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2004 Nissan Sentra engine check light is on , af , Please help !!

6K views 15 replies 4 participants last post by  saint0421 
#1 ·
The engine light came on , on my 2004 Nissan Sentra and I took it to Autozone and the hooked it up for their handheld computer and it showed a
P1279 , which this what stated :

Definition :
AF sensor 1 slow response

Probalbe Causes :

1. Failed AF Sensor
2. open or short circuit conditon
3. Vaccuum Leak in engine
4. Fuel injector or pressure regulator fault

I bought a can of CRC mass air flow sensor cleaner , will that help ? Any advice what I can/need do . Please be specific because I am new in this , thanks Rose
 
#2 ·
It's not your air flow sensor. That code corresponds to your Air/Fuel sensor, aka first oxygen sensor. I believe you need a new first oxygen sensor.

If you have less than 80k miles, it should be covered under the emissions systems defect warranty, which is good to 80k miles/8 years as mandated by federal law. Either that or the powertrain warranty, which is good for 60k miles/5 years. Either way, Nissan should foot the bill as long as you're below the mileage.
 
#3 ·
redroses said:
The engine light came on , on my 2004 Nissan Sentra and I took it to Autozone and the hooked it up for their handheld computer and it showed a
P1279 , which this what stated :

Definition :
AF sensor 1 slow response

Probalbe Causes :

1. Failed AF Sensor
2. open or short circuit conditon
3. Vaccuum Leak in engine
4. Fuel injector or pressure regulator fault

I bought a can of CRC mass air flow sensor cleaner , will that help ? Any advice what I can/need do . Please be specific because I am new in this , thanks Rose
P1279 is an open heater circuit on the #1 O2 sensor; bad connection or wire, possible bad O2 sensor...................
 
#4 ·
My car has 79000 miles on it . How much will it cost for me to fix it , can I do it myself or have a mechanic do it . The guy at autozone lookup the mass air flow sensor which the part itself is 254 $ + tax . Will it help if I still clean with the Mass air flow sensor
thank you for ya'll fast response .
 
#5 ·
It's not the mass air flow sensor that's gone, it's the oxygen sensor, the first one in the exhaust pipe. You should be able to see it screwed into the exhaust manifold, in front of the engine, with wires coming out of it. The sensor itself would probably cost around $125-$150 from the dealership, but you can most likely pick one up from Autozone for cheaper.

But if you're only at 79xxx miles, you're still under the emissions warranty and this repair shouldn't cost you a dime. Go to your local dealer, tell them you have a bad first oxygen sensor, and that it should be covered under the 8yr/80k mile emissions warranty. Should be completely free. But if not...

I'm not exactly sure what's involved with replacing that sensor on that motor. I don't know if you have to remove the heat shield or whatever. But once you get to it, with the right size socket/wrench (if using a socket you need a special o2 sensor socket), it'll come out but it'll probably take quite a bit of force. Basically just unplug the sensor, unscrew it from the exhaust, screw the new one in, and plug it in. It's just getting to the sensor and breaking it loose that are the problems. If you're comfortable working on your car and have the right tools it's not difficult. If not, any mechanic or muffler shop should be able to swap it out for not too much money.
 
#7 ·
Basically the sensor that the engine uses to tune itself isn't working correctly, so at any given moment the engine may be running too rich or too lean. Is it going to cause damage? In the short-term, most likely not. You might just notice increased fuel consumption, though probably not that bad.

If you're planning on taking it into Nissan you should do so as soon as possible to slip yourself in under 80,000 miles. Even if not, you should still get it done as soon as possible to avoid any possible complications. It's a job that shouldn't take a competent mechanic more than a half hour, especially if you bring the part with you.
 
#8 ·
armadnigeneral said:
Basically the sensor that the engine uses to tune itself isn't working correctly, so at any given moment the engine may be running too rich or too lean. Is it going to cause damage? In the short-term, most likely not. You might just notice increased fuel consumption, though probably not that bad.

If you're planning on taking it into Nissan you should do so as soon as possible to slip yourself in under 80,000 miles. Even if not, you should still get it done as soon as possible to avoid any possible complications. It's a job that shouldn't take a competent mechanic more than a half hour, especially if you bring the part with you.
thank you , Rose
 
#9 ·
Before I’d spend five cents on replacement parts, I’d be checking the sensor heater circuit and its connections. Many of these types of heater circuit issues are traced to loose connection and/or burnt wire harness problems. If you do not check the circuit and fix any problems first, jumping for a new sensor will accomplish nothing as the new sensor’s heater won’t work either………..
 
#10 ·
JFP in PA said:
Before I’d spend five cents on replacement parts, I’d be checking the sensor heater circuit and its connections. Many of these types of heater circuit issues are traced to loose connection and/or burnt wire harness problems. If you do not check the circuit and fix any problems first, jumping for a new sensor will accomplish nothing as the new sensor’s heater won’t work either………..
How can I check that and where is it located
?
 
#11 ·
You need to be looking at the wiring harness that goes to the O2 sensor in question. It has several wires in it, and you need to see if the wire that carries current to the sensor heater is working/shorted/burnt/frayed, etc. To do this, you will need an electrical test meter (volt meter) and the wiring layout from an FSM, which you can download (run a search for it)............. Entire test process take about 5 min................
 
#12 ·
JFP in PA said:
You need to be looking at the wiring harness that goes to the O2 sensor in question. It has several wires in it, and you need to see if the wire that carries current to the sensor heater is working/shorted/burnt/frayed, etc. To do this, you will need an electrical test meter (volt meter) and the wiring layout from an FSM, which you can download (run a search for it)............. Entire test process take about 5 min................
What is the FMS and where can I don't load it . Sorry for all these questions and I appreciate your help .
 
#15 ·
I'm frustrated , I took my car to autozone tried to get the code cleared and they wouldn't do it because it's against OHSA regulation and I would have to take it to a mechanic . They assumed I wanted to clear it so I can pass the inspection [ uh my sticker won't expire until Nov. ] . So I ask the guy , well I bought a can of " CRC " AIR FLOW SENSOR CLEANER and if I can't get it cleared and see if it did some good , how I supposed to know . Well the guy just look at me and said " I don't know " . So I told him I would bring the can back and wanted a refund , which I paid over 7 $ for it . Any advise or feedback on this .
 
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