# check engine is on



## Fred_Tao (Jun 25, 2004)

the check engine came on lately sometime on my 94 Altima GLE, and went off usually after a couple of minutes. I did not feel any difference about the engine. This has happened 4 times since I bought the car, a month ago. I went to the shop, they said you had to come when the light was on, but it is off in most time. Is there anybody who has an idea, whether it is a big problem or just defective electrical cable/connector? 
thanks


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## Ruben (Oct 15, 2002)

Check your gas cap.


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## Fred_Tao (Jun 25, 2004)

*I just checked the fuel filler cap*



Ruben said:


> Check your gas cap.


I just checked the fuel filler cap, which seems to be ok. but I remember that sometime when I turned the fuel cap, there was some sound " hissing", (fuel was under pressure) but this time I didn't hear anyting and the cap might be loose ( I am really not sure because it was just easy to turn) . Is that a problem?


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## mzanubis (Feb 19, 2003)

Fred_Tao said:


> I just checked the fuel filler cap, which seems to be ok. but I remember that sometime when I turned the fuel cap, there was some sound " hissing", (fuel was under pressure) but this time I didn't hear anyting and the cap might be loose ( I am really not sure because it was just easy to turn) . Is that a problem?


turn it till it clicks buddy, lol
anyway, just take it down to a machanic, or for that matter, the damn AutoZone and have them hook it up to their computer, i think its either free or really facking cheep.


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## Fred_Tao (Jun 25, 2004)

mzanubis said:


> turn it till it clicks buddy, lol
> anyway, just take it down to a machanic, or for that matter, the damn AutoZone and have them hook it up to their computer, i think its either free or really facking cheep.


oh,my god! you think I didn't turn it till it clicks?


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## Fred_Tao (Jun 25, 2004)

Fred_Tao said:


> oh,my god! you think I didn't turn it till it clicks?


I called Nissan Dealer today, and they said that I should bring my car there only when the light stays on because the ECU doesn't store code when light's gone off. 

Just ask if I can check the ECU code by myself and how?


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## skylineawd (Dec 3, 2002)

You can check the ECM by yourself and IT WILL HAVE THE CODE STORED.

Pull back the plastic piece down by your accelerator pedal. The ECM is right there. Then turn the ignition key to On, do not start.
You'll see a screw next to the LED light, which should be on. Turn the screw clockwise untill it stops, let it sit there for a few seconds, then turn the screw back, and you should get a series of long and short blinks from the LED, count how many long and then count how many short, then look them up in the haynes manual and it will tell you what code it is storing, if you don't have one post it on here and I'll look it up. They you need to turn the screws clockwise again, and hold for a few seconds and then turn the screw back to normal, this will erase and stored engine codes in the ECM.


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## Fred_Tao (Jun 25, 2004)

*thanks*



skylineawd said:


> You can check the ECM by yourself and IT WILL HAVE THE CODE STORED.
> 
> Pull back the plastic piece down by your accelerator pedal. The ECM is right there. Then turn the ignition key to On, do not start.
> You'll see a screw next to the LED light, which should be on. Turn the screw clockwise untill it stops, let it sit there for a few seconds, then turn the screw back, and you should get a series of long and short blinks from the LED, count how many long and then count how many short, then look them up in the haynes manual and it will tell you what code it is storing, if you don't have one post it on here and I'll look it up. They you need to turn the screws clockwise again, and hold for a few seconds and then turn the screw back to normal, this will erase and stored engine codes in the ECM.


thanks, it is really easy to do it. I got two codes: 32 and 34. what is that supposed to mean?


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## asleepz (Feb 24, 2004)

well the haynes manual has descriptions of every code next to it. Some codes I think you are supposed to have just check in it. It is the all knowing paper of knowledge


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## Cilver (Jun 22, 2004)

Fred_Tao said:


> thanks, it is really easy to do it. I got two codes: 32 and 34. what is that supposed to mean?


I have a Chilton manual handy...

*Code 32 (EGR Function)* - _Detected when EGR valve does not operate (valve spring doesn't lift). Check EGR valve / EGR and canister control solenoid valve._

*Code 34 (Knock Sensor Circuit)* - _Detected when the knock sensor circuit is open or shorted (an abnormally high or low voltage is entered). Check harness and connector / knock sensor._


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## asleepz (Feb 24, 2004)

sometimes is says that ECM's will put out codes that are normal. Are those two on that list?


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## skylineawd (Dec 3, 2002)

SKD_Tech said:


> sometimes is says that ECM's will put out codes that are normal. Are those two on that list?




Code 34 Knock Sensor is one of the most common thrown codes by the ECM. Most of the time it is thrown as a precautionary code, letting you know that something is wrong. I would check your EGR valve first, then check your codes again.


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## Fred_Tao (Jun 25, 2004)

*Thanks*



skylineawd said:


> Code 34 Knock Sensor is one of the most common thrown codes by the ECM. Most of the time it is thrown as a precautionary code, letting you know that something is wrong. I would check your EGR valve first, then check your codes again.



Thanks, I just checked the EGR system and found out that there was a balck hose to the charcoal canister disconnected. I had my car fuel filter changed last week, the hose is very close to the fuel filter, I think the mechanic must have pulled it off to ease the work but forgot to connect it back.
I have clear the ECM memory and hope the light wouldn't come back.
thanks for the help.


