94 240 conv with AT shift problems

[NISTECH]

maik21 you got something different going on. The rest of you check your ground on the solonoid harness, It may be inside the pan with the solonoid pack. make sure the crimp on the wires is secure and the wires dont move back and forth in the crimp on the lug. If it does ,unbolt it and clean it thouroughly with brake clean ,dry it thouroughly , solider it to the crimp,make sure your solider flows properly into the wire. Rebolt it on reassemble the car and recheck it.

The led on the light only indicates voltage is present on that wire it does not indicate the tcm is not sending a signal. What it means is the load is not being used anywhere else in the circuit. Which could be a poor connection to ground at the solonoids. I am going to take a look at the service manual and see if I can be more specific on the grounds location.

[NISTECH]

comforimed they are on the solonoid packs in the trans, check both of them , but your solonoid a and b use the same ground and are in a cluster of 3 solonoids all 3 solonoids share the same ground lug.

[240ROCKER]

NISTECH,Thanks so much for your help on this. Could you please help me to understand by what you meant by the following: "The LED on the light only indicates voltage is present on that wire it does not indicate the tcm is not sending a signal. What it means is the load is not being used anywhere else in the circuit."

Electronics is my background and I don't understand what you are trying to tell me here. Is the transmission looking for a constant voltage to shift or is it looking for some sort of pulse??

Here is my understanding of what the LED I installed on pin 6 of the TCM is telling me. During normal operation, when the transmission is in first gear, the LED is 'ON' and right before it shifts to second the LED turns 'OFF' which tells the 1st to 2nd shift solenoid to shift...right? When my transmission doesn't want to shift to second the LED remains 'ON' which means the 1st to 2nd shift solenoid didn't get the command to shift. Is this a correct assumption on my part?

Now you also said that the load is not being used anywhere else in the circuit. This is the thing I'm having a problem trying to understand what you are saying. Are you saying that if the connection from the solenoid to ground has an intermiitent connection to ground, then it is not completeing the circuit and therefore there is no load because the solenoid circuit to ground is open?

Have you seen this problem before with the intermittent shift on and 240's you have serviced????

This just might be the big break we all have been looking for. I will be dropping the pan in a few days to check my ground out and to solder it.

Thanks again!!!!!!!!240ROCKER

[NISTECH]

I Have pondered this problem on and off throughout the day. I too have an electronics background before I got into this buisness. I keep analizing the senarios I keep coming to a dead end since the TCM supplies the power to the solonoid rather then Grounding it which is what control units typically do on nissans. I have not seen this problem on the 240s but have replaced solonoid packs for shift related problems on 240s. I brought that potential problem to the table for 2 reasons one is grounds tend to be a fairly common problem with nissans but also based what I told you on the operation of the typical control unit operation with other components on the engine. Hold off on doing this ground repiar/check till I can review the circuit in depth a bit more. I also brought this to the table since a recent bulliten came out on the altima for a ground issue similar to what I mentioned about the ground as it is throwing a solonoid code and causeing a shift problem from 1 to 2.

[240ROCKER]

It's hard for me to suspect the solenoid being bad because it isn't throwing any error codes back at all. That is why I tend to agree with you NISTECH that I have a ground problem. I just wish I could be sure that is what it is before I have to take the time to drop the pan and valve body to get at the solenoid and the ground terminal. It also makes perfect sense that it's possible that the one wire from the shift solenoid 'A' is not crimped very well in the terminal or the ground terminal is loose. However, if the terminal was loose, I would think I would be having problems with other shifts as well and not just the 1st to 2nd shift.

So can you think of anyway I can verify that this is a grounding issue without going through the labor of dropping the pan and valve body as mentioned previously? Is there something else I can monitor on the TCM perhaps????

Thanks again!240ROCKER

[NISTECH]

I just got out of the service manual and stumbled across somthing I wasnt thinking of could be the problem. For the hell of it reach down by your gas pedal and unplug the kick down switch for a few days and see if your problem is gone. Its an easy test and the connector is easily accessable. I am wondering if it is sending a signal to kick it down when it shouldn't. I will continue to research but stay away from the panthing for the time being cause logically [after deep thought of its operation] it dosent make since that ground is the problem since the TCM supplies the power not the ground.

Have any of you takin it to the dealer and had them pull it up on consult and check for codes in the TCM? its not the same as checking codes in the ECM.

