Check engine light on 99 limited no symptoms pulling code for bad catalytic conv.?

[Ctimesthree]

Hello

I just bought a 1999 Limited with 188,000 orig. miles. This is after some jerk totaled my 96 with 230,000 miles that was still running like a champ up until then. Heres the issue...car runs great but after a week the check engine light pops on randomly. Of course. After being told at AutoZone they couldnt scan my car (im in california) a nice mechanic who happened to be there had his OBD11 and hooked it up and said it looked like the catalytic converter and possible temp. Gage. I'm not overheating, no sulphur smell and I'm getting good mileage. I'm just hoping to gain some insight on if it's ok to keep driving or if it's possible it's just an O2 sensor? Being a girl I get both ends of the pool as far as people trying to rip me off and those nice enough to stop what theyre doing to help a stranger...figured this would be a great place to get some unbiased opinions before I have to take it in...

 

[stevec5000]

The cat shouldn't be bad yet unless it's suffered some physical damage or the engine has been leaking fuel, antifreeze or oil into it and it got contaminated somehow so it's probably just a bad O2 sensor. There is one in front of the cat right where the exhaust first comes out of the engine to indicate the fuel to air mixture the engine is running at or how rich it is, and a second one behind the cat that is supposed to read lower to show the cat is working to reduce emissions. You should be able to use a ScanGauge on the OBDII connector to check them. The front one should indicate about 0.5 volt when the engine is warmed up and running with the correct mixture and the back one should read lower, almost zero. In your case the back one must be reading higher but that could be because it's bad. You could have someone reverse their positions to see if the back one works in the front position or if it's bad and you can also take it off the vehicle and check it on the bench with propane. Not having a Scangauge you can also check them for 0.5 volts with a DVM but only after they warm up to 700 degrees and start working. The cat is easy to check by eye if you have someone take it off and examine it. The ceramic honeycomb material inside should be clean and free of cracks or contamination. If there is a big dent in the outside that would be bad also.
It shouldn't hurt to keep driving it unless you have to take it in for an emissions test but I wouldn't drive it if there is any indication of overheating.

I guess you probably can't do any of this yourself but you will at least know what to look for to tell if you are getting ripped off.

 

[jkoni426]

It sounds like a bad cat to me because the ecu has to detect the malfunction over a few drive cycles, so that would be why it's taking a week to show up. But it's anyone's guess unless you know the exact codes that are coming up. If you know them post em up and we can help better. Not sure why autozone couldn't give em to ya for free...

 

[Ctimesthree]

Thanks so much for the replies...yea I was kind of put off by them telling me no too...something about CA not allowing them to do it since they passed something 4 years ago...Mmmhmm I'm sure :-/ regardless the nice dude that did go out of his way to lend a hand was quite helpful. My guys family owns a machine shop and he's more mechanically inclined than not so luckily I'm not completely screwed. If it is the cat then I know the deal on that ESP here in sunny CA. I completely spaced on asking the codes. With my last 4runner I had a misfire on my 6th cylinder and a friend of ours read the codes so I was able to notify the shop that ended up fixing it. I'm taking it tomorrow to have it ran again so I know for sure. It's driving perfectly with no sign of overheating however, the car is new to me so I'm kind of handicapped. There was also another code about perhaps a temp gave or temp sensor? That I'm not familiar with so I'm not sure what that means. The guy who ran them for me said the actual gage may need to be replaced...again, not certain on that. I should know more tomorrow but I'm kind of at a loss....

 

[TheDurk]

I'm going to guess you threw a P0125 which comes up as something like: Insufficient Coolant Temperature For Closed Loop Fuel Control. It is usually your front O2 sensor, despite the legend.

We really need the exact codes to help you.

 

[02adventurer]

I just had the same code come up, ended up being the upstream cat, 1100 bucks for the new one, and after installation i drove it 10 or 12 times letting it do a total engine cycle of hot to cold. after that the light went away... pissed it had to be an 1100 dollar part, only reason i did it was because i had to get it smogged in a few days

 

[stevec5000]

I'm going to guess you threw a P0125 which comes up as something like: Insufficient Coolant Temperature For Closed Loop Fuel Control. It is usually your front O2 sensor, despite the legend.

We really need the exact codes to help you.

Wouldn't that be more likely due to a bad thermostat or temp sensor? Also it's possible the O2 sensors aren't heating up enough to work because their heaters aren't getting power. Could be just a blown fuse. I would check all the simple stuff first like thermostat, fuses, etc before letting anyone start taking things apart.

 

[TheDurk]

Wouldn't that be more likely due to a bad thermostat or temp sensor? Also it's possible the O2 sensors aren't heating up enough to work because their heaters aren't getting power. Could be just a blown fuse. I would check all the simple stuff first like thermostat, fuses, etc before letting anyone start taking things apart.

Yeah, that's what you'd think. It has something to do with the ECU getting a bad signal from the O2 sensor that convinces it the temp sensor is wrong. Look it up in the FSM. None of the stuff you mentioned is even on the list of causes. Sometimes it IS the heaters, but they have their own codes, usually P1135 on later models. The FSM says always do the other codes first.

So you do what you want, I'll follow the Factory Service Manual. Lots of people have wasted time and money on thermostats and temp. sensors, you wouldn't be the first.

http://www.ncttora.com/fsm/1996/SIL/techinfo.toyota.com/ileaf/02toyrm/02toypdf/02rmsour/2002/024runne/di/eg5vzfe/cip0125o.pdf