camshaft position sensor?

A forum for the legendary Nissan Pathfinder and Infiniti QX4.
pprasai
Posts: 13
Joined: Sat Jul 14, 2007 2:53 am
Car: 2001 nissan pathfinder se 3.5

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hey everyone

i have a question

what does the camshaft position sensor do.. its functions

what happens if one of the sensor fails to work?

any difference?



LiquidLunch
Posts: 6
Joined: Wed Jun 27, 2007 3:48 pm
Car: 02 Pathfinder

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It measures the position of the camshafts.

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Andrew224
Posts: 332
Joined: Sat Sep 01, 2007 7:10 am
Car: 2001 Infiniti QX4, 2006 Maserati GranSport, 2002 Harley Davidson VRod
Location: Plainfield, IL
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It monitors the position of the camshaft while the engine is running. I would imagine the vehicle's computer would need this information so that it would know when to inject fuel into the cylinders and when to ignite it. In doing this, it would ensure that the engine is operating with maximum power and efficiency.

I just had the camshaft position sensor replaced on my '01 QX4 (39K miles) about a month ago. If it goes bad it will trip the dash board check engine light. Your truck may have emissions problems, poor gas mileage, engine may run rough, or quit on you.

Thankfully, I had the repair done under an Infiniti extended warranty so I have no idea what it might cost out of pocket.

Andrew

mvmcali
Posts: 103
Joined: Tue Nov 20, 2007 12:00 pm
Car: 2001 Infiniti QX4

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I just replaced these 2 camshaft sensors. $300 bucks!I was told they dont affect performance at all. which makes me wonder why have them!milage is 70k 2001 qx4

did anyone pay much different than I did?

KALMUSI
Posts: 8
Joined: Sun Oct 28, 2007 7:23 pm
Car: 2001 Nissan Pathfinder 4WD 5sp

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I replaced the two Intake VTC Sensors - not to be confused with the one Camshaft Position sensor on my 2001 Pathfinder with 129K miles recently. Only one was throwing a DTC code P1140, but I found them online for $60 each, and decided to replace both, based on the experiences I read about on this forum - several people replaced one, only to have the second go bad shortly after. I did the work myself, as the sensors are easily accessible. I have been repairing my own vehicles since I was 15 in 1971, so easy for me may not be easy for you.

The engine has variable camshaft timing on the intake valves which allow the Engine Mgmt Computer (ECM) to change the way the valves work to improve power and smoothness at low, medium, and high engine RPM's. The ECM controls the camshift with a solenoid that allows or stops high pressure oil flow. The sensors tell the ECM if it is controlling the camshaft timing properly. There is a dramatic effect on power, efficiency (MPG,) and pollution if the sensors are not working.

Hope this wasn't too techie.

mvmcali
Posts: 103
Joined: Tue Nov 20, 2007 12:00 pm
Car: 2001 Infiniti QX4

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Thanks. good explanation.I was still thinking that camshafts are directly controlled by the crankshaft mechanically anad the camshaft pushes down on rocker arms and opens the valves.if valves can be opened variably now (by using solenoids and oil pressure) then why do cars even need a camshaft. cant all that electronic stuff just be controlled based on the position of the crankshaft?

Also - Can you tell me where the VTC sensors are located?The garage charged me $150 labor (for 1.5hours of work) to replace 2P1145 VTC POSITION SENSORS. I assume those sensors are in the BACK of the engine because nothing in the front (still dirty) looks like its been touched. How do you get to them?

Also - are the camshaft position sensors in the front? it looks like the left and right are shaped differently?

THX!

KALMUSI
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Joined: Sun Oct 28, 2007 7:23 pm
Car: 2001 Nissan Pathfinder 4WD 5sp

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The sensors are on the front of engine, and are identical units, but mounted at different angles. I too thought they were different when I first looked at them.

You need to remove the plastic shroud on the top of the engine in order to see the left (driver) side unit. It is mounted in a hole in the top front of the cylinder head, and picks up the position by magnetic pulses from the camshaft gear, which is in the front of the engine, and driven by the cam chain. I had to loosen the engine ground wires to get my socket wrench on the mounting bolt. The shop manual recommends cleaning the grounds, so I wire brushed them before putting them back together.

The sensors fit tight in the cylinder head, due to an o-ring gasket, so I had to jiggle and pry them out - carefully, as I didn't want to break anything, and have it fall into the engine.

