mre2000

I think I've successfully worked through my CEL issues on my 98 ES300, and want to take it down to get it smogged.

I've driven off a few hundred miles and a tank and a half of gas since clearing out the last DTC's

The CEL has remained off, and all monitors have completed EXCEPT the CAT monitor (this is PROGRESS as I've been unable to get the O2 and O2 heater to complete).

I now have a PENDING CODE P0420 "catalyst system efficiency below threshold bank 1"

I've continued to drive the car, but the code neither clears, nor sets the CEL. Have repeated the drive cycle 3-4 times now.

Can I smog it with the pending code in the background? CEL is OFF.

This is a CA vehicle. Thanks!

rlx101

have you replaced any sensors or cat? why do you think you successfully resolved this?

P0420 - is essentially from cheap to expensive - bad O2 sensor, bad A/F sensor or bad cat (or any combination of these).

yeskay

with the CEL off how did you get the pending p0420 code. i had the same code and after i reconnected the battery aka clearing the codes no more CEL.

mre2000

Sorry been away for a couple of days. I haven't replaced anything relating to this code. I had a CEL situation for months that was outputting P0401 and P0402 EGR codes. I replaced a number of parts and finally cleared it. The pending code is not turning on the CEL, I also have not seen this before. My understanding is that after a couple more drive cycles, it will either turn on the CEL or clear the pending code. No O2 or cats replaced. Light hasn't returned but pending code hasn't cleared yet.

To be clear, I have no plans to replace any sensors or cats a) if the CEL isn't triggered or b) won't pass smog because of it.

My question is, I understand that I can run a smog test even if two monitors haven't completed yet, I only have one incomplete (CAT) and am wondering if the pending code will stand in the away of getting smog to run (not PASS, just run). Again, Im in CA

mre2000

UPDATE - car passed smog today. Still has the P0402 pending code but car will pass with one or two monitors not ready. Thanks for the replies!

Ichigo1287

generally when i see that code on most any car or truck its saying the cat has gone bad. although the code is thrown by the downstream o2 sensor that is because it is switching back and forth from rich to lean when it should not be at all only the front one should

donbryce

I'm pretty sure the bank 1 sensor is the one on the manifold next to the firewall. I get the same code on our '96 Camry, with the CEL coming on about 150 - 200km of sustained driving. We just reset it and carry on. Local mechanic's consensus is that this is common on Toyotas with OEM oxygen sensors and aftermarket cats. The cat on this car is relatively new, so it makes sense.

Mxkmster

Best thing for the pending it try running some premium fuel and add some isoprobyl alcohol through when you go to smog. The pending codes means that the fault happened once, normally it needs two continual key cycles to turn the MIL on. I run a aftermarket high flow cat for day to day use, but for smog time I put on my OEM cat. Its worth the effort in that you save a good cat.

Mxkmster

if you have a OBD 1 car, being prior to 96, you can check your o2 sensor read out from the main o2 sensor. The suboxygen sensor, behind the cat, will have half the movement back and forth of the main sensor. If almost no movement in voltage happens with the sub oxygen sensor then it be a good idea to replace that sensor. The voltage range is 0.1v to 0.9v.
If your car is OBD 2, after 96, then you can get a scan tool and connect it to the DLC connector and see that data.

LeX2K

Just as an FYI, ES300's were ODBII starting in 1994.