[240ROCKER]

Yeah...When this problem first started happening a couple of years ago, I immediately took it to a dealer. Of course it wouldn't act up for them and they couldn't find anything wrong, so they suggested a transmission flush. I have since taken it to another foreign car specialist and they couldn't find anything wrong either.

I will remove the kick-down switch and try that. Regarding your comment about the solenoid being controlled by the power signal from the TCM. If the solenoids ground was not a good connection, as you previously stated, then the solenoid will not shift because the circuit to ground isn't completed and therefore you would have an open circuit. Meaning that the transmission wouldn't even see the solenoid. Right???

This is why I still think that the ground issue could be the culprit!!!!What are your thoughts on this?

240ROCKER

Modified by 240ROCKER at 9:39 AM 3/30/2005
Modified by 240ROCKER at 9:43 AM 3/30/2005

[NISTECH]

the solonoid is always applied when its in 1st gear, when it shifts to second it turns the solonoid off(takes away the supplied voltage. For some reason its not taking away that voltage. I did find a good page in the service manual which lists all the inputs and outputs for the tcm. I need to go through it and see what is the potential problems and what wont effect the shift decision of the TCM. I have not done it yet and might later tonoght as I have to do some karate with my kids tonight. Both of them are goin up in belts tonight.pretty soon they gonna be able to kick my butt...lol

[ncaa1969]

NISTECH,Thanks for joining in our quest for a solution to this apparently common problem. We need the help! I disconnected the kick-down switch but it had no affect. The transmission hung up in first gear same as always.

I had suspected the AT fluid temerature sensor, but I monitored it and there was smooth steady change in voltage as the transmission warmed up - matched the service manual range from hot to cold. If it is of any value, the gear hangup always occurred when the voltage across the sensor was about .77 to .8 volts. Just to be sure, I cut the temperature sensor feed to the TCU and substituted a 2.5K ohm resistor so the TCU would think the transmission was still cold. No help - still hungup in first. Did the same with a low resistor to simulate fully warmed up - no help - still hungup at the same 5-7 minutes after a cold start.

Today I hooked my multimeter across the Throttle Position Sensor as soon as the hangup in first gear started. I got some off the wall readings, twice to three times normal. I should have seen about .5 volts at closed throttle but was getting about 1.3V with wide fluctuation. And the meter jumped to over 6 V at 1/4 throttle. It very well could have been due to one or both of my probes being loose. But within minutes I was getting proper readings (.44 V at closed throttle, about 1.0 V at 1/4 throttle) (it is a new TPS that bench-checked fine before installation)

I'll run the TPS test again tomorrow - I have to wait for full cool down.

Thanks again for your help on this. Greg (ncaa1969)

[NISTECH]

run a wire from the tps tp the inside of the car and watch the voltage changes while your driving and see if it goes hay wire while driving.

Kick down is a negetive then.

[NISTECH]

Ok here is a diagram of all the electrical components the TCM uses to control the trans.

There is a test i would like someone to conduct. If you have a multimeter that has AC capabilities I would like you to back probe pin 25 of the TCM. Measure between that terminal and ground. Watch it as you drive the vehicle see if the signal goes haywire or to 0v when it wont shift. This is the revolution sensor for the trans. it is not the revolution sensor for the ECM. This is an AC volts generating sensor. it should climb from 0v it a stop to over one volt at about 19mph and should steadily increase as you drive. You guys are going to have to start testing things till you find the one that is sending an eronious signal. The TPs is still a concern if it in fact is glitching still do the test on that as well.

[240ROCKER]

Hey NISTECH congrats on your kids karate belt upgrade.

Here is a quick list of things that I have done in the order that I have done them to try to fix what is going on with my transmission, but to no avail.

1. Replace ATF and change filter2. Transmission Flush by the Nissan Dealer3 TPS replacement4. TCM replacement5. Remove kick-down switch

Here is something that someone did to fix their transmission problem and still had the problem!!!!1. Transmission rebuild which included a soleniod pack replacement but did not include a rebuild of the valve body. After the rebuild was completed, it took about a month before the problem started happening again, but it did return.

