2003 Chevy Tahoe Chevy Tahoe 2003 drive cycle.

APPST8DESIGN

MEMBER
2003 CHEVROLET TAHOE
V8
2WD
AUTOMATIC
125,625 MILES

So here is the story.

I originally had code P0420 catalyst efficiency code which only set off the check engine light during the winter months then all summer it would be fine. I read that it could possibly be the coolant temperature sensor which could cause the computer to read the CC emissions when the engine wasn't warm. I replaced both bank 1 O2 sensors and the coolant temperature sensor then reset the codes. Then I started getting P0171 bank 1 is running too lean code. I checked for vacuum leaks (there weren't any) and cleaned the MAF sensor which then turned the light off. Now I'm trying to get it to pass inspection and after driving it for 200 miles (after reseting codes) the drive cycle still hasn't tripped the catalyst sensor or evaporative system. Any idea on what the cycle for those sensors is for my year, make, and model? Could this be a result of a lose connection?

4 Replies

BRIAN 1

MECHANIC
1,030 POSTS

On the cat and evap system sometimes the drive cycle is 300 miles or more because it takes longer for these vehicles to run an evap and cat test.plus if you have a p0420(which means you usually replace the cat)when it runs the test on the cat if there is a problem inside it will reset p0420.also a malfunctioning cat will cause a p0171.check this ground firstmake sure its clean and tight,if it is you might be replacing the cat converter.

post back with what you find.

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Monday, January 11th, 2010 AT 3:17 PM

APPST8DESIGN

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14 POSTS

The P0420 code has disappeared, it tends to come and go with the temperature outside. Cold weather = P0420 code, Warm weather = no codes. That's why I switched out the Coolant Temp Sensor. I was thinking for 12 bucks why not try it?

Let me ask you this. If it is the CC and I buy a new OEM CC from the dealer is it possible to put it in without welding? Is it as easy as dropping the muffler putting a new one in and reattaching it? (Also this may be a dumb question but I'll ask it anyway) If I do pull that CC off is it possible to clean it out with a cleaner of some sort to increase its efficiency?

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Monday, January 11th, 2010 AT 3:42 PM

BRIAN 1

MECHANIC
1,030 POSTS

Question 1:yes question 2:no, as far as replacing it, not very hard, its a crossover pipe that goes into 2 seperate cat converters and into the muffler. You will have to remove the trans crossmember to get the pipe out, no welding at all. As far as cleaning it you really cant, once the ceramic monolith substrate breaks down its no good, which is the inside of the cat, it cannot be cleaned. Once its replaced it will be efficent and the gas milage would improve. Only problem is the OEM cat is VERY expensive.

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Monday, January 11th, 2010 AT 5:15 PM

APPST8DESIGN

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14 POSTS

Cleaned and tightened the wire you suggested (only one end couldn't reach the other end without removing a bunch of stuff). It was already pretty tight though and relatively clean.

The evap system and catalytic system are still reading "not ready" so I'm not sure if anything is fixed yet. Went to the dealership and he said it should have read after 50 or so miles.

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Thursday, January 14th, 2010 AT 9:56 AM