So Is The Mechanic Confused? Or Is It Me?

[xxbulovax91xx]

So after having no luck figuring out the Check Engine Light, I finally took my 95 ES300 to a repair facility where the service writer told me that the tech thought my catalytic converter was going bad and it wasn't getting hot enough to send a proper signal to the o2 sensor located on the cat, and that's why my Check Engine light came on from a Code P0170 (Fuel Trim Malfunction).

Later, though, I talked to the tech himself who said he thought it may have been a faulty Mass AirFlow Meter, and thats why the Code.

So I think to myself.... Well if my cat were going bad, would I have passed smog just fine at the same place in January?

But also, if the MAF was faulty, wouldn't I experience a rough idle or poor performance as a result of it?

Just looking for any thoughts/ ideas.

[xxbulovax91xx]

*sigh*.... No help?

[Toysrme]

P0170 is a fuel trim malfunction for the "rear bank aka bank 1 aka right hand bank". Since you're not pulling a fuel trim malfunction for bank 2, I bet it's the rear oxygen sensor. Test/Replace that. & if it tests OK, then check the fuel injectors / spark plugs on that bank.

I think it's just the o2 sensor. It's a '95, it's about that time... You can pass emessions with a dead one as long as it's not just *really* dumping fuel in. Which it can't really do just off a ead o2 sensor.

If the cat were bad, you'd have a hard time passing emessions, but it can be done, provided you're getting really good combustion. If the cat were bad - you'd get an o2 reading from the *post cat* o2 sensor. Not one before the cat (which is what you have). ;)

All roads lead to Rome. Test/replace the o2 sensor on the rear manifold.

[xxbulovax91xx]

So you think definately not the Mass Air Flow Sensor, as the tech says? I am doubting the tech's diagnostic, but is it possible a faulty mass air flow sensor could do it?

P0170 is a fuel trim malfunction for the "rear bank aka bank 1 aka right hand bank". Since you're not pulling a fuel trim malfunction for bank 2, I bet it's the rear oxygen sensor. Test/Replace that. & if it tests OK, then check the fuel injectors / spark plugs on that bank.

I think it's just the o2 sensor. It's a '95, it's about that time... You can pass emessions with a dead one as long as it's not just *really* dumping fuel in. Which it can't really do just off a ead o2 sensor.

If the cat were bad, you'd have a hard time passing emessions, but it can be done, provided you're getting really good combustion. If the cat were bad - you'd get an o2 reading from the *post cat* o2 sensor. Not one before the cat (which is what you have). ;)

All roads lead to Rome. Test/replace the o2 sensor on the rear manifold.

[monarch]

The oxygen sensor(s) ahead of the catalytic converter need to be changed by 100-150K miles even if they aren't responsible for the P0170 check engine light, but most of the time they are. Delaying changing the oxygen sensors is a walet emptying proposition because it means you're car's fuel economy if off by 2 MPG and the excess gasoline is shortening the life of your catalytic converter and EGR valve. Another cause of a P0170 is old spark plugs or aftermarket spark plugs. The MAF sensor is generally troublefree unless you have been using an aftermarket air filter.

[mburnickas]

P0170 is a fuel trim malfunction for the "rear bank aka bank 1 aka right hand bank". Since you're not pulling a fuel trim malfunction for bank 2, I bet it's the rear oxygen sensor. Test/Replace that. & if it tests OK, then check the fuel injectors / spark plugs on that bank.

I think it's just the o2 sensor. It's a '95, it's about that time... You can pass emessions with a dead one as long as it's not just *really* dumping fuel in. Which it can't really do just off a ead o2 sensor.

If the cat were bad, you'd have a hard time passing emessions, but it can be done, provided you're getting really good combustion. If the cat were bad - you'd get an o2 reading from the *post cat* o2 sensor. Not one before the cat (which is what you have). ;)

All roads lead to Rome. Test/replace the o2 sensor on the rear manifold.

I would agree test / replace is a good thing. I think here the word "test" sticks out since you can save some $$$ if you do a quick test and see what you have. Or use a OBD 2 scanner ans see what it tells you on volts and time. A scanner will also tell you spark plugs issues, fuel flows etc. That is why I bought one..I love that little red box!! LOL

If they (02) are bad then replace as you stated. I guess I am just a cheap guy or like to know what I am replacing is the issue.

[JPI]

What is the voltage reading for MAF at idle and 2000rpm? Also Please provide us the long term fuel trim reading. If you are able to answer these questions, I would be able to help you out.

JPI

[godfather18]

What is the voltage reading for MAF at idle and 2000rpm? Also Please provide us the long term fuel trim reading. If you are able to answer these questions, I would be able to help you out.

JPI

Where do you get a scanner like that?