97 Concorde with P0140 oxygen sensor (downstream) code

Symptoms:

97 Chrysler Concorde has P0140 code (oxygen sensor circuit no activity detected). Engine runs good but check engine light showing up. Gas consumption a little bit higher.

Basic Concept:

The rear oxygen sensor located after the catalytic converter (CAT) monitors the CAT performance. The sensor should oscillate between between 0.6 and 0.9 volt. If stuck or no movement, the oxygen sensor maybe dead or contaminated or shorted.

Repair Strategies:

Replace the oxygen sensor first and monitor the voltage reading again. In case it is still erratic or not within range, check the CAT or sensor wirings. To improve gas mileage, do a quick top end tune up as shown in the picture. Make sure the cleaner is oxygen sensor compatible. ATS will supply the sensor wirings if required.