2004 Jeep Grand Cherokee P0420 and P0325

Tiny
GREENCHEVYMALIBU
  • MEMBER
  • 2004 JEEP GRAND CHEROKEE
  • 4.7L
  • V8
  • 2WD
  • AUTOMATIC
  • 140,000 MILES
STFT B1 -10.9%
LTFT B1 7.8%
STFT B2 -4.7%
LTFT B2 6.3%

Engine rpm 1472
Vehicle speed 40
ECT 210.2
MAP(inHg) 10.9

Knock sensor code doesn't always trigger.

I have a live data scanner. What should I look for?
Friday, April 17th, 2015 AT 7:12 AM

4 Replies

Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
See pic for causes but with the converter being bad 420 code that may set it off as well. Converter probably needs to be replaced.
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Friday, April 17th, 2015 AT 7:34 AM
Tiny
GREENCHEVYMALIBU
  • MEMBER
  • 230 POSTS
Would it better to replace both pre cats? Then just one?
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Friday, April 17th, 2015 AT 8:33 AM
Tiny
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  • MEMBER
  • 230 POSTS
Could the bad cat be causing the knock sensor code?
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Friday, April 17th, 2015 AT 10:40 AM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Teh cat system may be in one piece so both get replaced at same time. And that is what I ameant when I said the 420 code may set the other code.
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Friday, April 17th, 2015 AT 12:06 PM

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