Check Engine Light -- 2001 Prius

gippah · 10-01-2007, 04:33 AM

I have a 2001 Prius and the 'check engine' light came on yesterday, about a day after filling the tank up. The tank was still on full. I'm NOT referring to the warning triangle that can come up on the main screen, but the engine light in the cluster.

On most cars, the 'check engine' light usually means an emissions or transmission problem. Most notably the light is triggered when filling the car with bad gasoline or leaving the gas cap off / having it on too loosely.

As with other cars, the definition of what this light means on the Prius is obscure in the manual. Is this light treated the same as other cars -- being an emissions problem -- or could there actually be something wrong with it?

The car is performing just as it has been, though as I said I did just fill it up with gas.

Toyota likes to charge $90 to run any diagnostic so I'd prefer to have a feel for what the problem is before I take it in and ask them.

gippah · 10-01-2007, 10:42 AM

I brought it in to a Toyota dealership and they are saying that the catalytic converter has gone, with a replacement costing $2100.

This seems kind of weird to me that it would go so quickly, one would expect a part like this to have a more gradual failure, barring physical damage or abuse.

The last few times I have taken either of my Toyotas to Toyota dealerships I haven't been very impressed, it seems to me that they just hook it up to their computer and don't do any real troubleshooting beyond that. Since I've seen this at multiple dealerships now I'm thinking this is what Toyota is telling them to do.

Anyway, I'm digressing. Assuming the more likely scenario of me just having a bad tank of gas, how long will it take for the 'check engine' light to clear?

gippah · 10-01-2007, 04:30 PM

I got a code from the dealership, I'm hoping this is the right diagnostic code and it will help someone here isolate this better:

P0420

gippah · 10-03-2007, 11:09 AM

So none of the techies here have any insight on this? Will a universal catalytic converter work on the Prius? What else could it be with this error code, as I think it's a safe assumption that the dealership didn't check a single thing?

**efusco** · 10-03-2007, 11:13 AM

We've only got a handful of 1st Generation owners here so good info on tech issues might be harder to come by. Have you checked the Yahoo! 1st Gen. Prius site or the Prius tech site at Yahoo!?

gippah · 10-03-2007, 11:21 AM

Well if no one knows, and the check engine light doesn't disappear after a new tankful of gas or two, I'll just get a universal catalytic converter for it.

$100 vs. $2200 is a pretty huge difference.

Thanks for the direction.

**efusco** · 10-03-2007, 11:25 AM

I'd check the sites I recommended before wasting $100 on a universal Cat. I suspect that the emissions controls require some pretty specific things and that the Cat is part and parcel to that proper operation. While the universal may work, I suspect it won't eliminate your CELs and may even inhibit proper operation of the car.

I don't know this for fact, but knowing the Prius I'm suspicious of that and it's definately worth asking around where the majority of folks most familiar with the Gen 1 hang out.

galaxee · 10-03-2007, 11:42 AM

cripes. yes, we all know nothing. you seemed to have the issue figured out but ok

this is what i can dig up on TIS, but the expert is busy at home and i'm at work.

DTC P0420 Catalyst System Efficiency Below Threshold

Catalyst Deterioration Monitor Description
MONITOR SUMMARY
The ECM compares the output waveforms from the oxygen sensors installed on the front and rear of the
catalyst to determine if the performance of the catalyst has decreased beyond specified limits. The waveforms
from each sensor continue changing from rich to lean, lean to rich. When the catalyst functions normally,
the output waveform cycle of the rear oxygen sensor is much longer than that of the front oxygen sensor.
When the output waveforms from the front and rear oxygen sensors change in the similar cycle, the ECM
determines that the performance of the catalyst has decreased below specified limits. The ECM will illuminate
the MIL and a DTC is set.

so it may be gradual but you hit the threshold when the CEL kicked.

gippah · 10-03-2007, 11:49 AM

Yes, you're not saying anything unknown by posting that.

