# Service Engine Soon light :(



## TheCROW163 (Mar 1, 2007)

Hey guys, I was driving my 98SE Auto uphill a bit fast and I made a sharp right turn, all was well and I reached my destination soon after that.
A couple of hours later I turned on my engine and then the Service Engine Soon lighted up on my dash.
I tightened the gas cap, restarted the engine but the light stayed on.
Can anyone tell me how to find out what's wrong with it without having to hook it up to a scanner?
What can I do? The truck still drives normally.Thankyou all.


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## smj999smj (Jan 1, 2006)

Well, if the gas cap was loose and caused the code to be set, it will take several drive cycles before the light will go out. The ECM needs to see specific conditions before it will run the evap system self test. Your best bet is to check with your local auto parts stores and see if they will retrieve the stored code and clear the memory for you. Many will do this for no charge for vehicles with OBD II diagnostics, like yours. You could also pick up a code reader for less than $100 that will do the same thing. Or, you'll have to sit and wait until it goes out or pay $$ and have a repair shop look at it. Your choice!


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## TheCROW163 (Mar 1, 2007)

smj999smj said:


> Well, if the gas cap was loose and caused the code to be set, it will take several drive cycles before the light will go out. The ECM needs to see specific conditions before it will run the evap system self test. Your best bet is to check with your local auto parts stores and see if they will retrieve the stored code and clear the memory for you. Many will do this for no charge for vehicles with OBD II diagnostics, like yours. You could also pick up a code reader for less than $100 that will do the same thing. Or, you'll have to sit and wait until it goes out or pay $$ and have a repair shop look at it. Your choice!


Thanks for the reply;
The gas cap was already tight, but I unscrewed it and retightened it just in case.
I'll pass by the dealership tomorrow and have the code read.
I'll ask them to clear it and wait to see if it lights up again. where can I get the meaning of the codes?
Will post back tomorrow.


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## TheCROW163 (Mar 1, 2007)

TheCROW163 said:


> Thanks for the reply;
> The gas cap was already tight, but I unscrewed it and retightened it just in case.
> I'll pass by the dealership tomorrow and have the code read.
> I'll ask them to clear it and wait to see if it lights up again. where can I get the meaning of the codes?
> Will post back tomorrow.


Hi Guys, just got back from the dealership.
I pulled the codes and I took a pic of the print out.
What's your diagnosis?


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## golfer (Aug 21, 2006)

Well it looks like P0141 = rear heated O2 sensor right bank needs to be checked.


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## lewisnc100 (Apr 25, 2003)

There's some links on this site to the factory service manual that you can download for free, it will walk you through the diagnostic steps for that code.

Also in the future you can use the diagnostic mode selector screw on the ECU to flash the codes on your dash, no OBDII code reader needed for your Pathfinder.


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## TheCROW163 (Mar 1, 2007)

So does this mean that only one sensor needs to be replaced? cos I'm seeing 4 different code numbers.
Thanks a lot guys. PLease reply soon as I'm taking it tomorrow morning back to the dealership.


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## 2001pathy_SE (Apr 9, 2006)

TheCROW163 said:


> So does this mean that only one sensor needs to be replaced? cos I'm seeing 4 different code numbers.
> Thanks a lot guys. PLease reply soon as I'm taking it tomorrow morning back to the dealership.



try resetting the codes and see which ones come back. then you can fix the problems to all the codes that return.


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## TheCROW163 (Mar 1, 2007)

They reset the codes for me, but the SES light came back immediately when I started the engine.
What does the number under TIME mean? The code P0141 has time = 2 while the rest are = 0.
Any info would be greately appreciated.
Thanks.


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## smj999smj (Jan 1, 2006)

There are three differant codes; the numbers to the right of the codes are "incident numbers." An incident code of "0" means that the problem that triggered the code is current; an incident code of "2" means that the problem that triggered that particular code happened two trip cycles ago. 

