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P0702 output shaft revolution sensor

16K views 47 replies 4 participants last post by  rogoman 
#1 ·
I'm back after pulling my hair out over this issue for some time now.

Symptom: It seems to be specific to me sitting still. I can drive the car down the road accelerating, holding speed, and slowing down with no issues at all.
However, if I sit at a red light then take of when it turns green there are times when it will refuse to shift out of 1st gear. I then have to pop the car into neutral shut it off and start it back up. After that it will drive fine. Also sometimes after I restart the car like that the O/D light will blink a few times then shut off and the car goes back to normal.

This problem originated around the same time as my old alternator going out. (The alternator's voltage would bounce back and forth between 12.5v and 16.5v.).

Fixes: I replaced the "Speed Sensor" or (output shaft revolution sensor depending on where you look it up). The problem did not go away at all. So I decided to put the old one back in thinking that the new one was just a piece of junk from Autozone. Also because I replaced the old one while the alternator had still been bouncing voltage like that thinking that maybe it was just throwing off the readings by the vehicle. Well the issue is that the problem is still there.

At this point I'm starting to wonder if I have a bad TCM because both Speed sensors work well enough that the speedometer registers the vehicles speed accurately and the needle moves according to how fast I'm going. I haven't seen any hiccups in it's movement either.

Anyone else have any ideas?

Note: It doesn't seem like this is a common problem because I find this issue with a lot of other vehicles.... just not Nissans.
 
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#2 ·
If the alternator voltage is still bouncing around between 12.5 and 16.5, then you've got a problem there. At idle the voltage should HOLD STEADY somewhere between 13.2 - 15 volts. When a charging system is not charging, or overcharging, a lot of "strange" things can occur. It's not uncommon to see a multiple of stored trouble codes in the ECU memory. So, whenever a car is setting a multiple of trouble codes, idling funny or stalling, or anything out of the "norm," test the charging system before you start pulling hairs!
 
#3 ·
I have replaced the alternator and it hold steady at 15.1v. It's not ideal but it's better than the 16+ volts it was reaching. I only have 1 trouble code that comes up over and over which is the P0702 code. I did some thinking and someone also mentioned to me before that maybe the TCU failed. Tomorrow I'm going to see about removing it and having a look at it to see if my suspicions are true. A few months ago I could smell something that reminds me of burning electronics. It's a very unmistakable smell that I've experienced before back when my 99 Ranger's ECM shorted and a chip on it fried.

A little side note. My reason for thinking it may be the TCU is not only because of the smell. It's also because this problem didn't start happening until well after the last alternator went bad. I think it was right before I finally replaced it. So I'm thinking that the voltage fluctuation may have fried something in there. Does this sound possible to you or is there some sort of safeguard to prevent this from happening?
 
#4 ·
I would say that the 16.5 volts sure could have fried the TCU. As far as I know, there's no safeguard for the TCU. Even the constant 15.1 v shouldn't be happening; the voltage should be sitting around 13+ with a fully charged battery. I think you may have something else that's wrong like a bad ground.
 
#6 ·
So I took out my TCM and and opened it up. I didn't find any physical damage to it. So if it is damaged then its all internal. Maybe I'm missing something when I looked at it initially so here's a bunch of pictures I took of it.











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#8 ·
So I decided to see if I could get my transmission to run a diagnostic as instructed in the Factory Service Manual. Wouldn't work at all.

I even thought that I would try the SES tooless diagnostic where you turn the ignition on for 3 seconds, pump the gas peddle 5 times in under 5 seconds, then wait 7 seconds, then press and hold the gas peddle for 10 seconds. I even used a watch to make sure the seconds were exact multiple times and nothing, it just refuses to do anything.
 
#10 ·
I've got no idea. The car runs and runs fine, but it will spaz out. I did notice that when the e-fans came on today the engine bogged. I think I'm going to look for more grounds.

So far I've cleaned the battery terminals
The one underneath the battery
The one on the transmission
The one on the engine block
and I added another ground from the alternator to the engine block

I just found another ground on the left side of the vehicle literally right to the left of the alternator pulley on the wheel well that I'm going to look at tomorrow. There has to be more grounds though.
 
#12 ·
Wooooo! I finally found the ground problem... I think. [emoji2]



The first owner put that on the car. I just noticed that it was loose..... Very loose.. So I'm going to take it apart after work and spray the wires with some safety solvent and try to clean it up and out it back together.

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#15 ·
Well, it was minor stuff like if I had my car in park and I rolled my windows up the engine would idle rough. If it was in park and on a slope and the car had any kind of weight on the parking gear the engine would idle rough. Stuff like that. If there was a decent electrical load the engine would idle rough. If I had to put my foot into it the car would feel under powered compared to how it should be.

The transmission problem I am having actually only happens if I'm sitting at a red light for a while. It doesn't lock me to 1st gear if I'm moving in 1st gear. However if I am sitting at a red light the car will lock me into 1st and when I take off it won't shift. But that only happens while at idle in gear at a red light. Now I have noticed that it doesn't seem to want to lock the torque converter sometimes while on the highway.
 
