# Sensor location and pic



## ace (Aug 8, 2002)

Can someone direct me to a site that shows you the location of the following sensors:
1) O2 sensor
2) Engine temp sensor (cylinder sensor) not the watercoolant sensor


it would help if there were pictures of it too.

Trying to DIY some replacement.

Also my car has a hard start problem and after reading 'extensively', my guess to the problem is the above 2 components.

Any expert advise is much appreciated.


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## luminus (Jul 10, 2002)

If the O2 sensor is going, it shouldn't have any problems starting, but you're fuel milage will drop. Its located on the exhaust header, you should see it on the front of the engine sticking out of the metal heat shield with three wires.

Not sure about the engine temp sensor.

Aaron


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## toolapcfan (Jul 10, 2002)

I'll take a look in my FSM when I get home and let you know what I find. If you can't find your 02 sensor I'll take a pic of the one in my XE and post it for you. You'll need to borrow/purchase a special socket to remove the sensor. You might be able to get by without it if you remove the exhaust header heat shield and use a wrench but it's not easy to do it that way. I took one out of a '91 Tempo my wife had, that way. It was not easy.


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## toolapcfan (Jul 10, 2002)

Well from what I can find in the FSM the Thermal Transmittor, which appears to be what you're asking about, appears to be a single wire connector underneath the throttle body. 

EDIT: Okay, well I went out and looked at my car, and there is a single wire connector that hooks up to a sensor that is just underneath the coil and this sensor is in the lower portion of the head, so it's right above the block. This would make sense then, that it would be the cylinder temp sensor you're looking for. I'd take a picture but: 1) I don't have a digital camera at the moment 2) I don't think I could get a good picture of it in the first place. It's right under the coil, you can't miss it, it's the only thing there.


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## luminus (Jul 10, 2002)

I don't think either of these going bad should make your car hard to start, however.


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## ace (Aug 8, 2002)

hi, 

to toolapcfan: thanx. I looked and I found one connector with 2 wires under the coil. You can see it thru the distributor. It appears to be installed into the engine block. Is this the one ?Now that seems odd as you mentioned that there is only 1 wire. How is it that mine has 2 ?

to luminus:I tried to find the O2 sensor, but didn't see any component or wires sticking out from the exhaust header. Would I be able to see it under the front middle of the car? Near thr grille

This hard start problem really has puzzled many a mechanic. Replaced the AAC valve, distributor, battery and starter motor. Had installed new fuel pumps and filter too. Including new plugs, cable and air filter. What else other than coil, power transistor, temp sensor and O2.

My mileage also seems to vary between 8km/litre to 10km/litre (sorry I dun use mpg calculation). With all other driving and road conditions being equal.

Is this a challenge to the experts or what ?
The local dealer will charge me an arm and leg for the repairs.
So better to DIY.


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## toolapcfan (Jul 10, 2002)

I suppose it could have been two wires, but it's a single terminal connector that connects to a single spade terminal sticking out of the head. It's clearly a sensor and not a ground clip. If the O2 sensor were a snake you'd be dead, I'll guarantee it.  Open your hood and look at your exhaust header, there is a thing right in the middle of it, it has a black wire that runs to a little red cone shaped plastic connector that hooks up to a thick black cable. This thing sticking out of your header is the 02 sensor. It's right on the top of the header, near where it connects to the head.


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## ScarCrow28 (May 14, 2002)

i just replaced my O2 sensor. i believe that GA's only have one wire running from them. i replaced it with a bosch one. the wire was longer, wich isn't nessarily a bad thing. the holder on my heat shield rusted off so now i just tied it somewhere else.

But, i had replaced it to solve my LOW FUEL MILEAGE problem. i've been getting around 26-31mpg. really really low for a car rated at 38!!!. so far i've only put in one tank and my mileage looks to end up at 27-28. not any better at all. i wonder if my Advanced timing and 93 octane has anything to do with the mileage problem. i advanced and upgraded the fuel about a week or so b4 putting in the sensor. i still would think i'd gain at least 2mpg, but so far, didly squat! the car feels tourqier, but i credit that to the timming.

