P0420 at ~165* intake temp. - Fuelly Forums

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Old 11-08-2008, 12:29 PM   #1
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P0420 at ~165* intake temp.

This has happened twice.

There is a lot of construction on the road that i live on. with my work schedule i get stuck in construction traffic in the morning and evening. The traffic crawls along just fast enough that i cant stop and turn the car off.

Water temps get up to around 220* if i dont turn the fan on. Chevy thought that 225* was a good temp to turn it on. Now with a manual fan switch like i have, it will throw a code if i go faster than 35 mph.

Getting to the point:

I have noticed that when intake temps reach about 165-170*, the check engine light comes on. The code it a P0420. According to www.obd-codes.com that could be caused by a number of things..

A code P0420 may mean that one or more of the following has happened:

* Leaded fuel was used where unleaded was called for
* An oxygen sensor is not reading (functioning) properly
* The engine coolant temperature sensor is not working properly
* Damaged or leaking exhaust manifold / catalytic converter / exhaust pipe
* Retarded spark timing
* The oxygen sensors in front and behind the converter are reporting too similar of readings
I am pretty sure its timing retard. Has anyone else with a 2.2 OHV Cavalier noticed this?

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Old 11-08-2008, 01:05 PM   #2
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Not that code but mine did give me a MAP sensor code p0105 last week. I believe the code means MAP malfunction. I reset it and it has not come back on. This was the 1st time the check engine light came on in the Cavalier since I purchased it last Jan. It had 79K on it then and has 90K on now.

2001 Chevy Cavalier 2d 5sp Best MPG 43.94

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Old 11-08-2008, 05:04 PM   #3
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# P0105 Manifold Absolute Pressure/Barometric Pressure Circuit Malfunction
you could try cleaning the sensor. if i am correct, the map sensor is mounted in the intake mani. if you take the intake off and dhine a light down the tb, you can see it gets nasty in there.

when i get the time i want to take mine off and steam clean it. i am also gonna replace the stock throttle body with one from a 2.4 cavalier z24 motor.
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Old 11-08-2008, 08:05 PM   #4
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been running a WAI for a few months now (max temp of 179 deg) and never had any code. doing a google search of that code showed a catalytic converter fault.

actually had a gas cap light that was legit (you know there had to be at least one legit one out there). I had cracks all in the seal in the gas cap, replaced the gas cap (really old) and the code went away. this is not related to what you have going on.

during the google search, it points to the converter itself and the oxy sensor (the one after the converter). if you reset this and take off the WAI, does the CEL go away? also remember that it takes a while for some tests to fully run before the CEL comes back on.
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