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Dodge Repair/'01 Dakota 3.9L: P 0420, 0432


QUESTION: Sir, I keep getting error codes P0420 and P0432. I have found some vacuum leaks and repaired, replaced the oxygen sensor, replaced the TPS sensor, Pulled the throttle body and cleaned it. I also ran Cataclean through it to clear the catalytic converters. The check engine light comes on Just when I think I have it fixed. What other steps or where to look to fix this? Thank you.

ANSWER: Hi David,
Let me finish breakfast and get back to you with my answer.

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QUESTION: waiting for your response.

ANSWER: I just sent you a revised answer to your initial question.

---------- FOLLOW-UP ----------

QUESTION: The engine runs very well, It has about 168,000 on it. I did change the pre cat sensor on the passenger side. I'm trying to figure out if The errors are coming from passenger side or the drivers side or both.. I forgot to mention that after it warms up sometime it runs rough at an idle at one stoplight go to another and it runs smooth again. Should i replace the second sensor  on that side? I have ran the truck yesterday and  today, about 20 miles each with no check engine light coming on.

Hi David,
One code is for the left converter pathway and one is for the right pathway, so both sides are detecting the problem. My thought is that the rough idle may be causing the issue. In the absence of any other codes my suggestion would be to check whether the exhaust gas recirculation valve may be sticking ajar when you slow down to a stop.
I am not certain whether the Dakota has an egr, so if not then my suggestion would be to consider replacing the other three oxygen sensors. These codes are based upon comparing the behavior of the before and after sensors, and it is possible that either or both could be bad, and of course you have them on both sides of the exhaust system. But first look for the egr:
Look for the valve by following a narrow diameter exhaust pipe that branches off the rear side exhaust manifold. The valve has a round vacuum-operated top piece and between that and the body of the valve there is a flange which may hide from view the valve stem. So find that stem and notice that it has a slot into which you can insert the tip of a screwdriver. Move the stem back and forth and notice if it is closing tightly to a dead stop via the internal spring-action. If it is sticky then spray some solvent like WD-40 on the stem where is enters the body of the valve, and then work the stem a bit more to free up the action. That may solve both problems.
Thank you for the rating and nomination.

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Roland Finston


Get a Free Fast answer to your repair question about a Chrysler/Dodge/Plymouth car, minivan, SUV, or truck. Problems with electronically controlled engines and transmissions as well as body wiring problems are my specialty. This free troubleshoot advice forum helps you diagnose faults, minimize repair costs or do-it-yourself.

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