DTC 13

Code 13 - Oxygen Sensor Circuit:

Wiring Diagram for Oxygen Sensor Circuit:

CODE 13 - OXYGEN SENSOR CIRCUIT

Circuit Description:


The Electronic Control Module (ECM) supplies a voltage of about .45 volt between terminals "D6" and "D7". (If measured with a 10 megohm digital voltmeter, this may read as low as .32 volt.) The 02 sensor varies the voltage within a range of about 1 volt if the exhaust is rich, down through about .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 sensor circuit or cold sensor causes "Open Loop" operation.


Test Description: Numbers below refer to circled numbers on the diagnostic chart.

1. Code 13 will set:

^ Engine at normal operating temperature

^ Up to 2 minutes engine time after start

^ 02 signal voltage steady between .35 and .55 volt

^ Throttle Position Sensor (TPS) signal above idle

^ 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 or the wiring is the cause of the Code 13.

3. In doing this test use only a high impedence digital volt ohmmeter. 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 .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 ECM harness connectors for backed out terminals "D7" or "D6", improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection and damaged harness.

^ Intermittent Test - If connections and harness checks out 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, the "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.