eric_in_sd

I launched another thread regarding my P0420 ("cat converter") code on my 2007 GL450, 111K miles.

In digging into it, I got to wondering whether replacing the oxygen sensors might be a good idea, regardless of whether I end up having to replace the cat. Apparently in some cases they become marginal before they trigger a OBDII code.

I couldn't find much information on the typical lifetime of the sensors.

There are also a bunch of different sensors available.

So, your recommendations? Replace the sensors, or wait? If I replace the sensors, stick with Bosch / OEM? Or Denso or whatever?

ALKEMIST187

Have you installed the o2 sensors? I have it done it on my escalade, was pretty easy, was it easy for you to install on your gl450? thanks

BlownV8

200k on my GL with original sensors.

ALKEMIST187

So the cat can go bad without the o2 going bad? Any precautionary things I can do before i try to find some used cats?

eric_in_sd

From what I hear, the cat can certainly go bad on its own. But changing the cat is at least 10x the service of changing the sensors, so it seems like changing the sensors is worth a try. I posted a couple of notes on the other thread regarding this.

BlownV8

If you need to replace the cats, I would go with an aftermarket high flow cat. No need to spend the big bucks on the MB system. I've had cats go bad on another MB before it hit 100k miles so it's not out of the realm. The O2 sensors on that car were fine.

When is the last time you changed your plugs? I'm still running the original plugs but plan to change them soon. Not having any symptoms but am pushing it with the high miles. The OE plugs are very durable.

eric_in_sd

California, baby, California. Options are basically zero. No aftermarket, no recertified, no nothing.

All because Los Angeles has smog.

BlownV8

Not according to the CARB website. http://www.arb.ca.gov/msprog/aftermk...ktcatdbase.htm

eric_in_sd

Well, I'll be. I stand corrected.

I tried to get a recertified catalytic converter shipped from Minnesota. They were like, no way, no how, no dice. Maybe it's just the used ones that California won't allow.

Note there is no application for GL450 on their exempted list.

BlownV8

I believe you just need one that is CARB certified for use in a vehicle in the GL's class.

eric_in_sd

I looked around and couldn't find any aftermarket units. I have no idea why this is.

BlownV8

Check ebay or do a Yahoo/Google search. My SL came from California with aftermarket high flow metal cell cats so there are shops that will do the conversion.

eric_in_sd

Now I'm really getting curious. One of the reasons the GL cat freaks me out is it's welded in to a big long exhaust pipe. Short of pulling the engine (I think) you'd have to cut the pipe.

I notice there are no direct applications for SL in the CARB database. I wonder if that's because they didn't bother to do the application for a high dollar low volume car.

Was your SL registered in California after the cat replacement?

I'll bet most smog guys barely look under the car, let alone verify it's a certified cat for that vehicle.

I poked around on ebay - that's how I found the recertified cat in Minnesota - but found very little. If I get more 420 errors, I'll look into it some more.

BlownV8

Yes, it was registered and smogged after they were installed. I would do the search for OBDII CARB certified universal catalytic converter.

noud

Whats up, mate?

we are in the same boat with p0420 and cali smog thigs.

Did you figure out anything with it?

eric_in_sd

Nothing. It hasn't come back after I put the Guaranteed To Pass through the tank. I also passed smog recently, so I got a couple more years.

You still getting 420 errors?

Maybe the truck is telling you it wants to get high.

noud

lol=) Yep, code comes and goes and makes me scream


everytime i see it=)

nishboo

Was changing the O2 Sensor (pre-cat) difficult? Can it be done with jack stands / ramps?

eric_in_sd

I still haven't done it. Really ought to, so as to eliminate that as a variable. I'm now getting 174 & 175 messages, likely culprit the mass airflow sensor. However, when you have a system, comprised of multiple items with limited lifespans, it's generally wise to change them out.

I suspect you can remove the sensors after removing the heat shields, so I'll try that.

Heating the mounting nut with a propane torch is easy enough. The talk of PB Blaster, Liquid Wrench, etc., is silly.

eric_in_sd

Sounds like you're working with a pre-OBDII vehicle. Is it younger than 1996?

nishboo

Planning to remove mine later today and replace.

Codes were for P0304 and P2196.
Cleared them off, codes came back. Changed out the coil for Cylinder 4.
Code P2196 came back a few times.
Cleared it off, and now P0303 and P0304. Running really rough.
Tested fuel injectors via SDS, and they seem correct.

Is it possible the O2 sensor could be the reason why the right bank is misfiring?

eric_in_sd

The OBD codes are a mixed bag, both informative and not. For example, the misfire is diagnosed only by crankshaft position - the misfire is a sudden slowing of the motor.
Sounds like 2196 is a sensor fault, and the computer is good enough at diagnosing that. It's clearly telling you the sensor is fried. You may have a bad electrical connection, but if you haven't messed with those connections, well, the sensors do fail.
The rough running is due to the system switching to open loop, that is, not using the oxy sensor at all but rather just a lean mix based on the mass air flow sensor, coupled with (I think) shutting off fuel to the cylinder it suspected was at fault. So the rough running is alarming but is not a direct indication of what is wrong. You can look at the oxy sensor lambda (which is the air-fuel ratio, with 1.00 being optimal) with your tool as the motor is idling. When running rough, you should see that bank sitting at some number higher than 1, given that 1/4 of the injectors on that bank are no longer shooting fuel. Since you had 03 and 04, it's probably shut off fuel to both, and the lambda should be like 1.4 or so.

Keep the coil you pulled off; it may still be good.

Let me know if you can get the sensor out with taking the heat shields off.

BlownV8

No, my SL600 is a 2005.

nishboo

Unplugged 02 sensor. Seems to get rid of check engine light immediately.

Put in new 02 sensor from under the car. Put it on ramps and stands. Wasn't too bad.

It runs fine now, but still trying to chase the issue I previously had started with. After the car is at a stoplight, if I let go of the brake it bucks back and forth. Any ideas?

eric_in_sd

Great news about the sensor! I guess it's the bank 2 sensor that's the worst. At 150k miles I really ought to do them all. Did you use a torch, Liquid Wrench, or just sheer brawn?

The clearing CEL from unplugging the sensor doesn't mean anything; it's just that the "sensor is bad" error went away, soon to be replaced by "sensor is missing".

Do you have any pending or stored codes? I discovered that the computer took time to self clear the P0305, so after a bunch of work it turned out to run fine after i changed the #5 coil AND cleared the code. Possibly the system is sniffing around to see if the 304 error is still a problem.

Since you have a new sensor in place, I'd clear all the codes and monitor the system from start. You mentioned SRS; do you have that with you? If not, get one of the "pocket" systems like the MBII or iCarsoft.

If you're up for the work, put the old #4 coil back in and see if the 304 error comes back. Kinda hard to justify when the coils are to be had for under $20, but I'm such a glutton for punishment I'd do it.

"Wut!" I hear you saying, "Those coils are $50 apiece!" First, get the Delphi coils. The Bosch are literally just the Delphi with a sticker on top. Second, you can find both the Bosch and Delphi as open box items on Ebay and Amazon Warehouse. The other brands are marginal and I wouldn't take a risk on them.