94 240 conv with AT shift problems

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NISTECH
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Re: (ncaa1969)

Postby NISTECH » Fri Apr 01, 2005 3:56 pm

As far as diag mode without consult the only way to do it is the way your doing it. For the sensor go to a wreakin yard and test it with you DVOM if the ohms are with in spec it should be a good sensor regardless of the milage of the car. Here is the diagnosis procedure for the rev sensor per the 93 service manual, it should be on or around the same page in your manual. And remember if the TCM sees any signal from the sensor other then 0v or max volts weather its logical or not it wont throw a code. Meaning even if you were able to check for codes it may not throw one if the sensor is bad.


240ROCKER
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Re: (240ROCKER)

Postby 240ROCKER » Sat Apr 02, 2005 6:31 am

I have emailed everyone in this thread who has experienced this problem, but not posted here, with the intermittent shift asking them to check their resistance across pins '1' and '2' of the revolutions sensor. I want to gather as much data as I can to prove this theory.

Now, I would also like anyone who has a good working tranny without the problem to check their resistance as well, so I can prove to myself that a good revolutions sensor does indeed fall in the 500-650 ohm range!

Thanks so much!!!!!!240ROCKER

240ROCKER
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Re: (NISTECH)

Postby 240ROCKER » Mon Apr 04, 2005 3:32 am

Hey NISTECH,I have personally contacted some of the people on this forum who are having this shift problem. Everyone who has checked their resistance from pin '1' to pin '2' has had a reading of 720 on up. Mine has 831 and others have had as high as 860. Do you think that since this is out of tolerance from the service manual's 500-650 ohms that this would mean our revolution sensors are bad???? THe person who had 720 said that his didn't happen everyday, but that it did happen. It seems that since the weather has gotten warmer here, mine is happening alot more often too.

240ROCKER

NISTECH
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Re: (240ROCKER)

Postby NISTECH » Mon Apr 04, 2005 3:45 am

what needs to be done is one of 2 things, go to a wrecking yard with your ohm meter in hand and check some till you find one that is within tolorance. buy that one and test it in your own car. if it works you found your problem.

Option 2 find someone who does not have this problem AT ALL and have them test theirs to see if their sensor is with in or much closer to spec.

NISTECH
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Postby NISTECH » Tue Apr 05, 2005 4:09 pm

Update!! got a little info and a real test for you to perform to nip this problem in the butt.

The revolution sensor is the governor of your transmission, a govenor is what decides to shift the gears. The common complaint from customers when this fails is "NO UPSHIFT FROM FIRST INTERMITTENLY" Sound familier? This sensor is the primary sensor that is used to decide to shift the trans. But guess what? It has a back up. That back up is the speed sensor in your dash which gets its signal form the speed pick up in the trans. When it goes to the secondary sensor it has seen a complete failure of the other sensor. Your sensor generates a voltage and it slowly increases as you speed up. if you had additional resistance in the circuit the voltage to the TCM would be lower hence a no shift or much later shift. Your resistance reading indicates you have a higher then spec resistance. What this means is your sensor is your problem. Since the sensor hasnt completely failed the TCM is not going to the back up.

Here is the good stuff.Here is where we are going to make it go to the back up. Flat out disconnect the rev sensor and drive it over enough period of time to determine that the problem no longer exists. Keep in mind your speedometer has to be working since it is the back up. If you do this and the car drives without incedent replace the sensor and plug it back in. Note you will get a flashing O/D light while its unplugged when you first turn the key on. just ignore it for now. It will drive fine without it plugged in.

swadude
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Re: (NISTECH)

Postby swadude » Wed Apr 06, 2005 3:12 am

I've been following this thread for several weeks hoping one of you tech savy guys would find an answer, sounds like this might be it. I'm not a tech guy and I don't have a manual, can one of you tell me where to find the Revolutions Sensor and how to disconnect it?Thanks.

NISTECH
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Re: (swadude)

Postby NISTECH » Wed Apr 06, 2005 3:29 am

Here it is. The connector should be gray in color.

ncaa1969
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Re: (NISTECH)

Postby ncaa1969 » Thu Apr 07, 2005 8:48 am

NISTECH,After two days driving and several opportunities for failure, the tranmission is operating just fine with the revolution sensor disconnected.

Congrats and thanks for getting to the bottom of this.

now I'll bite the bullet and buy a new revolution sensor (and report here if everything works properly).

Thanks again, Greg

240ROCKER
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Re: (ncaa1969)

Postby 240ROCKER » Thu Apr 07, 2005 4:04 pm

Well...here is what I have found! Since I disconnected the revolutions sensor to test the resistance across pins '1' and '2', I have not had the problem. This means all I did was reseat the connector and everything is fine. I'm going on six days without any problem. So...those of you with this problem might wanna try and clean your connector with contact cleaner or brake fluid, before replacing the revolutions sensor and be sure to put some non-corrosion grease on it before re-connecting it!

