Parts 6E2-76 SOHC & DOHC Code 45 O2 Sensor Rich Ex.

Fig. 6E3-14:

6E3-28 DRIVEABILITY AND EMISSIONS (DOHC TURBO)

CODE 13

OXYGEN SENSOR CIRCUIT (OPEN/GROUNDED CIRCUIT)


Circuit Description:

The 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). When the O2 sensor reaches operating temperature, it varies this voltage from about .1 volt (exhaust is lean) to about .9 volt (exhaust is rich). The O2 Sensor has a heater incorporated as part of the sensor. This heater is used to heat the sensor up, thus causing the O2 sensor to produce voltage sooner. The heater portion of the sensor will not affect how Code 13 sets. The sensor is like an open circuit and produces no voltage, when it is below 360~C (600~F). An open sensor circuit, or could sensor, causes "Open Loop" operation.

Test Description:

Numbers below refer to circled numbers on the diagnostic chart.
(1) Code 13 will set under if:
^ Engine operating temperature above 70~C (158~F).
^ At least 2 minutes have elapsed since engine start-up.
^ O2 signal voltage is steady between 0.42 volt and 0.55 volt.
^ Throttle angle above 10%.
^ All above conditions are met for about 4 seconds.

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

(2) This test determines if the O2 sensor is the problem or if the ECM and wiring are at fault.
(3) Use only a 10 megohm digital when performing this test. This test checks the continuity of "D7" and
"D6". If "D6" is open, the ECM voltage on "D7" will be over .6 volt (600 mv).

Diagnostic Aids:

Normal "Scan" tool O2 Sensor voltage varies between 100 mv to 999 mv (.1 and 1.0 volt), while in "Closed Loop". Code 13 sets in one minute, if sensor signal voltage remains between .347 and .547 volt, but the system will go "Open Loop" in about 15 seconds. Verify a clean, tight ground connection for "D6" at the engine mounting point. Open "D7" or "D6" will result in a Code 13. If Code 13 is intermittent, refer to "Symptoms", Section "6E3-B".