2001 Celica GT 1zz CEL PO420 - Toyota Nation Forum : Toyota Car and Truck Forums

pwm72 · 04-10-2011, 08:56 PM

I have a 2001 Celica GT and the CEL just came on. Went to Autozone and had the code read (PO420) - they said it could be O2 sensor or bad catalytic converter. Is there any way to narrow it down before I just start buying parts to replace? Car has 140,000+ and runs great...surprisingly one of the few that doesn't seem to burn oil!

Any thoughts on the PO420 diagnosis?

Thanks
Paul Manuel

RobMilkshakes · 04-11-2011, 06:34 AM

Do you have any other issues like the engine not coming up to temperature?

luisantoniof · 04-12-2011, 11:37 AM

I have the same issue and my car is about the 150K mark. I don't have any issues with the engine either it runs perfect. I don't think there is a way of knowing unless the car starts acting weird. I did nome research online and found out that the most common reason for the code is the upstream O2. I wouldn't worry too much (I don't) about it unless your car starts to act funny. Oh by the way I might be wrong and maybe I am destroying my car with out knowing, so if anybody has any different information please post asap

RobMilkshakes · 04-12-2011, 12:12 PM

It's a good idea to replace your oxygen sensors anyway, as it can, in the long run, improve your fuel economy and if your o2 sensor is completely bad the ECU will overcompensate and essentially dump fuel into the engine... which will degrade your cat farther and essentially necessitate a replacement.

This code will cause a problem when you have your emission tests as it will automatically fail with a CEL, and if the catalyst completely breaks down the cat could become clogged and cause performance issues.

The code sometimes can be tripped by a faulty coolant temp sensor or a malfunctioning thermostat but those are rare.

pwm72 · 04-12-2011, 09:34 PM

Thanks for the replies...the car does not seem to be getting warm...temp stays mid way on the gauge. This is actually my daughters car, so I would prefer to get it fixed rather then just having her driving around with the CEL on.

So it is most likely the upstream O2 sensor? I have not been under this car yet, but I imagine it is not to hard to locate?

Bitter · 04-12-2011, 10:02 PM

replace upstream sensor (was due at 90K miles), replace thermostat and coolant (due at 100K), replace cat (due now), and possibly the down stream sensor (due around 90K, but last longer due to less heat)

pwm72 · 04-13-2011, 05:58 AM

Thank you. Assuming this stuff is relatively easily replaced by the average owner, what should I expect to pay for a cat/O2 sensors?

RobMilkshakes · 04-13-2011, 07:00 AM

The cat should run about $215 for a direct fit replacement, but double check your local prices as they can vary a bit. O2 sensors will probably run ~$80 a piece.

pwm72 · 04-13-2011, 09:43 PM

Quote:

Originally Posted by RobMilkshakes

The cat should run about $215 for a direct fit replacement, but double check your local prices as they can vary a bit. O2 sensors will probably run ~$80 a piece.

Thank you. I am just up the road from you in Cecil County.
That price you suggest, is that an aftermarket cat or a Toyota piece? Are the aftermarket cats worthwhile?

Thanks again!
Paul

RobMilkshakes · 04-14-2011, 07:18 AM

That was the price for an aftermarket unit. The toyota price would be much higher. From what I've read, supposedly aftermarket cats have less catalyst than OEM would. That being said though, I've personally never heard of or seen any issues with after market converters myself so its something you'll have to make a decision on. The price I gave was a Walker price, depending on where you go, the price could vary a little bit but walker carries a 5 year warranty.

Its nice to see another person from MD here, not too many floating around these forums.

pwm72 · 04-14-2011, 09:20 PM

Thank you for your responses. Maybe I will see you around at some point.

taorge · 05-05-2011, 01:41 PM

upstream o2 is really easy to replace...i paid $65 for mine on amazon.com after autozone wanted 85...also had p0420 code...and after replacing both o2s i gained 100miles/tank

A_Ninja_Racer · 01-07-2012, 10:29 PM

Quote:

Originally Posted by pwm72

Thanks for the replies...the car does not seem to be getting warm...temp stays mid way on the gauge. This is actually my daughters car, so I would prefer to get it fixed rather then just having her driving around with the CEL on.

So it is most likely the upstream O2 sensor? I have not been under this car yet, but I imagine it is not to hard to locate?

Hey did you ever replace the Upstream O@ sensor? Did That Fix The CEL? I got the same thing going on.

RobMilkshakes · 01-08-2012, 10:48 AM

Depending on your milage a replacement would likely be due anyway. You can test an oxygen sensor, but for check engine lights, there is rarely one definite thing that will trigger any one specific code.

A_Ninja_Racer · 01-08-2012, 12:49 PM

Quote:

Originally Posted by RobMilkshakes

Depending on your milage a replacement would likely be due anyway. You can test an oxygen sensor, but for check engine lights, there is rarely one definite thing that will trigger any one specific code.

Well after reading a few other posts I decided to go forward with the up stream O2 sensor. I took it down to the local parts store and had the code cleared and it royalty changed the idling characteristics. I think this fixed the issue. Now I don't have a tag on the car yet so I pretty much drove straight back to the house. Maybe 2 miles so we will have to see in the future if it is truly fixed or not. I also changed the oil & air filter and spark plugs. The next thing on my list is artifacts all the way around.