as a hint to change the o2: my uncle had to modify an old wrench to fit into the gap in the header, shaving the outside of the wrench, and cutting the handle in half. the size for the GA is 22mm. and it helps to try to REMOVE WHEN THE ENGINE IS WARM. just grab an old pot holder, your wrench, a small hammer, and a screwdriver. put the wrench in place, use the screwdriver to hold it in place, so you don't have to touch it, it will get hot very fast. then hit the wrench with the hammer. after a few taps the sensor should come out with no problems.!!! after a few taps you can take the pot holder and just unscrew the sensor the rest of the way. oh yea be sure to unplug the wire first, jsut move the boot out of the way and wiggle the wire away, don't worry about breaking the boot, the new sensor has one with it. PLUS it include some anti seize on the threads, DO NO REMOVE, or else you will have an even harder time to remove next time, like if your buying a header or whatever.

remember HEAT HELPS!!!

i'd post a pic but the rules say that i can't post attachments, and i have no idea how to do it any other way i could AIM it to ya, but we'd have to be connected


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## PatScottAKA99XE (Apr 30, 2002)

Ill try to help here.
On my B14 with a GA, which is probly the same as your car. There are 2 temp sensors. One is for the gauge and it is a one-wire sensor. The other is for the ECU, this is the one I assume you need to locate. On My GA the one under the distributer is a one-wire, thats the one that runs the gauge(I have confirmed this). the 2 wire one is on the intake manifold side(rear) of the engine. If you look behind the oil fill cap down twords the intake manifold thats where it is, dont quote my on this, but i belive the wire colors are brown/yellow and black(this is on a B14 yours may be different.) A B13 MPFI GA should be set up the same as a B14 MPFI GA. Ill take a look around my car tommorow(pics too)

BTW they are both water temp sensors

The O2 sensor(s) will be the only thing screwed into your exhaust with wires coming out of it. If you need help with testing these thing give me a holla. One more thing.. If you are having trouble with your car starting its probly not the O2 sensor. The ECU doesnt give a $hit what the O2 sensor says at start-up.
As for the temp sensor causing it.. again probly not, but it would make your ecu either dump too much or too little fuel at start-up.
If you are still suspecting these though, like I said give me a holla and I will help you with how to test them.
Why excatly is your car a hard start.. does it crank but not start of does it not crank at all some times?


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## ScarCrow28 (May 14, 2002)

PatScottAKA99XE said:


> *Ill try to help here.
> On my B14 with a GA, which is probly the same as your car. *


his profile says its a B13. i know my B13 has only one o2 sensor, in the header. i even got the Haynes manual to back me up on that one, it mentions only one sensor in the header. i hear others speak of two in B14s

sorry i read your post two fast, i've edited it like 4 times already


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## PatScottAKA99XE (Apr 30, 2002)

Yeah, one o2 and two water temp..like my post says


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## ace (Aug 8, 2002)

Hi guys

third time I'm posting .. some problems with the BB that keeps saying I'm an unregistered guest even after logging on.

Thanx to all for the valuable advice.

I found the temp sensor that I think goes to the gauge. It's a single wire. I cleaned the contacts but my problem still persisted.

Will look next for the other engine temp sensor.

Still have yet to find the O2 sensor. Do I have to remove the engine guard (plastic cover) under the front to see the O2 ?

My hard start problem begins like this:
In the morning, it takes about 3-4 cranks to get the engine to run.
Or I could crank at one go for ~5secs to get the engine to run.

Once it runs, no peoblem.
When I stop the engine and crank it within 10 mins, it'll be normal and ok.
Have to leave the engine to cool down totally in order to replicate the problem. SOmetimes 30 mins, sometime 6 hrs.

It doesn't help that I dun have a diagnostic computer nor the technica l manual. And mechanic costs here are really expensive.

I've actually narrowed down the problem to a few components:
coil, power transistor and engine temp sensor.

Does anyone know the part number or OEM parts that can be used?

Hope I can solve it soon.


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## ScarCrow28 (May 14, 2002)

i was getting the same problems loggin in. in fact still have trouble with it from time to time. at one point it got so bad that i couldn't go anywhere at all. i hit any link after logging in, and i'm suddenly logged out. even trying to get to my user profile would log me out again! i had to turn off the use of cookies and now i need to log in everytime i visit the site.

i'm still puzzeled that you can't find the o2 sensor. pop up your hood, then look down at the engine. on the front of the engine, which should be in plan sight, is the header. unless you had someone install a new aftermarket header, there should be sticking up, a goldish colored thingy plugged into the header. with a single wire leading out the top of it. see if you can find it in this pic:









if your engine doesn't look anything like that, well i'm stumped. this image is out of an NX from the first NPM issue, but the engine is the same.


