O2 Sensor Replaced Cel Won't Go Off!

[rubykey]

I took my 94 ES 300 to my trusted Toyota mechanic (independant but 75% Toyota only business) when CEL went on. It said to replace O2 sensor, which was done yet the CEL continues. I've been back 2 times and the codes reveal no problem. 10 miles later ....CEL. Said mechanic called Lexus who said they "always replace both O2 sensors when one is bad." My gas mileage has gone down to 20MPG from the usual 24MPG. I do use 87 or 89 octane since I don't notice a difference with 91.

IIt sounds like Lexes will charge some $900 or more??? to change O2 sensors, from what I'm reading on previous posts.

MY DILEMMA -- my mechanic is willing to put back the old O2 sensor and completely refund my money. I've known him for 20 years and he has always been fair and honest (not cheap though). Or he can put in the second O2 sensor (for a charge) as Lexus repair dept. suggested. He says however, if this does not solve the problem he will offer no refund, nor guarantee it will solve the problem.

MY QUESTION -- if CEL continues after changing both sensors with my mechanic I'd feel compelled to go to the Lexus shop. Could they then say " oh these O2 sensors are not genuine Lexus so of course they don't work?"

I know that Lexus and Toyota parts are interchangeable no? Does anyone know if using generic O2 sensors will trip the codes? Mechanic thinks that too could be the culprit. Any thoughts?

Thanks,

[cruznroadking]

Ask your mechanic what the trouble code is. When the check engine light comes on it can be several things. If your mechanic has the proper scan tool to perform the tests it should tell you which sensor is malfunctioning. Although on rare occassions both can go out on high mileage cars.

[SKperformance]

lexus doesn't change both o2 sensor for one failure.

That would be just dumb

[SKperformance]

Another member suggested cleaning your maf as the signal is wrong from it being dirty.

[steviej]

Could they then say " oh these O2 sensors are not genuine Lexus so of course they don't work?"

I know that Lexus and Toyota parts are interchangeable no? Does anyone know if using generic O2 sensors will trip the codes? Mechanic thinks that too could be the culprit.  Any thoughts?

Thanks,

←

yes they could say that and I know of instances where they have said that.

generic O2 sensors could be the culprit, yes.

you can get OEM O2 sensors on www.sparkplugs.com as an alternative.

Swaping sensors may confirm the problem sensor. For example:

If your code was P0135, then the O2 sensor at Bank 1 Sensor 1 is suspect. Swap this for the sensor at Bank 2 Sensor 1 (same place opposite side). Drive around for a while. If the CEL code changes to P0150, then the sensor is confirmed faulty.

steviej

[rubykey]

Thanks for the input. Yes the O2 sensor in (I think) Bank 1 was bad and an OEM sensor was put in. It did not come from Toyota, it came from whatever local distributer my mechanic uses. And yes it would be dumb to change both if only one is coming up as bad HOWEVER that's what the tech at Oakland Lexus said they do. I don't trust the crooks at Oakland Lexus. That's why I'm checking in here. My mechanic has been fixing cars for 30+ years way before these computers confounded the car repair scene. He's never advised me to do something just to make a buck, and is offering to refund my money and put back the old O2 sensor because he's coming up empty with ideas since the codes are still reading bad O2 sensor on the one that has been replaced. He admits it did not come from Toyota, so perhaps that's why it's not happy with the O2 sensor. I'll pass on the info about cleaning the maf.

[rubykey]

Thank you for your input. Here's the result. I decided to go to the dealer after having my mechanic refund my $$ and replace the old O2 sensor. The code was P0135 and according to the Concord dealer my mechanic replaced the wrong sensor. So I paid a little more but the problem appears to be fine, and i had a good experience with that dealer. I did pass on the good tips from here but Mr. Mechanic wasn't interested. Thanks you all. It really did help as I too thought it was dumb to replace both sensors if only one is coming up bad.

[SKperformance]

glad that you got it sorted