Fault code

[mikec041]

OK
I have a 2000 with a 2.2l recently i started getting a fault code translated to "Catalyst system efficiency below threshold". Can this be a failing O2 sensor or is it a defective Cat? Engine may bog down when code is set but not all the time, Most of the time only symptom is the MIL light.
Any ideas
Thanks.

[MT-2500]

Originally Posted by mikec041

OK
I have a 2000 with a 2.2l recently i started getting a fault code translated to "Catalyst system efficiency below threshold". Can this be a failing O2 sensor or is it a defective Cat? Engine may bog down when code is set but not all the time, Most of the time only symptom is the MIL light.
Any ideas
Thanks.

What is the mileage on tune up.
A lot of cat codes can be cause by engine running problem.
What was the code no?

http://www.troublecodes.net/articles/catfailure/

DTC P0420, P0421, P0430 & P0431: Check Possible Cause Of Misfire DTC P0420 and P0421 indicates bank one catalyst system efficiency is minimum requirement. DTC P0430 and P0430 indicates bank 2 catalyst system efficiency is minimum requirement. Possible causes are as follows: Use of leaded fuel. Oil contamination. Cylinder misfire. Fuel pressure too high. HO2S sensor improperly connected. Damaged exhaust system component. Faulty ECT sensor. Faulty HO2S. Ensure ignition timing is correct. Retrieve all Continuous Memory DTCs. If misfire code(s) is not present, go to next step. If misfire code(s) is present, isolate cylinder and repair as necessary. Check HO2S Monitor DTCs If DTCs P0136, P0138, P0140, P0141, P0156, P0158, P0160, or P0161 were present in step 1), service as necessary before continuing. If none of these codes are present in step 1), go to next step. Check ECT Sensor DTCs If DTCs P0117, P0118, P0125 or P1117 were present in step 1), service as necessary before continuing. If none of these codes are present in step 1), go to next step. If any codes except P0420, P0421, P0430 and/or P0430 were present in step 1), service as necessary before continuing. If no codes except P0420 and/or P0430 were present in step 1), go to next step. Check Rear HO2S Wiring Harness Turn ignition off. Ensure HO2S wiring harness is correctly routed and connectors are tight. Repair or replace as necessary. If wiring harness and connectors are okay, go to next step. Check Fuel Pressure Turn ignition off. Release fuel pressure. Install fuel pressure gauge. Start engine and allow to idle. Note fuel pressure gauge reading. Increase engine speed to 2500 RPM and maintain for one minute. For fuel pressure specifications, see FUEL PRESSURE SPECIFICATIONS article. If fuel pressure is as specified, go to next step. If fuel pressure is not as specified, go to CIRCUIT TEST HC . Check For Exhaust System Leaks If exhaust system leaks, it may cause catalyst monitor efficiency test to fail. Inspect exhaust system for cracks, loose connections or punctures. Repair or replace as necessary. If exhaust system is okay, go to next step. Check For Exhaust System Restrictions Inspect exhaust system for collapsed areas, dents or excessive bending. Repair or replace as necessary. If exhaust system is okay, go to next step. Ć Check Manifold Vacuum Install tachometer. Connect vacuum gauge to intake manifold vacuum source. Start engine and raise engine speed to 2000 RPM. Manifold vacuum should rise to more than 16 in. Hg. If manifold vacuum is okay, go to next step. If manifold vacuum is low, go to step 11). Leave tachometer and vacuum gauge connected. Start engine and raise engine speed to 2000 RPM. On a non- restricted system, manifold vacuum should quickly rise to normal range as increased RPM is maintained. On a restricted system, manifold vacuum will slowly rise to normal range as increased RPM is maintained. If manifold vacuum is okay, no indication of exhaust leak or restriction has been detected and testing is complete. If manifold vacuum is low or slow to respond, go to next step. Leave tachometer and vacuum gauge connected. Remove exhaust pipe from exhaust manifold. Start engineand raise engine speed to 2000 RPM. If manifold vacuum is now okay, fault is downstream from exhaust manifold. Reconnect exhaust pipe to exhaust manifold and go to next step. If manifold vacuum is still low or slow to respond, fault is in exhaust manifold or intake manifold gasket. Repair or replace as necessary and repeat QUICK TEST. Leave tachometer and vacuum gauge connected. Disconnect muffler/tailpipe assembly from rear of catalytic converter. Start engine and raise engine speed to 2000 RPM. If manifold vacuum is now okay, fault is in muffler/tailpipe assembly. Repair or replace as necessary and test drive vehicle to verify elimination of symptom. If manifold vacuum is still not okay, fault is in catalytic converter. Repair or replace as necessary. Check tailpipe/muffler assembly for debris from catalytic converter. Test drive vehicle to verify elimination of symptom.

[mikec041]

MT-2500
The code that's being thrown is a 420
Mileage since last tuneup (wires/plugs) was about 20k when it started, I recently replaced the plugs b/c of this. The whole thing started after filling up tank in Dover Delaware thought it was bad gas. Had lack of power/misfire and flashing MIL light but only when tank was over 1/2 full. Dumped the gas from tank replaced filter and since have had the MIL light with 420 that's why I'm thinking the O2s got burned by whatever was in the gas. Recently did throw a misfire code but that was a one time thing right after replacing plugs i think one of the wires lost contact, rechecked/secured wires and i don't hear/see any vacuum issues.
It's going to take me a few days to work through your advise, thanks I'll let you know how it works out.

[MT-2500]

Originally Posted by mikec041

MT-2500
The code that's being thrown is a 420
Mileage since last tuneup (wires/plugs) was about 20k when it started, I recently replaced the plugs b/c of this. The whole thing started after filling up tank in Dover Delaware thought it was bad gas. Had lack of power/misfire and flashing MIL light but only when tank was over 1/2 full. Dumped the gas from tank replaced filter and since have had the MIL light with 420 that's why I'm thinking the O2s got burned by whatever was in the gas. Recently did throw a misfire code but that was a one time thing right after replacing plugs i think one of the wires lost contact, rechecked/secured wires and i don't hear/see any vacuum issues.
It's going to take me a few days to work through your advise, thanks I'll let you know how it works out.

Good Luck
And as you see there is many things that can cause the code.
Could be 02 sensor but It needs proper testing to find the problem.
But always clear the code and see if it returns first step.
MT