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## PatScottAKA99XE (Apr 30, 2002)

ace,
Here is a pic of the ECU's water temp sensor on a GA:










For reference, you can see just a bit of the oil cap in the lower right hand portion of the pic.


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## ace (Aug 8, 2002)

Hi, thanx guys for the pix.

that really helped alot. Now I know why I couldn't find the O2 sensor, coz there's this metal plate (shield or guard) that covers that portion. In addition I've been trying to look at the sensor from under the car.. from my experience with continental cars.

As for the engine temp sensor, I did a quick check and found it too. Lot's of grime and soot. And the connector's a little bit broken. Guess the heat in the engine compartment may have caused the plastic to breakdown.

Can anyone tell me the part number of the items so that I can get it at the local auto shop ? Can any O2 sensor or temp sensor do ?

I've decided to get an after market coil. May have to do some modification to the wiring and connector.
I've replaced the plug cable from coil to distributor, but still the problem persists.

Got to remove the engine cover and sheesh.. looks like the engines got lung cancer or something...all the gunk and thick goo. Can this result in hard starts ? Any meands to flush all of that gunk out without having to put new engine seals or grind the cylinder heads ?
My local mechanic advises against pouring additives or flushing the engine. An 11 yr old car might give off white smoke after that. According to him.


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## toolapcfan (Jul 10, 2002)

Ace, I thought you wanted the cylinder temp sensor? That's the one under your coil. The one Pat took a picture of is the water temp sensor. 



> _Originally posted by ScarCrow:_
> *"...see if you can find it in this pic:"*












I found it! What did I win?


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## PatScottAKA99XE (Apr 30, 2002)

toolapcfan said:


> *Ace, I thought you wanted the cylinder temp sensor? That's the one under your coil. The one Pat took a picture of is the water temp sensor.*


* 
For clearification:
They are both water temp sensors.

The one under the dist. is only for the dash temp qauge.

The one in my pic is where the ECU gets its temp readings from.

The one under the dist. has absolutley no affect on how the engine runs.

The one in my pic has an affect on how the engine runs.*


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## ace (Aug 8, 2002)

Hi,

yep. I need to know the sensor where the ECU will take readings from.

My hard start problem seems to be getting worse.

Takes more cranks and a longer time to get the engine running.

Do any of you guys think that by resetting the ECU will help ? Or does the ECU actually reset each time you crank the car.

I've read somewhere that the ECU updates the last 50 cranks for diagnostics. Not sure if the ECU gets 'affected' by the history of problems.


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## PatScottAKA99XE (Apr 30, 2002)

Then you need the one in my pic.
History problems will not affect the running of your engine. It stores them for guys like me(technicians), so that we can see if it has been a recurring problem. Resetting probably wont work.
I know GM's reset(clear history problems) after about 40 key cycles. If and only if the problem doesnt happen again during that 40. I dont know what Nissan cycle number is.

I cant do metric conversion either, but is your gas mileage(Km'ige?) worse than normal?
Have you noticed any other drivability problems? Even little things
Does this hard start happen all of the time?
just trying to get some info.


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## ace (Aug 8, 2002)

Had the chance to look into the bonnet yesterday and guess what I found ? Nothing.... the O2 sensor wasn't even close to where the picture was. None on the header, none under the header.. very puzzling !! No wires were seen coming out from anywhere near or in the exhaust header. Did I miss something? 
I didn't see any longish sensor that we recognise as an O2 sensor.
Is the sensor only used in manual cars ? Mine's automatic.
A challenge to you experts out there ?

Yes the hard start happens all the time. Previously I could start the engine without problems within an hour after shutting the engine. But it seems like even 30mins after shutting down, I need at least 3-4 cranks to get the engine to kick in.

I sprayed the contacts of the power transistor and coil with contact cleaner and that seemed to work. But only briefly. What I can describe is that there is a difference in the cranking sound produced for a hard start versus a good one time start. A good crank produces a low frequency crank and vroom sound. Whereas a hard start produces a weaker cranking sound as if the battery had no juice.

