Overall Function Test

Start engine and warm to operating temperature. Turn ignition off. Using 3 DVOMs, connect leads by backprobing in the following manner: See Figure.

• DVOM No. 1 positive lead connected to PCM harness connector terminal No. 50.
• DVOM No. 1 negative lead connected to PCM harness connector terminal No. 25.
• DVOM No. 2 positive lead connected to PCM harness connector terminal No. 51.
• DVOM No. 2 negative lead connected to PCM harness connector terminal No. 25.
• DVOM No. 3 positive lead connected to PCM harness connector terminal No. 56.
• DVOM No. 3 negative lead connected to PCM harness connector terminal No. 25.

DVOMs No. 1 and 2 are measuring front (right and left) HO2S voltage And DVOM No. 3 is measuring rear HO2S voltage. Start engine and increase to 2000 RPM and hold steady. Monitor DVOMs and ensure DVOM No. 3 voltage switching frequency (between high and low voltage) is at least 50 percent slower than DVOMs No. 1 and No. 2. If operation is not as specified, three way catalyst is not operating properly. If voltage of DVOMs No. 1 or 2 does not switch (between high and low voltage) at least 5 times within 10 seconds, diagnose fault in appropriate front HO2S circuit. See DTC P0130 OR P0150: FRONT (RIGHT & LEFT) HEATED OXYGEN SENSOR (HO2S) .