The right (passenger side) is mounted in the side of the cylinder head, and it's a bit tricky to get a socket wrench on the bolt, but I did it with no skinned knuckles.

I spent about an hour to swap both parts and clean the ground terminals, and didn't get my shirt dirty. Since I had never done it before, I think my time was about double what a "pro" should need. I think the dealer charges what they can get away with, based on perceived value - in other words, they rob from the rich, the poor, and everyone in-between. Plus, I bet they didn't clean the ground wires.

The hydraulic pressure is not opening and closing the valves directly - this is still done by the camshaft, which is driven by the crankshaft. The hydraulics shift the timing of the opening of the valve by changing the relationship of the cam lobe (the pointy egg shaped part that opens the valve) to the crankshaft position. I don't think we will see a time when the camshaft goes away, and the valves are electrically operated, because it takes way too much force - the pressure would need to be huge.

On another note, as soon as I fixed the camshaft sensor code, I started to get P0171 - Lean codes and it was hesitating over 4000 RPM. Bottom line - new MAF. It's a $400 wholesale - $590 retail part for the 2001 Pathy, BUT ... per other posts in this forum, I got the '01 Maxima sensor for $78 and $20 overnight shipping - $98. This part take 5 minutes to replace - I did it in the parking lot at work. Engine is now running great - and no codes - so far! This would have been $700 - $900 at the dealer - nasty!

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88pathoffroad
Posts: 122
Joined: Sun May 20, 2007 10:13 am
Car: 1988 Nissan Pathfinder XE V6

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Quote »I was still thinking that camshafts are directly controlled by the crankshaft mechanically anad the camshaft pushes down on rocker arms and opens the valves.if valves can be opened variably now (by using solenoids and oil pressure) then why do cars even need a camshaft. cant all that electronic stuff just be controlled based on the position of the crankshaft?[/quote]Holy crap, you need to look up the difference between a camshaft and a position sensor. WTF.

With no cams there would be no valves opening. Tell me how you would open and close each valve without a camshaft.

The sensors tell the computer where each cam is at any given point and allows the computer to determine precise fuel injection, spark timing and valve timing information. This also allows the computer to determine how to achieve best economy and emissions ratios/levels.

Variable valve timing makes the CAMS more effective at producing power by allowing the computer to vary the valve timing as different RPM ranges are reached. It's a significant improvement over stationary cam timing design.

KALMUSI
Posts: 8
Joined: Sun Oct 28, 2007 7:23 pm
Car: 2001 Nissan Pathfinder 4WD 5sp

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Hey 88pathoffroad:

Did you read this whole thread? What's with the "WTF" and suggestion that I look up the difference between a camshaft and a sensor? Both quotes below from my previous posts might suggest a distinction between these components.
KALMUSI wrote:The engine has variable camshaft timing on the intake valves which allow the Engine Mgmt Computer (ECM) to change the way the valves work to improve power and smoothness at low, medium, and high engine RPM's. The ECM controls the camshift with a solenoid that allows or stops high pressure oil flow. The sensors tell the ECM if it is controlling the camshaft timing properly. There is a dramatic effect on power, efficiency (MPG,) and pollution if the sensors are not working.
KALMUSI wrote:The hydraulic pressure is not opening and closing the valves directly - this is still done by the camshaft, which is driven by the crankshaft. The hydraulics shift the timing of the opening of the valve by changing the relationship of the cam lobe (the pointy egg shaped part that opens the valve) to the crankshaft position. I don't think we will see a time when the camshaft goes away, and the valves are electrically operated, because it takes way too much force - the pressure would need to be huge.
I think we would all appreciate if you would read before you flame, and in fact, we could do without the flame all together. Your explanation of the variable valve timing is excellent, and if added to this thread without insults would have added value.

May all your sensors die tomorrow. Have a nice time driving in failsafe mode.

