99suprduty

OK...06' GX470 CEL light and the others came on the other day when we got the cold snap. Gas cap is new so any chance for the quick fix is gone. Took it in and it threw that code...I've researched here and it could be the Cat of course or could be the O2 sensor.

Before I start throwing parts at this thing....is there a diagnostic check list for this code to follow?

Thanks!

Ali SC3

iTrader: (10)

I had this code come up when I started it in freezing weather. I borrowed a scanner and cleared it and it never came back. I think when its really cold out the ecu will pick up things aren't working that efficiently, which it is right, but its because its so cold out not that anything is actually wrong. I would reset it and see if it comes back, had it happen on a few other cars and most of the time it doesn't.

it could be related to o2 sensor if its old enough but then you would also get an o2 code eventually, but most often its just the cold weather that is the problem. the cats usually go for an extremely long time so its probably not that. hope it helps for me it was as simple as clearing the code with a scanner after the cold spell.

99suprduty

I think the guy tried to clear the code with the scanner but he wasn't inspiring my confidence. I'll unhook the battery and see if that works.

470SNC

I would try replacing the O2 sensor since its cheaper, then move on to the cat, you may need to replace both if the truck has a lot of miles

99suprduty

Ok....disconnected the battery and when I fired it up, the CEL and other lights didn't come back on. Don't know if that fixed it for good or not but I'll see if they come back or not.

BradTank

If the light comes back, a good code reader can tell pretty quickly if it's the cat or a bad O2 sensor by looking at the voltage readings.

Also, when cars get a lot of miles, often times the catalytic converter(s) just don't work as good as they should and it falls below the threshold of what's considered in compliance. So you could have a catalytic converter that's 89% efficient but the car's ECM says it's a "failed" catalytic converter.

The "right" way to fix this is with new catalytic converters, but I've also had GREAT success just throwing on an O2 sensor "spacer" on the one that's giving you an issue to get to code to go away. Or you can spend a few thousand at the Lexus dealership getting new catalytic converters

Ali SC3

iTrader: (10)

Those spacers do help on problem car's I had a corolla once that refused to be happy without it and everything was brand new replaced. sometimes the ecu is programmed too sensitive, there was even a model year of the celica/corolla 1zz or 2zz motors where they recalled customers in and flashed the ecu to not set off the light so much, basically made it less sensitive.

your last emission readings will tell you if you actually have a cat problem, post them up if you are not sure and we can take a look at it. if you passed by a wide margin then you shouldn't worry, as I said cat's generally don't go bad on these vehicles but the dealer won't tell you that. if you are only passing by a narrow margin I would check the o2 sensor's and do those if you have more than 60-80k on yours (only do the front ones not the post cat).

Like I said it happened to mine this winter, and I literally had my emission test done a few weeks back and it looks like a brand new car's results everything is only a small fraction of the limits, not even close to them.
HC: 0.028 out of 1.2 limit
CO: 0.5 out of 15 limit
NOX: 0.1 out of 2.0 limit

there is clearly nothing wrong with the cat or o2's here, the problem lies in the detection logic for that trouble code.
it just compares the pre o2's to the post o2's, and when its that cold the ecu adds a lot of cold fuel enrichment into the mix, and it makes it look like the cat isn't doing anything when it should be, partly I would guess because the cat is so cold it needs more time to warm up but I am not an expert as to how they programmed it I am just aware that it is not the best and this is a side effect of obd2.

majority of the time its just the cold weather throws the computers strict standards off, and the code will stay stored even though that problem lasted exactly 2 minutes after you started it literally that "one time" in cold weather. the code likely wont come back, mine hasn't . you think they would program these ecu detection logic better, but they don't, I don't think its designed to work perfectly all the time in freezing temps.

99suprduty

Don't have emissions testing out here!

Thanks for the info guys....truck was running fine with the CEL on so I think its something as you describe. I'll keep an eye on things...

Ali SC3

iTrader: (10)

no emissions, that must be really nice. yeah no reason to throw parts at this problem unless it keeps coming back in warm weather, then yes o2 sensors.