DTC 13

Code 13 Chart:

Code 13 Wiring Diagram:

CIRCUIT DESCRIPTION:

The ECM supplies a voltage of about 0.45 volt between terminals "YD2" and "YD3". (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 oxygen sensor circuit or cold oxygen 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: Step numbers refer to step numbers on diagnostic chart.

1. Code 13 sets when:

^ No Code 21 or 22.

^ Engine at normal operating temperature.

^ Engine running for more than 4O seconds.

^ Signal voltage is steady between 0.35 and 0.55 volt.

^ Throttle position sensor signal above 0.55 volt.

^ All conditions must be met for about 30 seconds.

If the conditions for a Code 13 exists, the system will not go to "Closed Loop."

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

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

DIAGNOSTIC AIDS:

^ An intermittent may be caused by a poor connection, rubbed through wire insulation, or a wire broken inside the insulation.


Check for:

^ Poor Connection or Damaged Harness. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection, and damaged harness.

^ Intermittent Test, If connections and harness check OK, "Scan" 02 sensor voltage while moving related connectors and wiring harness, with warm engine running at part throttle in "Closed Loop." If the failure is induced "02 sensor voltage" reading will change from its normal fluctuating voltage (above 600 mV and below 300 mV) to a fixed value around 450 mV. This may help to isolate the location of the malfunction.