However, the P0420 code isn't triggered by the CC itself, but it is instead triggered by trying to match whether or not the sensors in front of it and behind it are giving expected readings. So, of course, the problem could be the sensors. I'm hesitant to believe that the mechanic troubleshot anything. For a $2200 repair, of course I have to be shown by the mechanic who worked on the car exactly what he looked at. Toyota dealerships aren't set up to do this, however, customers are never face to face with any of the mechanics.

The real question is, how will a universal CC affect the Prius? I can tell you that there is a 0% chance that I am going to spend $2200+ tax on a catalytic converter when I can get one for $50 and a new set of universal sensors for another $50.

**efusco** · 10-03-2007, 11:57 AM

You might be able to pick up a salvage Cat off a 1st gen complete with sensors for pretty cheap...I realize $2200 is dang high, but I can't imagine the salvage are that much, maybe more than the $100 universal, but to be sure that you've solved the issue it may well be worth a couple hundred extra.

10-03-2007, 11:25 AM	#7
efusco Troll Slayer Join Date: Nov 2003 Location: Nixa, MO Posts: 17,238 My Car: 2004 Prius Model: Package: #9 Thanks: 49 Thanked 249 Times in 148 Posts Friends: 37	I'd check the sites I recommended before wasting $100 on a universal Cat. I suspect that the emissions controls require some pretty specific things and that the Cat is part and parcel to that proper operation. While the universal may work, I suspect it won't eliminate your CELs and may even inhibit proper operation of the car. I don't know this for fact, but knowing the Prius I'm suspicious of that and it's definately worth asking around where the majority of folks most familiar with the Gen 1 hang out. __________________ Evan E. Fusco, MD "It's a damn poor mind that can only think of one way to spell a word." -Andrew Jackson

10-03-2007, 11:42 AM	#8
galaxee resident lab rat Join Date: Mar 2005 Location: boilermaker territory Posts: 9,675 My Car: 2005 Prius Model: N/A Package: #5 Thanks: 0 Thanked 94 Times in 37 Posts Friends: 26	cripes. yes, we all know nothing. you seemed to have the issue figured out but ok this is what i can dig up on TIS, but the expert is busy at home and i'm at work. DTC P0420 Catalyst System Efficiency Below Threshold Catalyst Deterioration Monitor Description MONITOR SUMMARY The ECM compares the output waveforms from the oxygen sensors installed on the front and rear of the catalyst to determine if the performance of the catalyst has decreased beyond specified limits. The waveforms from each sensor continue changing from rich to lean, lean to rich. When the catalyst functions normally, the output waveform cycle of the rear oxygen sensor is much longer than that of the front oxygen sensor. When the output waveforms from the front and rear oxygen sensors change in the similar cycle, the ECM determines that the performance of the catalyst has decreased below specified limits. The ECM will illuminate the MIL and a DTC is set. so it may be gradual but you hit the threshold when the CEL kicked. __________________ black 2005 prius, a few mods that make me happy g: class of '09 in intense science DH: class of '09 in medical equipment hoping to discover the 'reward' part of the sacrifice-reward cycle soon!

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10-01-2007, 04:33 AM	#1
gippah Senior Member Join Date: Apr 2006 Location: Austin, TX Posts: 105 My Car: Model: Package: Thanks: 0 Thanked 0 Times in 0 Posts Friends: 0	I have a 2001 Prius and the 'check engine' light came on yesterday, about a day after filling the tank up. The tank was still on full. I'm NOT referring to the warning triangle that can come up on the main screen, but the engine light in the cluster. On most cars, the 'check engine' light usually means an emissions or transmission problem. Most notably the light is triggered when filling the car with bad gasoline or leaving the gas cap off / having it on too loosely. As with other cars, the definition of what this light means on the Prius is obscure in the manual. Is this light treated the same as other cars -- being an emissions problem -- or could there actually be something wrong with it? The car is performing just as it has been, though as I said I did just fill it up with gas. Toyota likes to charge $90 to run any diagnostic so I'd prefer to have a feel for what the problem is before I take it in and ask them.

