DTC 63

DTC 63 Chart Oxygen Sensor Circuit:

Oxygen Sensor Circuit Wiring Diagram:

Circuit Description:

The ECM supplies a voltage of about 450 mV between terminals "D6" and "D16". (If measured with a 10 megohm digital voltmeter, this may read as low as 320 mV.) The oxygen sensor varies the voltage within a range of about 1000 mV if a rich O2 Sensor signal is indicated, down through about 10 mV if a lean O2 Sensor signal is indicated.

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

1. DTC 63 will set:

^ Engine at normal operating temperature (above 70°C/158°F).
^ At least 2 minutes engine running time after start.
^ O2 Sensor signal voltage steady between 350 mV to 550mV.
^ Throttle position sensor signal above 5% (about 0.3 volt above closed throttle voltage).
^ All conditions must be met for about 60 seconds. If the conditions for a DTC 63 exist, the system will not go into "Closed Loop."

2. This will determine if the oxygen sensor is at fault or the wiring or ECM is the cause of the DTC 63.

3. For this test use only a high impedance digital volt ohmmeter. This test checks the continuity of CKT 1666 and CKT 351. If CKT 351 is open, the ECM voltage on CKT 1666 will be over 0.6 volt (600 mV).


Diagnostic Aids:

Normal voltage readings vary between 10 mV to 1000 mV (.01 and 1.0 volt), while in "Closed Loop." The system will go into "Open Loop" operation when DTC 63 sets. - Intermittent Malfunctions