Hey guys new member! I own a limo company - First Class Limos. This is on our 2004 escalade limo. The car is not overheating and running at normal operating temp but we were getting warm A/C lately and we just drained the system and recharged it a few weeks ago. We have a check engine code showing code p0420, a google search shows this for that code:

The catalytic converter has an oxygen sensor in front and behind it. When the vehicle is warm and running in closed loop mode, the upstream oxygen sensor waveform reading should fluctuate. The downstream O2 sensor reading should be fairly steady. Typically the P0420 code triggers the Check Engine Light if the readings of the two sensors are similar. This is indicative of (among other things) a converter that is not working as efficiently as it should be (according to specs).


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


The engine is running normal operating temps but the fenders of the car get extremly hot hot hot!!! I just noticed this today and I don't think thats normal for the escalade as our hummer h2 fenders aren't hot at all. Anybody else have experience with this? Would this affect our Air conditioning? The air flow coming out of the exhaust feels fine and just as much as our h2's. Do you think it could be the o2 sensor or a clogged cat? Any suggestions would be helpful! Thanks!!!

Heres the car:
http://www.firstclasslimos.net/white-escalade-limo14.jpg
http://www.firstclasslimos.net/escalade-dance-floor.jpg (http://www.firstclasslimos.net/white-escalade-limo.html)

Humm.. Check the radiator fan. is it turning on? It should turn on when you turn on the AC.

Seems like the radiator fan is not working due to:

Bad temp sensor
Bad relay
Bad Fan
Blown Fuse
or a cobination of the above.

If the fan does not come on, the AC compresssor will not turn on at higher temps to preserve the system.

Well the engine fan runs, we have seen it run everytime we pop the hood, and if the engine fan wasn't running the car would surely overheat. The fan is not an electric fan.

We do have an extra fan that we mounted on all of our hummer limos and the escalade limo. Here is a pic of the setup on our hummer h2 limo which is the same on our escalade but much easier to get a pic of since the h2 hood doesnt fully open like the hummer.

http://www.firstclasslimos.net/h2fan.jpg

So theres the engine fan and then this extra fan which runs all the time as soon as the car powers up to help with extra cooling and air conditioning especially when idiling at weddings etc.

Are you sure the fans are working together and not against eachother? The stock fan pulls air in, your other fan should PUSH air in. If it pulling air as well, then once cancels the other.

Either way, you have a cooling problem FOR SURE. check the rad, fans ect.. The hood and fenders should be warm but not hot.

I'm almost positive that the fan is pushing air into the radiator towards the fan which would be the correct way. I will double check on monday.

It turns out our A/C problem was a bad compressor even though we put a new one in a month or two ago I think the parts store gave us the wrong one, so we got a replacement for free and the A/C seems to be solved.

As of the p0420 code we replaced the 02 sensor and the check engine light came back on. The car has been running every week doing limo runs with no problems. What could still cause the code to be on? A bad cat? How can you really check if one is bad without cutting it off?

I'm almost positive that the fan is pushing air into the radiator towards the fan which would be the correct way. I will double check on monday.

It turns out our A/C problem was a bad compressor even though we put a new one in a month or two ago I think the parts store gave us the wrong one, so we got a replacement for free and the A/C seems to be solved.

As of the p0420 code we replaced the 02 sensor and the check engine light came back on. The car has been running every week doing limo runs with no problems. What could still cause the code to be on? A bad cat? How can you really check if one is bad without cutting it off?

You can check exaust pressure. A pressure gauge on the O2 fitting beffore and after the cat. Check for a big pressure difference.

Fiero, Thanks alot for your help so far!

Any updates yet?

Take care,
Eric

Well the ac is back to normal with the new compressor. However here in Ohio is cold now so we're not even using AC anymore. We did take out the one extra fan in front instead of being one right in the middle we have two now in front one on each side. I havn't been able to check if the fenders are still hot to the touch because I have to catch it after its been running for a long time. The car never overheats or anything. After we replaced the sensor and reset the code it came back after a few days. I'll keep ya updated when I get more info.

thanks for your help!

-Jimmy

Ok I got to feel the fenders and the passenger side fender was cold and the driver side was warm probably due to the 2nd alternator on that side. We had to rerun the 2nd alterntor to run all the time to kick start the 2nd battery for the power in back because we were having power problems since we switched it and had to switch it back. So now the 2nd alternator has to run all the time instead of just when the power in the back is on until we find a different way. It should be ok for winter now but in the summer all that extra heat from the 200amp alternator might hurt AC and operation. We do drive 2 hours away for some runs and 2 hours back regularly.