is the cause of the Code 13.

3. In doing this test use only a high impedence digital volt ohm meter. This test checks the continuity of CKTs 412 and 413 because if CKT 413 is open the ECM voltage on CKT 412 will be over 0.6 volt (600 mV).

DIAGNOSTIC AIDS:

Normal "Scan" voltage varies between 100 mV to 999 mV (0.1 and 1.0 volt) while in "Closed Loop". Code 13 sets in one minute if voltage remains between 0.35 and 0.55 volt, but the system will go "Open Loop" in about 15 seconds. Refer to TESTING PROCEDURES/DIAGNOSIS BY SYMPTOM/INTERMITTENTS..