Just boughtin 240SX, check engine light question

[dzzydmb]

Just bought a 1994 240SX convertible on Thursday and the check engine light is on. What is the likelihood this is because of an oxygen sensor that needs changing? How many oxygen sensors does this car have? What should I expect to pay for a replacement sensor(s) and how difficult is the change?

If it's not the oxygen sensor, what else might make the oxygen sensor come on? I have access to a code reader device...where does it connect to the car?

Car has 151K miles; only thing not stock is the exhaust. Bodywork is in remarkably good shape considering its age and the car drives GREAT.

This car seems to be a nice one for what I paid ($2000) and I also would like to ask, was that a good price? What do these cars typically sell for? I look forward to any help with it I can get through this forum, including the questions I have asked and any general heads-up advice y'all can offer.

Thanks in advance!
Modified by dzzydmb at 10:00 PM 1/28/2010

[speedeast]

Check engine lights are not always the Oxygen Sensors, actually I've never had one for an Oxygen Sensor. It was always for something like a misfire, detonation sensor, or vacuum or evap system leak. Take it to your local Advance, Auto Zone, Pep Boys, O'Reilly's... whatever you got and ask them to hook it up. Usually under the dash on the driver's side. I'm not 100% sure if the '94 has one, but I'm pretty sure it does... I think those have a standard 2 oxygen sensors fyi, and they're easy to change if you've got tools and a jack/jack stands. Then again if you don't have tools it's pretty much impossible.

And for $2000 it needs to be in remarkably good shape.

If you can't hook it up to the OBD II, then start with simple things to diagnose like spark, compression, fuel pressure, alternator. And check all your fuses and change all your filters. Good luck!

[r3v_v3ng3]

use the search button and you'll find a way to retrieve the code(s) its as easy as finding your ecu and turning the knob and count the cel flash

[Wc240]

you wont be able to hook up your code reader. im assuming its an obd2 code reader and your car is not obd2

[dzzydmb]

Got the code reader and it said it was the oxygen sensor. Guy said it had to do with the exhaust temperature. Oh and it turns out the car has California emissions.

Guy gave me a diagram showing where the O2 sensor is and said it was an easy change. Also said it could be left alone with little or no ill effects on the car because probably the only thing making the check engine light come on is that the exhaust is non-compliant with CA emission standards.

Still can't help thinking, since the car has 151K, that the 02 sensors probably need changing just from normal wear.

I'm in the process of seeing what kind of gas mileage the car gets. Does anyone know what kind of gas mileage these cars got when new?

[sx moneypit]

If it is an auto it is rated about 26 highway,21 in town.Mine gets about 18 to 20 in town.Mine is a 5 speed.

[sparkplugs.com]

Hey dzzydmb, at 154K it's not a bad idea to replace the sensors. Especially as they are fairly cheap:http://www.sparkplugs.com/results_app.asp

And lucky you, we're running a special on all O2 sensors right now for nicoclub! Just type in O2NICO at checkout for 10% off your sensor order

[Cone Junky]

Got the code reader and it said it was the oxygen sensor. Guy said it had to do with the exhaust temperature. Oh and it turns out the car has California emissions.

Guy gave me a diagram showing where the O2 sensor is and said it was an easy change. Also said it could be left alone with little or no ill effects on the car because probably the only thing making the check engine light come on is that the exhaust is non-compliant with CA emission standards.

Still can't help thinking, since the car has 151K, that the 02 sensors probably need changing just from normal wear.

I'm in the process of seeing what kind of gas mileage the car gets. Does anyone know what kind of gas mileage these cars got when new?

What is the code #? Who is "the guy" that is telling you what it is or isn't?What the hell is he talking about CA emmisions or exhaust tempature? There is a code for exh temp sensor/egr, but has nothing to do with the O2 sensor. The O2 is mounted on the exhaust manifold, so a "non compliant" cat back exhaust has nothing to do with it. An O2 sensor is one of the most critical parts of the fuel injection system. All adjustments and fuel trims are adjusted via the feedback of the O2 sensor, so there can be plenty of "ill-effects".

If it really is an O2 sensor code, just replace it, no need for any more questions.

[dzzydmb]

The guy is a mechanic I have used before. He got the code and looked it up in the shop and said it was the exhaust temp sensor/EGR. He also said there were a variety of things that could cause the reading and the O2 sensor being worn is a possibility. He printed a diagram of the engine showing exactly where the sensor is.

Cone Junky the guy also said even though the code technically has nothing to do with the O2 sensor, the sensor needs changing considering the mileage on the car.

I checked the sparkplugs.com price for the 02 sensors and it is indeed good compared with the price at the auto parts house. Only thing is, there's only one sensor shown to fit the car...does it use two of the same one? Or, is there just the one sensor on this car?

Also from the code reader he found that this car was sold new in California to CA specs for emissions. From reading on this site I know that means its computer is programmed differently in CA cars.

Thanks again for the assistance!

[Wc240]

pre 96 cars are obd1, obd1 systems use one o2 sensor, before the cat. its the feedback for your fuel control(as previously stated)

CA and federal(49 state) emissions are different. on 240s the main difference is the inclusion of a exhaust temp sensor. this has NOTHING to do with the o2 sensor. look it up in the fsm. the sensor is mounted next to the egr valve. its SOLE PURPOSE is to sense the flow of exhoust from the egr valve. throwing that code is one of two things. 1(less likely) the sensor or the circuit to that sensor is bad. or 2(most likely) the rubber hose connecting the BPT and EGR valves has burned a hole and is not alowing the egr to function. very common problem. its a .49 cent hose. replace it, clear the code, drive down the freeway for a while and see if the light comes back on. the egr valve only operates during cruise.

your "mechanic" is steering you wrong. the ex-temp sensor and the o2 sensor have NOTHING to do with eachother. if you have any other questions regarding this, i suggest looking for a different resource.

lemme know if you need any more info

oh yeah, it wouldnt be a bad idea to replace the o2 as preventative maintanence. but know this, the wire goin to my o2 sensor melted and seperated(i.e. no conection) i unknowinly drove like that for 3 months and never got a check engine light

[snowyred180]

Post some pics of the car. Sounds like you got a good deal. In the future, serach. There are many threads about the topic in question.

[Cone Junky]

OK. Your post made it sound like he was saying they were related.

Either your EGR is not working and the sensor is noticing or the sensor is bad. If you just want the light to go away, search for EGR delete on here. There should be a listing for the size resistor you can use to bypass the exh temp sensor. I have no EGR in a CA car and the resistor has worked to keep the light off.