Powertrain Controls - ECM/PCM

Oxygen Sensor Circuit Code 13:

Oxygen Sensor Circuit:

Circuit Description:
The 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 Oxygen (02) sensor varies the voltage within a range of about I 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 about 315°C (600°F). An open sensor circuit or cold sensor causes "Open Loop" operation.

Test Description:
Number(s) below refer to circled number(s) on the diagnostic chart.

1. Code 13 will set if:
^ Engine temperature greater than 70°C (158°F)
^ At least 2 minutes engine time after start
^ Oxygen sensor 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 is at fault or the wiring or ECM is the cause of Code 13.

3. In doing this test, use only a high impedance digital volt ohmmeter. This test cheeks 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 Tech 1 "Scan" tool 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. Verify a clean tight ground connection for CKT 413. Open CKT 412 or CKT 413 will result in a Code 13.