Also, is there a fuel pressure regulator / valve or sensor that determines the fuel pressure around the fuel lines ? I thought the fuel line only consists of the fuel pump and filter. Any components around here ?

My gas mileage goes between 8-10 km per litre. Same conditions in driving.


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## toolapcfan (Jul 10, 2002)

Ace, go back to that pic where I posted the arrow pointing to the 02 sensor, does your exhaust manifold have a cover like that one does, with a depression where that 02 sensor is? If so, then you should have an 02 sensor there, if not, then, heh, you have no 02 sensor for some reason, and you NEED one. There should be a nice gaping hole into the header right there where the 02 sensor is supposed to be. If your header doesn't look like that one, then I don't know what to tell you. If your car has an aftermarket header, the 02 sensor would still be on it, somewhere further down where the pipes join.


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## ace (Aug 8, 2002)

Yes.. my car is similar to the pix that u sent.

Except that the dipstick area where the depression is, there is no O2 sensor. It's completely flushed. No hole, no wires.

I believe the O2 must be around somewhere. I've looked under, over , around. You name it.

Can the car function without an O2 ?
Maybe the previous owner forgot to install it back ? I had my gearbox replaced, could they have forgotten ?


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## toolapcfan (Jul 10, 2002)

You're kidding right? There's no depression in the exhaust manifold heat shield? Or there is but there's no hole there? Wierd, I have no clue why that would be. Somebody has got to know what the deal with that is, unfortunately, it isn't I.


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## ace (Aug 8, 2002)

yes, amazing as it sounds... no hole.

looks like an original exhaust cover to me.

There's a depression, but no hole.
Holey moley...

Any experts out there who can give me a clue as to where my O2 sensor is ?

I've looked down from exhaust header to the end of the tail pipe. Don't see any sensor that resembles an O2.

COuld it be relocated somewhere on the engine block ?

Must the car run with an O2 ?

Or should I just ask the mechanic to replace the O2 and let him cry in vain and possible bill me a hefty bill ?


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## ScarCrow28 (May 14, 2002)

well you could try to go to the library and locate a haynes style manual for you car. its pretty much a technical book that tells you how to take apart and put back everything on the car. you might even be able to go to your local parts store and find a book to take a peek at. over here sometimes one or two are unwrapped. 


it might be possible you car was never required to pass any emmisions tests or whatever, so it was cheaper for the company just to omit it. as far as i know, the car can run without one. all it does is monitor the fuel mixture when the engine is warm and calibrate it for maxuim fuel and emmisions efficency. thats the next best guess i can give ya.

usually all engines, auto or manual have this sensor. they do differ in size depending on the car. 

have you tried looking further down the exhaust? near the cat somwhere?


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## toolapcfan (Jul 10, 2002)

I don't know what year your car is, but I have a Haynes that cover your car and I can almost guarantee that there won't be anything about it in there. I also have a '93 FSM and if it's not in there, then I'd have to say that you're going to have to go to Nissan to find out. I think SCarcrow might be on to it, that since you're in Europe (I'm assuming) that they didn't need the O2 sensor to pass emissions, so they simply didn't put one in. I doubt it's the reason for your hard starts anyways. I'd just ask Nissan about it. If you have one at all it will be on your exhaust somewhere. It has to measure exhuast gas to work.


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## ace (Aug 8, 2002)

somehow I have to re-post a few times. Do any of you guys encounter this problem ?

My car was registered (possibly built) in 1991; and where I am (singapore) we do have strict emission standards for all vehicles.
Cars older than 10 yrs have to pass this check every year. Mine is due soon.

I had a look under the car again yesterday and looked from header to the cat converter to the tail pipe and found nothing. 

As mentioned by toolapcfan, the sensor could be in a different shape or size. Of which I didn't find any along the exhaust lines.

I just may have to call on my Nissan dealer to get some clues.

I'm thinking to replace my coil with an aftermarket sports one. Just have to do some wiring changes. Any thoughts to that ?


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## ace (Aug 8, 2002)

Hi guys,

been examining my car for the last few days and this was what I found:
Resistance of my water temp gauge seems to be ok. Reduces when engine heats up. More importantly is that it was reading the correct ambient water temp in the engine.
Resistance of the coil also looks ok. Ditto to the plug wires; but I'm gonna change the coil anyway.
Power transistor looks ok, sprayed all contacts with contact cleaner and managed to get lot's of grime off most of the sensors.
Got to clean my throttle body chamber too as well as the butterfly valve. That didn't improve my consumption tho.