Oh wait - '88 Pathfinder - you are lucky, no OBDII.
Modified by KALMUSI at 7:54 PM 12/1/2007

mvmcali
Posts: 103
Joined: Tue Nov 20, 2007 12:00 pm
Car: 2001 Infiniti QX4

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LOLwell put Kalmusi. I also thought that guy was outta line but didnt bother to respond....only so much time in the day

I certainly know the diff between a camshaft and a sensor but my Q about why bother having a camshaft if you want to variably control the valve timing as a funciton of RPM is not as dumb as it sounds. I was reading that auto makers are working on advanced electro/mechanical controls to do just that.

just out of curiousity though, Im trying to understand how they currently can vary valve timing beyond it with the basic mechanical shape of the cam lobes. Ferrari apparently has cam lobes whose profile is not flat but varies along the length of the camshaft. this way they can 'slide' the camshaft' along its access and change the value timing. BUT is this the way everyone is doing it now or is there some other type of system?

KALMUSI
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Joined: Sun Oct 28, 2007 7:23 pm
Car: 2001 Nissan Pathfinder 4WD 5sp

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Here is the description of the variable valve timing, straight from the Nissan Pathfinder Service Manual:

"This mechanism hydraulically controls cam phases continuously with the fixed operating angle of the intake valve.

"The ECM receives signals such as crankshaft position, camshaft position, engine speed, and engine coolant temperature. Then, the ECM sends ON/OFF pulse duty signals to the camshaft timing control valve depending on driving status. This makes it possible to control the shut/open timing of the intake valve to increase engine torque in low/mid speed range and output in high-speed range."

There's a neat graphic, but I can't copy & paste stuff into this forum. It shows that the points where the intake valve starts to open and finally closes shifts in relation to the position of the piston, but that the duration of the opening, which is controlled by the shape of the cam lobe, does not change. I think that is the reason it's called "timing" control - the peak valve opening point is ultimately what is controlled. The pressure is adding some extra rotation to the camshaft. I think I may have read somewhere about the Ferrari approach. They probably change the angle as well, giving control of both duration and timing.

Prior to the electro-hydraulic control age (such as in my '83 BMW 633Csi) you had to change the whole camshaft if you wanted to change the valve timing. Of course you have to give up low-end torque to gain high-end HP, or vise versa.

Now that you mention it, I think I have read of BMW research into cam-free engines. They are using the spark plugs to detect pinging, have reduced the oil pressure needed for intake and exhaust variable timing, and eliminated the Mass Air Flow sensor, so developing an electric engine valve is probably just a matter of time. It was probably hard in the 60's or 70's to imagine an engine with no points and distributor - but you won't find either in the Pathfinder, and my BMW of the early 80's has no points - and the ignition timing and fuel injection pulse width is controlled by computer.

When they take away the pistons, then I'll start to worry. Actually, I've sworn off any vehicle newer than '95 - I'm tired of OBDII and replacing sensors. But I have to say, the Pathfinder is running great now that I've put in 7 new sensors. The low-end torque is huge, and I can now rev it to 6500 when I'm having BMW withdrawal. Since it's snowing like crazy here in the frozen Northeast, the BMW is in storage, and the need for rev's will set in shortly.

I still can't believe I actually found a Pathfinder with a 5 speed tranny!

Modified by KALMUSI at 8:28 PM 12/3/2007
Modified by KALMUSI at 11:09 PM 12/3/2007

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Axelpkt
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KALMUSI wrote:I still can't believe I actually found a Pathfinder with a 5 speed tranny!

Modified by KALMUSI at 8:28 PM 12/3/2007
Haha, yeah same here and I have had my 5spd for 3 years lol

mvmcali
Posts: 103
Joined: Tue Nov 20, 2007 12:00 pm
Car: 2001 Infiniti QX4

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Hate to admit it but Im having a hard time even locating the VTC sensor on the pass side of the engine. it should look exactly like the sensor on the drivers side (which I can clearly see if I remove the top cover). you wrote...

"The right (passenger side) is mounted in the side of the cylinder head, and it's a bit tricky to get a socket wrench on the bolt, but I did it with no skinned knuckles."

can you tell me where it is in relation to the 'easy to locate' coverplate for the timing chain tension adjuster?

mvmcali
Posts: 103
Joined: Tue Nov 20, 2007 12:00 pm
Car: 2001 Infiniti QX4

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sorry for the multiple questions but I will need to replace my MAF and wanted to know where did you get your Maxima substitute for $78?

