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 "D7" and "D6". (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 315~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

^ At least 2 minutes engine time after start

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

^ RPM above 1600

^ Throttle Position Sensor (TPS) signal above 12% (about .5 volt above closed throttle voltage).

^ All conditions must be met for about 20 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 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:


Normal "Scan" voltage varies between 100 mV to 999 mV (.1 and 1.0 volt) while in "Closed Loop." Code 13 sets in one minute if voltage remains between .35 and .55 volt, but the system will go "Open Loop" in about 15 seconds.

Refer to "Intermittents" in Diagnosis By Symptoms - No Trouble Codes Stored.