I think I found my O2 sensor ! It appears to be mounted behind the first chamber of the ECCS housing (near the engine temp sensor). It's a 2 wire sensor with a cylindrical body. If this is the one, then access to it will be a nightmare. Besides, I was unable to get parts for this. Will any OEM O2 do the job or do I have to get back the original ?

But the car still has a hard start problem !!

Been reading around the web and there was a suggestion to check the fuel pressure regulator. Since after shutting the engine off, it would have to preserve some fuel to the injectors. So before I proceed to check, can anyone tell me where this regulator is? I saw one that looks like a top hat (from Abe Lincoln) that has a thin rubber hose from the fuel filter; and the other hose joins to the ECCS. It's located near the injectors. Is it better to get an aftermarket one (with variable adjustment) or the original piece?

Any help on this ?


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## Guest (Sep 5, 2002)

THAT TEMP SWICH BY THE OIL FILLER CAP ON THE MAIFOLD IS THE FAN SWICH TO TEST UNPLUG IT AND YOUR FANS WILL COME ON . IT SENCES THE TEMP OF THE WATER IF TO HOT THE FANS COME ON. HOPE THIS HELPS


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## PatScottAKA99XE (Apr 30, 2002)

BAM!! you just hit on a good possible cause, I cant belive I missed it. In the fuel pump(most) there is a "check ball". This ball is what keeps the psi in the lines(nothing to do with the regulator). I have seen many a vehicle come in with a dirty fuel problem, and after cleaning the system it still has a hard start problem. If I were you, I would get a hold of a fuel psi gauge and hook it up. Start the car, shut it off and then see if it holds pressure.
I am pretty sure Nissans are set up like this with the check ball in the pump/housing. It is possible that one could be in the regulator area though. The "top hat" with a vacum line going into it, and that is on the injector rail would be the fuel psi regulator.

I would steer away from the O2 sensor and do the test I mentioned. Having a faulty check ball would certainly cause the hard start after sitting, but not why still warm due to the fact the the psi hasnt had time to "bleed" down.


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## ace (Aug 8, 2002)

Hi PatScottAKA99XE,

I've just changed the pump and filter about 6 mths ago. The mech did say the fuel was dirty. But this problem of hard start did occur long before I replaced the previous pump.

Is the check ball located in the pump as well or is it outside, around the pump area ?

Which place would I be able to hook the fuel gauge and monitor it. Before or after the fuel filter ?

As I might not be able to get hold of a fuel gauge, my next calculated risk move is to replace the fuel psi regulator and the fuel hoses. Reason being that the car can start immediately (in a blue moon) on some occasions and that has led me to think that if it's not electrical, then it has to be the fuel portion.

This might also solve my hesitation (loss of power) problem that I posted in this BB too. However, the regulator is a rather expensive part and I hope the risk is worth it.

As someone said, the hard start has 30 + components that may cause it. Unfortunately I don't have the time and luxury of completely troubleshooting the problem hence I can only perform educated guesses and rely on the generosity of experts in this BB. Thanx again.

Will keep you guys posted of my progress and success.


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## ace (Aug 8, 2002)

Got to buy the fuel pressure regulator. An expensive component for such a size.

Removal of the old regulator could have been simpler if not for the 2 screws holding the regulator. Also try not to remove it when the engine is hot. The screws won't budge at all.

Anyhow, when it was all removed, installation was a breeze. The fuel tube and vaccuum tube were also replaced. Some problems were occurred during the vaccuum tube installation, but as long as the tubing covers 1/4 of the piping, should not be a problem.

After installation, I cranked the engine and behold , it started first crank ! The sound of the engine also was much deeper.

The next morning I managed to crank it first time too. But my joy was short lived as the later part of the day cranking was about twice. So I suspect there may be more to it than just the fuel regulator.

Worse of all a few hrs ago, my car wouldn't start at all. There was good crank, but it seemed that no fuel was delivered. I suspected the pump at first, but when I stepped on the pedal to crank, it managed to start.

Could it be vapour lock ? Anyway to overcome this problem ?


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## j-pizzle (Apr 15, 2007)

crank position sensor


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