Overall Function Test

Start engine and warm to operating temperature. Turn ignition off. Using 2 DVOMs, connect leads by backprobing the connector in the following manner: See Figure.

• DVOM No. 1 positive lead connected to PCM connector terminal No. 50.
• DVOM No. 1 negative lead connected to PCM connector terminal No. 43.
• DVOM No. 2 positive lead connected to PCM connector terminal No. 56.
• DVOM No. 2 negative lead connected to PCM connector terminal No. 116.

DVOM No. 1 is measuring front HO2S voltage and DVOM No. 2 is measuring rear HO2S voltage. Start engine and increase to 2000 RPM and hold steady. Monitor DVOMs and ensure DVOM No. 2 voltage switching frequency (between high and low voltage) is at least 25 percent slower than DVOM No. 1. If operation is not as specified, three-way catalyst is not operating properly. If voltage of DVOM No. 1 does not switch (between high and low voltage) at least 5 times within 10 seconds, diagnose fault in front HO2S circuit. See DTC P0130, P0133 OR P0134:  FRONT HEATED OXYGEN SENSOR (HO2S).