A BIG THANK YOU goes out to NISTECH and everyone else who contributed to the findings!!! I knew we could do it!!!!!!!!!

240ROCKER

swadude
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Re: (240ROCKER)

Postby swadude » Fri Apr 08, 2005 4:04 am

Same thing here. I disconnected cleaned and reconnected every connector under the hood that I could get apart, (at the time I didn't know which one was the rev sensor). That was about 8 days ago and I have not had shift problem yet.

If the problem comes back can I disconnect the rev sens and just let it work on the back up mode without hurting the car, or should I get a new rev sensor?

The information from the guys on this board has saved me lots of time and $$$$, Thanks.

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CDE
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Postby CDE » Fri Apr 15, 2005 3:51 pm

This thread rocks.

I have been having some tranny problems (89 s13 auto), and they have been giving me a lot of grey hair. My 1st - 2nd is a rough shift 90% of the time and also in the top gear, it starts to shake/shudder/hesitate after going over 80 kph. I'm going to go clean that thing right now, and then as my test I will drive to my local electrical store and pick myself up a nice voltmeter. It really sucks because I haven't been able to drive on the high way (do to my problem about 80kph) so it takes a lot more time getting to work and stuff.

I'll let you guys know if it also fixes that problem....

But really I would like to switch over to a 5 sp. I really miss my stick shift (Just got rid of my corolla GT-s 5spd)....but it would sure be nice to at least have a working auto! The same thing has happened to me know...I have taken it to a mechanic (didn't act up for him) and then a transmission specialist (didn't act up there either) and a dealer (*suprise* didn't act up there either). I swear my Nissan is messing with my head sometimes.

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CDE
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Re: (CDE)

Postby CDE » Fri Apr 15, 2005 4:46 pm

OK, my car seems to be a little different than that diagram...Just wondering what one is the rev sensor/plug. MSN is fussy and won't let me link my photo's so it's the last photo on this link:

Also, there's another picture on there that I was wondering about. It's the fourth pic in that link. Just wondering if there's supposed to be a ground coming off that plug near my dist. cap or something...



The 1, 2, 3 are all plugs that are under one another. just wondering if it's one of those or the circled one.

the mysterious connector that nothing is connected to...

Turns out that I can link them from my MSN website. yay.

Thanks,Chris

Modified by CDE at 8:00 PM 4/15/2005
Modified by CDE at 8:03 PM 4/15/2005

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CDE
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Postby CDE » Fri Apr 15, 2005 8:33 pm

I'm working on getting a better FSM so I don't have to ask these silly questions :P

NISTECH
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Postby NISTECH » Sat Apr 16, 2005 1:50 am

pic one, it looks like its 2 pic two ,nothing goes there

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CDE
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Re: (NISTECH)

Postby CDE » Sat Apr 16, 2005 7:40 pm

Well, I unplugged #2 and has some weird results...it was stuck in 3rd even at fast speeds, and would upshift to OD when I tried to accelerate. I also just unplugged the #1 plug and that didnt change anything. It seems to do it less vigorously so I'm going to spray them real good with cleaner...and I'm still working on getting a feeler gauge to test the TPS (other thread in nissan online mechanic) or even a volt meter.

oldbald_sarge
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Re: (NISTECH)

Postby oldbald_sarge » Sun Apr 17, 2005 3:13 am

Thanks to all the techs that worked on this problem. All I did so far was unplug the sensor, and it has run just fine. I'm really surprised that it was not enough of an issue all this time for someone to call on the techs for help. Thanks again to everyone.

NISTECH
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Re: (CDE)

Postby NISTECH » Sun Apr 17, 2005 4:13 am

CDE wrote:Well, I unplugged #2 and has some weird results...it was stuck in 3rd even at fast speeds, and would upshift to OD when I tried to accelerate. I also just unplugged the #1 plug and that didnt change anything. It seems to do it less vigorously so I'm going to spray them real good with cleaner...and I'm still working on getting a feeler gauge to test the TPS (other thread in nissan online mechanic) or even a volt meter.
does your speedometer work? If it doesnt you will put the car in failsafe [3rd gear] as it wont have a back up sensor to goto for speed input.

NISTECH
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Postby NISTECH » Sun Apr 17, 2005 4:15 am

if you want to find the connector for it,go under your car and loacte the small black sensor near the tail housing[not the bottom one thats for your speedomter] It should be near the top. follow the harness back to its connector.

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CDE
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Re: (NISTECH)

Postby CDE » Sun Apr 17, 2005 8:18 am

Yes, I just picked up a brand new electronic speedo head about 2 weeks ago.

The new speedo didn't change much like I was hoping it would.

I found how to do a self diagnostic using the OD light, but my light isn't working...(the od light next to the hazard lights). It doesn't come on when I take OD off. The cruise light also doesn't work (but the cruise does now with the new speedo head).