#16 ·
So a friend of mine has been helping me by looking into the diagrams for the speed sensor circuit. According to his info the circuit goes as follows.

Rotation Sensor -> Gauge Cluster -> TCM

This explains why my gauges all seem to work great but still have a P0720 SES.

So this weekend I'll break out my multimeter again and check the wires from the gauge cluster to the TCU for continuity.

I am also going to order a Bluetooth reader to try and pull I to while I'm driving to see if I can dig anything up there as well. I found a BAFX reader for 21 bucks that seems to have quite a few good reviews. Will report back later on what I dig up.

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#18 ·
I don't have it yet but I will be able to as well as get data in real time. Also it may be a coincidence but yesterday I pulled the instrument cluster to see if the wires were loose back there. Everything looked fine so I out it back and immediately got locked into 1st. I did a quick restart on the car and it drove fine this morning it did it again on my way to work so I'm starting to think that my problem is a short either in the cluster or the wiring between the cluster and the TCU.

Will more digging this week/weekend.

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#21 ·
At this point I suspect that I have another bad alternator. I didn't get a chance to check out the circuit board of the gauge cluster but I did do a quick voltage check on the cat and it is producing higher and higher voltage by the week. It was at 15.1 when I fixed all my ground issues. Last week it was at 15.2. Last night it was at 15.3v

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#22 ·
So here is what I've got so far after replacing the battery in my multimeter.


The multimeter that I am using for all of this.


The voltage with the positive lead on the alternator stud and the negative lead on the negative battery terminal.


Both leads on the respective battery terminals.

Now what I have also noticed is that when I shut the car off the voltage doesn't suddenly drop to 12.x volts at the battery. The voltage stays at 13.35 and slowly bleeds off .01v every couple of seconds.

I'm beginning to wonder if it isn't the battery itself. If I measure ohms between the alternator wire at the alternator and the battery terminal I get 0.8. My understanding is that this is too high and it should be 0.2.

All grounds slow 0L or 0.2 depending on distance.

Any ideas at all? Maybe @jdg knows?

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#23 · (Edited)
OK, it wouldn't let me edit my old post in mobile view so I will say it here. After letting it sit for a while my battery dropped to 12.60v with the car off.

So I did some more testing. I watched a video where this guy had shown that his car wouldn't charge if the moved the plug connected to the alternator. Not sure what it's called.

Now, that being said I decided to go look at mine for giggles. Mine doesn't have that problem. However I did notice that if I pulled that plug while the car is running that it takes aprox 30 seconds before my alternator to respond. During this time it will continue to supply 15.35v at the positive post on the alternator. After that time it will drop down to 12.18v at the battery. I decided to leave it running for a while to see just what happens. I noticed that the battery light did not come on at all and that the car stereo was still on through all this which means it should have put a drain on the battery. I can also say that the car continued to run at 12.18v so I decided to turn the headlights on and flick the brights switch to on. The voltage dropped to 12.10v then slowly rise to 12.15v where it sat. All the while the car didn't die.

Oh, another thing I noticed is that the car ran way smoother at 12.18v than with the plug connected to the alternator which would have had it producing 15.35 at the alternator's positive post. Even in reverse the car didn't shutter like it does when it gets more voltage. I think it's safe to say that my alternator is yet another POS from Autozone.
 
#29 ·
Well I officially fold. I give up on this steaming pile of crap. I've replaced this alternator twice since I've had it making it the 5th alternator that has been on it. I've fixed all the grounds that I could find. I've checked all the wires and even the battery. I am thoroughly convinced that it is the alternator and at this point with the 5th one I have little reason to think that replacing the alternator will do anything. The alternator currently installed began charging at 14.77v but over the last 2 days it has crept up to 14.89v and now 15.03v.

I've even noticed that if I took the negative ground terminal.off the battery post with it running the alternator's output will not change. At this point I just give up on fixing it.
 
#30 ·
While I'm no expert in electronics when it comes to cars it sounds like something in your car is frying the alternator. I know my uncles 1997 Sentra did that though I cant remember what was it that fixed this same(sort of) issue for him. Have you checked every single electrical wiring? At this point I'd take it to a mechanic

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#36 ·
So after doing some more digging I'm starting to wonder. I saw a diagram of the charging system of the SR20 system which shows a 30a fuse on the sense line off the alternator. I can't find the damn thing. I can't find where it is, should, or would be.

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#38 · (Edited)
It's fixed! So for anyone who may want to know. The issue was actually a combo of things.

First off if your horn quits working and it constantly blows fuses there are threads that will tell you to just run a new horn wire from the fuse to the relay. You can do this but keep in mind that NISSAN RAN THE ALTERNATOR SENSE WIRE (GREEN WITH A BLACK STRIPE) TO THAT HORN LINE. This means that you will have to cut and tie that green and black wire into the new horn wire otherwise your alternator will not see the 12v current that it is looking for from the battery and it will charge at full force. In my case this was 16+ volts.

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