DTC 13

Code 13 Diagnostic Chart:

Oxygen Sensor Circuit Diagram (Heated Sensor):

CIRCUIT DESCRIPTION:
The PCM supplies a voltage of about 0.45 volt between terminals "BD2" and "BD3". (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 360°C (600°F). An open oxygen sensor circuit or cold oxygen sensor causes "Open Loop" operation.

Code 13 sets when:
^ 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 indicates throttle opening greater than 3%.
^ All conditions must be met for about 30 seconds.

TEST DESCRIPTION
Numbers below refer to step numbers on diagnostic chart.
1. Checks to see if computer will go into closed loop. If code 13 is valid and the condition is a hard failure (fault still exists), system should not switch from open to closed loop operation.
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 PCM voltage on CKT 412 will be over 0.6 volt (600 mV).

DIAGNOSTIC AIDS:
^ An intermittent may be caused by a poor connection, worn 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.