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3K views 9 replies 6 participants last post by  jadcock 
#1 ·
I have been having those following codes in my car DTC 420 and DTC 1189. A few days ago , those throwed by PCM then cleared them all . Today those same codes are back again and I just cleared the codes again . So , should I worry or shouldn't ?
Car seems pretty nice and with no visible symptoms such as backfire,missfire,dropping MPG ,hesitation.
 
#5 ·
Thanks guys ,for the oil pressure switch can I check it myself or have it checked by dealer ?
BTW car has 55K miles on it
 
#7 ·
Is it a factory Cat? How old is the cat? A brand new cat can set this code P0420 due to mat burn off, (Green Cat). Clear the code and see it returns.

An engine misfire can kill a good cat in a very short time. Also using fuel with high sulfur content will degrade the cat and set this code. You can try another brand of fuel, clear the code and drive it on the highway to clear any contamination.

P1189 is a circuit code, it should have nothing to do with P0420 which is a catalyst performance code.

Do you have less than 80K miles? If so take to the dealer the cat is still under warranty.
 
#9 · (Edited)
I checked the codes again this time DTC 420 was gone but DTC 442 replaced it .
DTC 1189 was on again and cleared them all
 
#10 ·
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