Is black soot on your catalytic converter an exhaust leak or a bad cat?

45

Asked by Guru5YP8J Sep 17, 2020 at 05:57 PM about the Cadillac DTS

Question type: Maintenance & Repair

I recently purchased a new catalytic converter for my Cadillac DTS( 6
months
ago),and just recently the  PO4020 code popped back upon my dash. I plan
on taking the vehicle back to the muffler shop,but today I looked under the
DTS, and saw that the catalytic converter heat shield had a small black soot
stain on it.This sounds like an exhaust leak to me,but my question is this,and
could the cat have already gone bad?

3 Answers

If you did not fix the problem that caused the cat to go bad the new one will not last long.

1 people found this helpful.
45

Thank you, and I appreciate the answers.I've owned many new Cadillacs,and I'm very familiar with North Star engines,and like any other vehicle,if your cat or 02 sensors go bad,and then you just replace them.I had my DTS inspected,and diagnosed by a reputable shop,and they found a bad catalytic converter. After I posted my question I dropped in at the repair shop,and in full disclosure I trust them,and why? Ive used there servces for years. Ron plugged in his scan tool, drove my DTS,and as Ron watched the live data feed,and what did Ron find? The catalytic converter,and 02 sensors are working perfectly, no misfire,ehaust leaks,injector issues,etc. Due to the fact that I've owned so many Cadillacs,and when my warranties ran out I took my Cadillacs to Ron,& why? He was a certified Cadillac mechanic for over twenty years. Ron is going to pull my plugs today,and why? To see if a spark plug maybe cracked or a bad wire,but again no misfire,and Ron also stated that my DTS may need a software update. Ron stated Tony according to our diagnostic machines which dealerships use,your DTS is in perfect working order,and why your throwing a Po4020 is a mystery.

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