MrUnderhill
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Re: (oldbald_sarge)

Postby MrUnderhill » Wed Apr 20, 2005 1:59 pm

Well, if anyone remains unconvinced that the revolutions sensor (or some aspect of it) is the cause of our problems, let me weigh in with my experience. I unplugged the connector yesterday and have been driving for 2 days now with no shift problems whatsoever. Just curious - for those of you who cleaned the connector and then reconnected it, how did you do it? I was not sure about the posts talking about contact cleaner, brake fluid and non-corrosive grease - did you clean the exterior only, pour it in the connector, where does the grease go, etc.? I'd like to clean the connector and plug it back in to see if I have the shift problem again (bad sensor) or not (dirty connector).

A huge thank you to all of you who took the time and made the effort to get to the bottom of this. For those of us who are not tech-savvy, you have saved us a lot of money getting to the bottom of this. Thanks again.

flint
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which plug

Postby flint » Thu Apr 21, 2005 10:40 am

Mine is exactly like yours and I unplugged #1 and that`s the correct one. Only been 24 hours, but so far so good. Good luck, Flint.

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CDE
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Re: which plug (flint)

Postby CDE » Thu Apr 21, 2005 8:56 pm

#1 on my pic?I tried that one but it did not fix it for me. I'm thinking it's the TPS now...I finally bought a volt meter so I can do a test on the ATCU soon as I can...

TofuTechS13
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Re: which plug (CDE)

Postby TofuTechS13 » Fri Apr 22, 2005 1:41 pm

i'm having a shifting problem also. No matter if i lightly tap on the gas or floor it, the only time it shifts is at certain speeds, 1st to 2nd at 25 mph, 2nd to 3rd at 46 mph, and 3rd to 4th at around 60 mph. I read this whole article but i'm unsure whether this is related to the intermittent shifting. Do i do the same things as listed in this thread or is it some other problem?

NISTECH
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Postby NISTECH » Fri Apr 22, 2005 1:51 pm

I think your dealing with something other, but your shift points look ok.

Check your tps.

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CDE
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Re: (NISTECH)

Postby CDE » Mon Apr 25, 2005 9:33 pm

Hey dude,

I just have a few questions. I ripped apart my passenger side kicker panel - removed the panel, the fan motor and the bottom half of the fan ducts so I could get at the ATCU. Now, I've taken pictures of what I've found thus far...

This is I think the ATCU, which was right above the bigger elec. control unit on the side wall right near the front. My manual wasn't the greatest but I'm pretty sure that's the atcu.

This is where it gets weird. I went to test the voltages across the TPS but...there was no power or ground wire for the tps, according to my manual.

These were the 2 plugs from the unit:



According to the manual, pin 3 and 5 are supposed to be the power to the TPS...but as you can see from the picture below, there are NO wires in those spots! It's supposed to be a 12 volt reading or whatever my battery is at, and then the tps is closed throttle .4-4 Open throttle...



I guess my main question is if I'm checking the right component and pins. Also, can I just unplug the connections and test without them plugged in, or do they have to be plugged in.

I'm going to give it another go tomorrow morning...It was so damn hot this afternoon I had to jump into the 60* pool to cool off....that really took my breath away It's finally been nice enough to get the pool up and runnin

NISTECH
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Postby NISTECH » Tue Apr 26, 2005 2:09 am

Whoa your an ambitious one!! just test it at the TPS itself, dont worry about testing it at the control unit just yet. I dont have a 240 service manual that old on hand so I can not verify what pins your looking at.

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CDE
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Re: (NISTECH)

Postby CDE » Tue Apr 26, 2005 9:55 am

NISTECH wrote:Whoa your an ambitious one!! just test it at the TPS itself, dont worry about testing it at the control unit just yet. I dont have a 240 service manual that old on hand so I can not verify what pins your looking at.


Um...where exactly is it?

I think I have a good idea but I'm going to just start to prod and poke...

Another question....can I buy 1 screw at the dealership 'cause I lost one that held the fan unit in place. The damn thing didn't stick to my magnetic ratchet like it should have and fell into a void that has no return I will probrably just substitute a less important screw but I just don't want anything to rattle around.

NISTECH
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Postby NISTECH » Tue Apr 26, 2005 1:54 pm

it is on the drivers side of the throttle body toward the engine block. kinda a bugger to get to but you shouldnt have to reposition much to gain access.

Yes you can buy just one screw at the dealer.

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CDE
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Re: (NISTECH)

Postby CDE » Tue Apr 26, 2005 3:28 pm

Thanks

Is it easier to get to going from the top or bottom?

I don't have time today and am losing light so I'm just going to do it tomorrow morning.
Modified by CDE at 11:08 PM 4/26/2005

NISTECH
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Postby NISTECH » Tue Apr 26, 2005 4:26 pm

from the top. over the intake tube.


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