When looking at the O2 sensor codes, you see "HO2S1 HTR (B1) [PO135]" 

HO2=Heated Oxygen Sensor
HTR= Heater circuit
S1= Sensor 1, or "upstream oxygen sensor" (aka front O2 sensor)
(S2 would mean "downstream" or rear O2 sensor)
B1= Bank #1, or the cylinder bank of the engine that includes #1 cylinder. In your case, it refers to the right side or passenger side (US models).
(B2=Bank #2, or the cylinder bank of the engine that starts with #2 cylinder. In your case, the left cylinder bank).
PO135=Diagnostic trouble code #

What's interesting is that they are all heater circuit codes. Heated oxygen sensors have a built in heater element to warm up the oxygen sensor. The heater circuits are all fed power via the same 10 amp fuse in the fuse panel and each heater has it's own ground side circuit to the ECM. The ECM, using the cam position sensor as referance, grounds the circuits to switch the heaters "on" and "off." The heaters are turned "on" below at engine speeds below 3200RPM. The engineers design the system to promote more accurate readings from the sensors to get more precise fuel management.

It's not uncommon for an O2 sensor heater element to break and require replacement of the O2 sensor. The fact that you have three differant O2 sensors that triggered heater codes at almost the same time would lead me to believe that the issue is not the sensors. Your sensors that have triggered codes are as follows:

Both front and rear oxygen sensors on bank #1 (right side of vehicle).
The front oxygen sensor on bank #2 (left side of vehicle).

The first thing I would do is look at what they have in common: the 10 amp fuse. So, check the fuse and make sure it has power to and through it and make sure it's firmly in place.

Another check you can do is to see if that power is getting from the fuse to the sensors. Unplug all of the sensors. Turn key "on" with the engine not running, and you should have 12 volts to each of the sensors (on the front sensors, it will be at pin "3").

If you want to do a componant test of the sensors, you'll need a multimeter or ohmmeter. For the front sensors, unplug them and check the resistance of pins #1 & #3 (pin #2 is the one in the middle). It should read 2.3 to 4.3 Ohms at 77 degrees F. Check continuity between terminals 2 and 1, 3 and 2. Continuity should not exist. If NG, replace the front heated oxygen sensor.

If the componant tests are good and there is power to all of the sensors from the fuse, then the issue lies on the ground circuit between the sensors (pin #1 on the front sensors)and the ECM harness connector or a failed driver within the ECM itself. One would have to do resistance tests on the ground side circuit of the O2 heaters to the ECM harness connector to confirm. If you wish to try this yourself and get this far, e-mail me at [email protected] for more info. Good luck!


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## TheCROW163 (Mar 1, 2007)

Thanks a lot for your reply!!!
My Pathy is made in Japan. Does this change anything?
Which 10Amp fuse are you referring to? Where can i find it?
Thanks a lot.


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## smj999smj (Jan 1, 2006)

With the exception of the most current model of the Pathfinder (which I'm not sure about), all previous models of the Pathfinder were made in Japan. It's not an issue.

Appears to be fuse #25 in your fuse panel, lower part of the driver's side of the dash. Your owner's manual may provide you with some assistance. Fuses are generally labeled on the back of the fuse panel cover.


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## TheCROW163 (Mar 1, 2007)

smj999smj said:


> With the exception of the most current model of the Pathfinder (which I'm not sure about), all previous models of the Pathfinder were made in Japan. It's not an issue.
> 
> Appears to be fuse #25 in your fuse panel, lower part of the driver's side of the dash. Your owner's manual may provide you with some assistance. Fuses are generally labeled on the back of the fuse panel cover.


Went to the dealership again and asked them to check the fuses, they did and told me that a fuse was missing!!!! I think they were referring to the engine control fuse which is the one you pointed out.
They put in a fuse and reset the SES light and ran the scan again: All was well.
I cannot imagine how a fuse could be missing, could it have fallen? Does this usually happen? If it was removed before, the SES light would have lighted up long time ago!!!
Anyways I'm keeping my eye on it and so far so good, I'm hoping this was the reason for the light.

Thanks a lot for your relply smj999smj, you saved me lots of hassle


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## 1990gsp (Oct 1, 2008)

lewisnc100 said:


> There's some links on this site to the factory service manual that you can download for free, it will walk you through the diagnostic steps for that code.
> 
> Also in the future you can use the diagnostic mode selector screw on the ECU to flash the codes on your dash, no OBDII code reader needed for your Pathfinder.


How do you do this?

I washed off my engine earlier and had a problem starting it... now I am getting the service engine light. It is starting now.


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## TheCROW163 (Mar 1, 2007)

If you have a VQ35 check this: http://www.nissanforums.com/pathfinder/130911-troubleshooting-engine-checklight.html#post1167047

If you have a VG33E check this: http://www.nissanforums.com/truck-suv/57119-i-give-up-where-diagnostic-screw.html


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## 1990gsp (Oct 1, 2008)

Cool... Thanks.


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