10-01-2007, 10:42 AM	#2
gippah Senior Member Join Date: Apr 2006 Location: Austin, TX Posts: 105 My Car: Model: Package: Thanks: 0 Thanked 0 Times in 0 Posts Friends: 0	I brought it in to a Toyota dealership and they are saying that the catalytic converter has gone, with a replacement costing $2100. This seems kind of weird to me that it would go so quickly, one would expect a part like this to have a more gradual failure, barring physical damage or abuse. The last few times I have taken either of my Toyotas to Toyota dealerships I haven't been very impressed, it seems to me that they just hook it up to their computer and don't do any real troubleshooting beyond that. Since I've seen this at multiple dealerships now I'm thinking this is what Toyota is telling them to do. Anyway, I'm digressing. Assuming the more likely scenario of me just having a bad tank of gas, how long will it take for the 'check engine' light to clear?

10-01-2007, 04:30 PM	#3
gippah Senior Member Join Date: Apr 2006 Location: Austin, TX Posts: 105 My Car: Model: Package: Thanks: 0 Thanked 0 Times in 0 Posts Friends: 0	I got a code from the dealership, I'm hoping this is the right diagnostic code and it will help someone here isolate this better: P0420

10-03-2007, 11:09 AM	#4
gippah Senior Member Join Date: Apr 2006 Location: Austin, TX Posts: 105 My Car: Model: Package: Thanks: 0 Thanked 0 Times in 0 Posts Friends: 0	So none of the techies here have any insight on this? Will a universal catalytic converter work on the Prius? What else could it be with this error code, as I think it's a safe assumption that the dealership didn't check a single thing?

10-03-2007, 11:13 AM	#5
efusco Troll Slayer Join Date: Nov 2003 Location: Nixa, MO Posts: 17,238 My Car: 2004 Prius Model: Package: #9 Thanks: 49 Thanked 249 Times in 148 Posts Friends: 37	We've only got a handful of 1st Generation owners here so good info on tech issues might be harder to come by. Have you checked the Yahoo! 1st Gen. Prius site or the Prius tech site at Yahoo!?

10-03-2007, 11:21 AM	#6
gippah Senior Member Join Date: Apr 2006 Location: Austin, TX Posts: 105 My Car: Model: Package: Thanks: 0 Thanked 0 Times in 0 Posts Friends: 0	Well if no one knows, and the check engine light doesn't disappear after a new tankful of gas or two, I'll just get a universal catalytic converter for it. $100 vs. $2200 is a pretty huge difference. Thanks for the direction.

10-03-2007, 11:49 AM	#9
gippah Senior Member Join Date: Apr 2006 Location: Austin, TX Posts: 105 My Car: Model: Package: Thanks: 0 Thanked 0 Times in 0 Posts Friends: 0	Yes, you're not saying anything unknown by posting that. However, the P0420 code isn't triggered by the CC itself, but it is instead triggered by trying to match whether or not the sensors in front of it and behind it are giving expected readings. So, of course, the problem could be the sensors. I'm hesitant to believe that the mechanic troubleshot anything. For a $2200 repair, of course I have to be shown by the mechanic who worked on the car exactly what he looked at. Toyota dealerships aren't set up to do this, however, customers are never face to face with any of the mechanics. The real question is, how will a universal CC affect the Prius? I can tell you that there is a 0% chance that I am going to spend $2200+ tax on a catalytic converter when I can get one for $50 and a new set of universal sensors for another $50.

10-03-2007, 11:57 AM	#10
efusco Troll Slayer Join Date: Nov 2003 Location: Nixa, MO Posts: 17,238 My Car: 2004 Prius Model: Package: #9 Thanks: 49 Thanked 249 Times in 148 Posts Friends: 37	You might be able to pick up a salvage Cat off a 1st gen complete with sensors for pretty cheap...I realize $2200 is dang high, but I can't imagine the salvage are that much, maybe more than the $100 universal, but to be sure that you've solved the issue it may well be worth a couple hundred extra.