Needing help here. Have a 2000 XJ and today while driving the check engine light went on. Took it to autozone where they ran the code P0420. The Catalytic converter and a few other possibilities. Do i need to replace it? I disconnected the battery and cleared the code so i dont have to look at it. Hope it stays off for a while till i get this figured out. It runs fine ... For 207,000 miles.

 

Here's P0420:

P0420-1/1 CATALYTIC CONVERTER EFFICIENCY

When Monitored: After engine warm up to 147 deg. F, 180 seconds ofopen throttle operation, at a speed greater than 20 mph, with the engine at1200-1700 rpm and MAP vacuum between 15.0 and 21.0 inches of mercury (Hg).

Set Condition: As catalyst efficiency deteriorates, the switchrate of the downstream O2 sensor approaches that of the upstream O2 sensor. Ifat any point during the test the switch ratio reaches a predetermined value acounter is incremented by one.

POSSIBLE CAUSES

EXHAUST LEAK

CATALYST EFFICIENCY DTC DOES NOT RECUR

ENGINE MECHANICAL PROBLEM

CATALYTIC CONVERTER 1/1

UPSTREAM O2 SENSOR OLDER THAN DOWNSTREAM O2 SENSOR


Is this your exhaust system? Could be a downstream O2S at fault. If you elect to change your O2S's, I recommend you change them all (NTK Sensors as listed).

 

I did start the car up after this morning and noticed a little bit of condensation leak out of the area of the cat. converter . maybe a leak