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## skylineawd (Dec 3, 2002)

Let us know if it comes back up. I would check the ECM again in about a week.


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## Fred_Tao (Jun 25, 2004)

skylineawd said:


> Let us know if it comes back up. I would check the ECM again in about a week.



for a couple of days already, the check engine light hasn't come back again, and I think it wouldn't come back.

the problem is that after I connected the black hose back to the top of the charcoal canister, my car's driveability decreased down to level before I changed the fuel filter. I changed fuel filter because I wanted to inprove the driveability.

Right now, the car is a little hard to accelerate, and stumbles in low speed. when I press the pedal in high speed, it is not easy to increase the RPM. Also the car is louder than before. I can hear the noisy sharp sound clearly when engine is running. 

The car ran wonderfully in the period when the hose was not connected to the charcoal canister, except that the check engine light annoyed me. I just don't understand.

Is there any ideas? Do I need to change a charcoal canister? Thanks.


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## skylineawd (Dec 3, 2002)

That cannister connects with your BPT valve or back pressure, I would check for any vaccum leaks in your hoses, or cracks, or tears.


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## Fred_Tao (Jun 25, 2004)

skylineawd said:


> That cannister connects with your BPT valve or back pressure, I would check for any vaccum leaks in your hoses, or cracks, or tears.



I just checked ECM again today. As I cleared the code last week, and check engine light hasn't come on since then, there should be 55(normal). But I got a code: 34. Can I conclude that the bad driveability problem is caused by the knock Sensor?


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## Ruben (Oct 15, 2002)

It sure could. A bad knock sensor will retard the timing, giving you sluggish performance and poor gas mileage.


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## Fred_Tao (Jun 25, 2004)

Ruben said:


> It sure could. A bad knock sensor will retard the timing, giving you sluggish performance and poor gas mileage.


It does make sense. but why did the car run perfectly when the hose to the charcoal canister was disconnected?


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## skylineawd (Dec 3, 2002)

Ruben said:


> It sure could. A bad knock sensor will retard the timing, giving you sluggish performance and poor gas mileage.


WRONG!!!

A bad knock sensor WILL NOT retard timing on our cars. The knock sensor code is thrown as a precautionary code for another reason, however most times you will not notice another code coming back up. I would say it is not a bad knock sensor because the ECM was cleared, and then showed it later on, a bad knock sensor will trigger the ECM at all times if the voltage is out of range.

Most knock sensors do retard timing when they detect knock, but the nissan knock sensor was designed with the ECM to not fluctuate timing.


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## Fred_Tao (Jun 25, 2004)

skylineawd said:


> WRONG!!!
> 
> A bad knock sensor WILL NOT retard timing on our cars. The knock sensor code is thrown as a precautionary code for another reason, however most times you will not notice another code coming back up. I would say it is not a bad knock sensor because the ECM was cleared, and then showed it later on, a bad knock sensor will trigger the ECM at all times if the voltage is out of range.
> 
> Most knock sensors do retard timing when they detect knock, but the nissan knock sensor was designed with the ECM to not fluctuate timing.



So, what is the problem?


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## Ruben (Oct 15, 2002)

skylineawd said:


> WRONG!!!
> 
> A bad knock sensor WILL NOT retard timing on our cars......
> 
> Most knock sensors do retard timing when they detect knock, but the nissan knock sensor was designed with the ECM to not fluctuate timing.


Errr....So if the sensor is BAD, couldn't it retard timing, just because its bad and not actually sensing knock?


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## skylineawd (Dec 3, 2002)

Nope, my knock sensor went out on mine and timing was not adjusted, I even disconnected it to send no voltage back and still nothing changed with the timing, but I did pull code 34 up. I did months and months of research after I got that code, even though it wasn't the knock sensor. I'll c what else I could think of.


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## Fred_Tao (Jun 25, 2004)

skylineawd said:


> Nope, my knock sensor went out on mine and timing was not adjusted, I even disconnected it to send no voltage back and still nothing changed with the timing, but I did pull code 34 up. I did months and months of research after I got that code, even though it wasn't the knock sensor. I'll c what else I could think of.



I just found out that the EGR valve diaphragm can't be moved up by hand. It looks like a whole thing with the "seat". Is it possible that the bad EGR calve causes the bad driveability problem?

In addition, how can I fix a rusty valve or install a new one? Thanks.


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## skylineawd (Dec 3, 2002)

Fred_Tao said:


> I just found out that the EGR valve diaphragm can't be moved up by hand. It looks like a whole thing with the "seat". Is it possible that the bad EGR calve causes the bad driveability problem?
> 
> In addition, how can I fix a rusty valve or install a new one? Thanks.


If your EGR valve is stuck that will definately cause driveability issues. I would check that first.


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## NateDogg (Aug 11, 2004)

My check engine light was on starting around 103,000 i think, but then a few months later it turned off. I think my friend unhooked the o2 sensor and it went off then and he plugged it back in and the light was no longer on. I went to Advance Auto to see if they could pull codes but they couldn't because the light wasn't on.


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