lorddeceiver

i got a 98 se with about 45k on it. a few months ago my engine service light went on indicating my front O2 sensor went bad (according to the dealer), several weeks later, the light went on saying the real O2 heating sensor is bad, too. i got suspicious of the situation and didn't replace the real sensor. the light is on again just today, and i am pretty sure this time it is the same problem... i checked up the nhtsb's service bulletin and there's a case of rear o2 sensor problem...

my question is: is the dealer supposed to fix this for free since it is an identified issue? how do i tell if this is a faulty ecu problem or a real sensor failure? the sensors are failing one by one, what is going on here? i noticed my mpg has gone down quite a bit lately.... help!!!!!

Daniel B. Martin

After the warranty expires repairs are the owner's responsibility.

Daniel B. Martin

Faulty Oxygen Sensors are a common problem. Faulty Engine Control Modules are rare.

Daniel B. Martin

Some Nissan owners report Oxygen Sensor failures as early as 30K miles. In my own experience they last much longer than that.


There are two degrees of failure.

1) The Oxygen Sensor is "dead".
The signal from the Oxygen Sensor is outside the normal range, or completely absent. The Engine Control Module (the computer) turns on the Malfunction Indicator Light and stores one or more Diagnostic Trouble Codes. This failure mode is obvious because of the dashboard warning light.

A dead Oxygen Sensor is a severe failure and should be repaired promptly.

2) The Oxygen Sensor is "tired".
The Oxygen Sensor still works but it responds slowly to changes in the oxygen concentration in the exhaust stream. There is no MIL or DTC. This failure mode is less obvious. The symptoms are increased fuel consumption, decreased engine power, and a feeling of sluggishness. The throttle response is not crisp, like it was when the car was new. An Oxygen Sensor may become tired due to high mileage or being "poisoned" by exposure to various substances including leaded fuels, anti-freeze, anti-seize, RTV sealants, and the residue of burned engine oil. A "tired" Oxygen Sensor is still doing its job, but not performing well.

A tired Oxygen Sensor is not a severe failure and the car may be operated safely.


You may have your Oxygen Sensor(s) tested. There are electronic testers made for this specific purpose. In addition, a technician with an automotive oscilloscope can test Oxygen Sensors. The signal from a healthy sensor varies from a low threshold (around 0.2 volts) to a high threshold (around 0.8 volts), and it sweeps back and forth between those extremes about 10 times per second. If the scope trace shows the Oxygen Sensor signal failing to reach either extreme, or oscillating between them at a frequency slower than 10 cycles per second, that is evidence of a "tired" sensor.

I've read that a bad Oxygen Sensor can sometimes be rejuvenated by removing it, clamping it in a vise, and heating the sensing tip red hot with a propane torch. This is said to burn off a crust of deposits which interfere with its operation. I've never tried this torch trick myself, so cannot vouch for it's effectiveness. If you have a sensor which is already dead, you have little to lose.

For more information about Oxygen Sensors see:
http://www.volksparts.com/o2sensors.htm
http://members.aol.com/carleyware/library/o2sensor.htm

lorddeceiver

daniel, thanks for your quick response! the dealer didn't tell me whether my sensors were tired or dead... they just said it is faulty. i guess i'd ask them next time----should i mention the service bulletin case? do they even care about it?

vmok

Depending on your state, check the warranty book that came with the car. I think the emissions components are covered for a certain period of time/mileage, and it may even depend on the state that you live in. The emissions components are often listed separate of the powertrain or bumper to bumper warranties...

-V

Sonic

What mileage is your car? The oxygen sensor issue is a coomon one at dealerships. YOu should ask around dealerships to see if they are willing to replace the O2 sensor free of charge. Several org members have done this.

Daniel B. Martin

Yes, do mention the Technical Service Bulletin. That will, at least, identify you as a customer who is aware and informed.

If you like to do your own "wrenching" you might want to replace the Oxygen Sensors yourself. This might be the economical course of action.

Daniel B. Martin

Some owners of '96 Maximas received new Oxygen Sensors at no cost because Nissan had/has a "campaign" replacement program. I don't know if your '98 is covered.

Ask your dealer about a campaign repair. Your car might qualify for campaign #3182 and you could get this repair work done for free. See http://216.122.219.59/forums/showth...1131#post361131

lorddeceiver

my car is 44k, just out of the original 36k warranty. i checked the book, and only california warrants emission parts over 36k. so i guess regardless a technical service bulletin item, i'd have to pay out of my pocket this time... thank you all for your help!!! if you have more suggestions, let me know please!!!

lorddeceiver

daniel,
once again thank you for the input----however i was unable to get to the link you provided... any clues? sorry for the repeated bugging...

jerome

Daniel B. Martin

http://216.122.219.59/forums/showthread.php?s=&postid=361131#post361131