I think it's wise for the upstream o2 sensors (before the catalytic converters)

My fuel economy went up after I put in new sensors. Not much, but around 2 mpg. After a certain point, they become less accurate. My concern was less about the savings the the pump, and more about an imprecise mixture of air/fuel. In this case, it looks like the engine was running a bit rich with the old O2 sensor. More rich=more wear on the engine.

Most O2 sensor companies recommend replacement as part of a tuneup, just like you would change your spark plugs even if they weren't throwing codes after a certain mileage.

I have around 140k miles, and the cost war around $120, so about 2 tanks of gas.

I wouldn't touch the down stream (after cat) sensors unless they were throwing codes, they exist as a sort of "pass/fail" for emissions testing, it doesn't "tell" the engine to make changes on the fly. And even if you were getting codes on the downstream sensors, I'd probably look into getting a "cheater" plug that fooled the sensor before I replaced the cats and sensors.

 

Hmm interesting. Im gonna look into doing the replacements soon. I'm pretty good at DIY but will have to pre-inspect the conditions beforehand to make sure have all the necessities for the job. What is this cheater plug thingy?

 

Sorry i havent been online for a few days....thanks for all the help!

I got under the car, and saw that the o2 sensor was bent almost 45 degrees! Whatever i hit on the freeway bent it, and tore up some of that heat shield next to the sensor.

It took a few days for the light to come on though. I ordered an universal Denso and plan on hitting it out after my vacation

 

A cheater plug was just my name for them, but you can either put an electrical resistor in between where the O2 sensor goes to the harness, or you can space the O2 sensor away from the exhaust so it "trick" the ECM into believing everything is okay with the catalytic converter.

They're used for the DOWNSTREAM O2 sensor (after the cat converter)

The downstream oxygen sensor is basically for the purpose of emissions testers to let them know something is wrong with the catalytic converter. It's a pass or fail sensor, it doesn't tell the car to adjust fuel delivery.

 

Ok gotcha! but would you need to "cheat" if your cat is still good or its just for those cases where you do have a bad CAT?

 

No need unless the downstream O2 sensors went out or the catalytic converter had lost its efficiency to the point it was setting off a "Check Engine" light.

If you're not getting any sort of codes, leave it be. Your car won't run any better replacing the downstream O2 sensors with new ones.

There's always the "right way" to fix it if you're getting those codes, but you're likely looking at a new catalytic converter set up (around $1,500 through a dealership) and 2 new O2 sensors. Most likely all of the above if you've got well over 100k miles on the car. If you're not doing the work yourself, you're looking at about $2,000 worth of work to get rid of that check engine light for the emission tester.

Or a $12 spacer plug.

 

Please make sure that if your car has AFR sensor (air fuel ratio) then you replace it with an AFR and if you have oxygen sensor then r,eplace it with oxygen sensor since signal detection circuitry inside the ECM looks for a specific voltage range for feedback signal. If the feedback signals are different then ECM will throw cel light and could also lead to damaging the ECM. Thanks

 

Hi,
I'm also getting two codes, P0138 and P0158, I had some problem with the harness in engine bay and some wires were patched after they were frayed. It's a sc430, yr2002
P0138 is high voltage in the B1S2 circuit. Would you happen to have the ecu resistance based Troubleshooting steps are same as mentioned above for diagnosing P0158
Greatly appreciate your help in advance
Thanks

 

my LS 430 with 84,000 miles just needed one sensor replaced. Parts and labor and tax totaled about $550. That seems high, but my warranty covered most of it.

 

I just order O2 sensor today for our '06 with 65K on it,

 

I think up until now that is record for the earliest reported O2 sensor failure in our cars, but my 2005 LS430 with 60,000 miles just threw the P0031 code!
This is a most dubious honor.

 

Get some beers, read some tutorials, replace, drink more beer. You don't even need a garage, and the tools to do the job cost like $30. Plus $15 for the beer. I prefer Natty Ice.

 

Makes me curious what the usual drive distances are? Short runs or does the car get to see some highway at 15+ miles?

 

All of the above.

 

In 2010, I had a P0155 (the heating element inside my front right O2 sensor had failed) at 51884 mi - see my post #11 above from 2013. Now my LS430 is at 17 years in service, 102,000 mi (164,000 km), my 3 other O2 sensors are still originals. I assume the one that failed must have had a manufacturing defect.

My weekly driving is short distances (4-8km per engine-on cycle).