1996 Chrysler Town and Country Failed Smog Test

TECNATIC

MEMBER
1996 CHRYSLER TOWN AND COUNTRY
6 CYL
FWD
AUTOMATIC
164,751 MILES

My 1996 Chrysler Town & Country 3.3L failed the smog test with more than double the allowable amounts for a gross polluter. The only OBDC code is P0140 which is "oxygen sensor ckt inactive (bank 1, sensor 2)". I replaced the oxygen sensor upstream of the catalytic converter but the code is still reading the same. Is that the code for the sensor downstream of the catalytic converter or the one upstream of it? The smog test technician seems to think that the problem is more likely due to a failed catalytic converter rather than just the oxygen sensor because of the extremely high readings of pollutants. What should I do?

1 Reply

BMRFIXIT

MECHANIC
19,053 POSTS

DOWNSTREAM O2 SENSOR STAYS AT CENTER.

Start and warm engine to normal operating temperature. Using scan tool, set engine speed at 1500 RPM. Using scan tool, read downstream oxygen sensor state.
If downstream oxygen sensor state does not change at least once every 10 seconds, go to step 7). If downstream oxygen sensor state changes at least once every 10 seconds, go to next step.
Wiggle wiring harness and connector at downstream oxygen sensor while monitoring downstream oxygen sensor state. Downstream oxygen sensor is mounted on exhaust pipe, behind catalytic converter.
If downstream oxygen sensor state becomes locked at the center while moving wiring harness, repair open circuit in wiring harness or connector as necessary. Perform TEST VER-5A. If downstream oxygen sensor state does not become locked at center while moving wiring harness, go to next step.
Conditions required to set DTC are not present at this time. If downstream oxygen sensor voltage is between.29 volt and.72 volt for 30 seconds, the Powertrain Control Module (PCM) pulls sensor voltage to 5 volts for 60 seconds and monitors the sensor voltage. If voltage stays at 5 volts, DTC will be stored in PCM. Possible causes are: sensor output wire open, open ground circuit, defective downstream oxygen sensor, defective connector terminals or wiring, dirt/moisture or grease inside connector, or defective PCM. Go to next step.
Check for defective wiring or connections at downstream oxygen sensor and PCM. The PCM is located between driver's side front fender and power distribution center, near battery. If defective wiring or connections exist, repair as necessary. Perform TEST VER-5A. If no defective wiring or connections exist, test is complete. Perform TEST VER-5A.
Turn ignition on with engine off. Disconnect connector at downstream oxygen sensor, mounted on exhaust pipe, behind catalytic converter. Using scan tool in ohmmeter mode, check resistance at terminal No. 3 (Black/Light Blue wire) on wiring harness side of connector for downstream oxygen sensor.
If resistance is more than 5 ohms, repair open circuit in Black/Light Blue wire between PCM and downstream oxygen sensor. Perform TEST VER-5A. If resistance is 5 ohms or less, go to next step.
Connect jumper wire between terminal No. 4 (Tan/White wire) on wiring harness side of connector for downstream oxygen sensor and positive battery terminal. Using scan tool, read downstream oxygen sensor voltage.
If downstream oxygen sensor voltage is more than one volt, replace downstream oxygen sensor. Perform TEST VER-5A. If downstream oxygen sensor voltage is one volt or less, go to next step.
Turn ignition off. Disconnect connectors from Powertrain Control Module (PCM). The PCM is located between driver's side front fender and power distribution center, near battery.
Disconnect jumper wire from wiring harness side of connector for downstream oxygen sensor and positive battery terminal. Using external ohmmeter, check resistance between terminal No. 4 (Tan/White wire) on wiring harness side of connector for downstream oxygen sensor and PCM connector terminal No. 51 (Tan/White wire).
If resistance is less than 5 ohms, replace PCM. Perform TEST VER-5A. If resistance is 5 ohms or more, repair open circuit in Tan/White wire between PCM and downstream oxygen sensor.