BTW - I was pulling code p0171 and based on what I read in some of these forums, I removed the MAF and cleaned it with MAF cleaner. However code kicked back in at 51miles so it looks like I need to replace

KALMUSI
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Joined: Sun Oct 28, 2007 7:23 pm
Car: 2001 Nissan Pathfinder 4WD 5sp

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I'll answer both questions, but separately, starting with the easy one. The 2001 Maxima MAF is Nissan Part Number 22680-2Y001, and I ordered it from NissanParts.cc - here is a link that pulls up the part and the $78.93 price. If you click the "Order Form" button that is under the price and shipping charge pull down selection, it will take you though creating an account and placing an order.

http://www.nissanparts.cc/cart/?pn=22680-2Y001

I will try to figure out how to describe the location of the passenger side Intake VTC sensor. There is a drawing that I can extract from the Nissan Shop Manual pdf, but I have no web server to post it on.

I'll figure out something.

In my continuing saga, about a week after I replaced the MAF - a week with no "Service Engine Soon" Yellow light in my dash - I started getting P0420 codes - again. This is Catalytic Converter Efficiency Low. It can be caused by (in no particular order:)

1) Spark Plugs - which I've replaced2) MAF - replaced3) Air Leaks, intake and/or exhaust - checked4) Fuel Injectors - not checked, but I think are all good, based on engine performance.5) Cats

I ordered the new cats, but only the fronts - I figured out that the O2 sensors only measure the performance of the front. There's more to this, and I should probably start a new thread about it. It involves CARB (California.) More later.

KALMUSI
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Car: 2001 Nissan Pathfinder 4WD 5sp

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I figured it out. This forum allows us to make our email addresses visible, if desired - check your inbox, I sent a picture to mvmcali. For others, here is my description:

Start at the battery positive terminal, and look between the upper radiator hose and the smaller hose that curves around from the passenger side of the engine to the front. A smaller wiring harness branches and heads down from a bigger harness, and connects to the sensor.

If anyone would like the picture, please let me know.

mvmcali
Posts: 103
Joined: Tue Nov 20, 2007 12:00 pm
Car: 2001 Infiniti QX4

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IRA/KALMUSI - you are a genius! I replaced the MAF in my 2001 Qx4 with the 2001 Maxima MAF Nissan Part Number 22680-2Y001 and it works. no more codes. I passed smog test! total cost about $80bucks....vs the shop quote of $450 part plus $100 labor. it took me about 1/2 to install.THANKS!MVMCALI

KALMUSI
Posts: 8
Joined: Sun Oct 28, 2007 7:23 pm
Car: 2001 Nissan Pathfinder 4WD 5sp

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Thanks for the comps. I have my moments, but not genius. I can't take credit for the MAF interchangeability with the Max, as I found it in other posts on this forum (and maybe other forums.) I did dare to try it, and share that it worked, so I'm happy I could help.

I shouldn't say this (because the OBDII has ears,) but since I replaced my front Cats in Dec '07, I've been code-free.

Thanks to all who share info on this forum.

Ira
Modified by KALMUSI at 2:29 PM 6/9/2008

ifyaknowatimean
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Joined: Wed Jun 11, 2008 1:51 pm
Car: 01 Pathfinder

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To be honest, I was a little to tired to read through this, but if it hasn't been brought up yet, I recently read in my hanes manual that the cam position sensor and a distributor are the same thing. I had only ever heard of it as a distributor before, but that helped me.

path01
Posts: 15
Joined: Mon Aug 28, 2017 8:29 pm

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KALMUSI wrote:
Mon Nov 26, 2007 4:50 pm
I replaced the two Intake VTC Sensors - not to be confused with the one Camshaft Position sensor on my 2001 Pathfinder with 129K miles recently. Only one was throwing a DTC code P1140, but I found them online for $60 each, and decided to replace both, based on the experiences I read about on this forum - several people replaced one, only to have the second go bad shortly after. I did the work myself, as the sensors are easily accessible. I have been repairing my own vehicles since I was 15 in 1971, so easy for me may not be easy for you.

The engine has variable camshaft timing on the intake valves which allow the Engine Mgmt Computer (ECM) to change the way the valves work to improve power and smoothness at low, medium, and high engine RPM's. The ECM controls the camshift with a solenoid that allows or stops high pressure oil flow. The sensors tell the ECM if it is controlling the camshaft timing properly. There is a dramatic effect on power, efficiency (MPG,) and pollution if the sensors are not working.

Hope this wasn't too techie.
pretty sure VTC sensor is same as camshaft position sensor. If not, please someone point to each on an auto parts site. Ive tried.


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