240ROCKER
Modified by 240ROCKER at 10:45 AM 3/31/2005

[NISTECH]

This is an electrical problem no doubt about it. But tests need to be done on components that effect the TCM's decision to turn off the A solonoid. Either its not seeing the load of the signal when it got it on or its not seeing the appropriate time to shift to 2nd[Throttle input,vehicle speed]

[240ROCKER]

Well...I got bored today, so I went to my friendly neighborhood transmission specialist again and I had him drop the pan and we looked at the solenoid pack and the ground terminal for it. Guess what??? The ground terminal harness was already soldered and there wasn't any evidence of a cold solder joint or an intermittent connection. He also had a set of used but good solenoids that we put on as well. After leaving his shop, I drove about five miles down the road and I started having the intermittent shift problem! Ugh!!!!!! At least now we can rule out the solenoids and the ground circuit for them.

NISTECH, I saw your latest reply after I did this, (that's what I get for getting antsy and jumping the gun ) so now I'm going to put a DMM on the revolution sensor on the TCM, as suggested, and see what voltage I get when it starts acting up. Has anyone else had a chance to do this yet??? What else can I possibly monitor NISTECH???? We are running out of things to check!!!!!

240ROCKER

[ncaa1969]

240ROCKER, NISTECH,

I ran the test on my TPS and got normal readings, not the fluctuating ones I saw briefly yesterday - must have been a loose back probe. My cheap DMM doesn't cover AC so I can't run the revolution sensor test.ncaa1969

[ncaa1969]

Found a Multi-meter with AC voltage capability. hooked it up to the Revolution Sensor feed and went for a run. I got no reading throughout the drive on lowest scale of 200V which reads to the tenth of a volt. Triple checked the probes. I did switch to DC volts and read about .24 volts with no change with change in speed.

My manual says to check resistance across the revolution sensor. Manual says normal range is 500 - 650 ohms. Mine reads 860 ohms.

I'll be interested in 240ROCKER's results.

Changing the sensor looks like a chore. Need to support the transmission, drop the rear cross member and lower the transmission "as far as possible" to get access.Greg (ncaa1969)

[NISTECH]

By the way greg I am working out of a 93/94 service manual as its the oldest i have. test procedures may be listed differently in both manuals. go to the self diagnostics section for a trans code for the rev sensor ,that is the test I was having you run. The problem with some of these sensors is the computer only looks for 0v or constant max voltage nothing in between when it decides to set a code. since you "A" resitance it means the TCM sees something and wont throw a code.

[NISTECH]

Also note the terminal orientation on the 2 yrs might be different so take that into account when doing this. you may have to reffrence your manuals for the correct terminal arrangemnet.

[ncaa1969]

NISTECH,I have a 92 manual and terminal pins are the same.For whatever reason, my self diagnostic test does not work to give me the flickers on the OD on/off light, so I can't read codes to see if it indicates a problem with the revolution sensor. I have not pulled the panel to back probe on the TCU harness, I have been probing under the hood at the connectors by the fuse box. Can I get codes directly off the TCU? If so, how?I'm encouraged by looking at the revolution sensor as the probable culprit here because:1. the resistance reading on mine is out of range.2. no voltage present on terminal 25 during driving.3. My manual include a "Symptoms Table" and the revolution sensor is listed as the third most probable source for not shfting fom 1 to 2, and is listed as the second most probable for "too high a gear change point from 1 to 2"4. It is logical that the TCU would not shift up to second from first if it wasn't "sensing" increasing revolutions as the car accelerated.But I'm reluctant to plunk down the $150 quoted by my local Nissan dealer for a new revolution sensor, without someone else duplicating my findings. Perhaps 240ROCKER will get some similar failure readings on the revolution sensor. In the meantime, I'll call my Nissan parts department and see if they used to same revolution sensor on other Nissan transmissions (to broaden my chances of picking up a low mileage one at a junk yard.)Thanks again for your help and suggestions. Please send me more tasking and I'll try any tests within my ability. Greg

[240ROCKER]

Hey guys,I haven't been able to backprobe pin '25' of the TCM yet. I'll be doing that this weekend. However, I did manage to read the resistance rating from pin '1' to pin '2' on the revolutions sensor and I'm getting a reading of 831 ohms. Like your reading Greg, mine is out of tolerance too. I too called my Nissan dealer and he quoted me $143.61 plus 11.49 tax. Geeeesh!!! This thing is expensive. It doesn't look like to bad of a job to replace, but I want to be sure that this out of range resistance reading is indeed stating that this sensor is bad.

I was hoping that my Nissan dealer had one in stock so I could test its resistance but he didn't because this is a part they don't usually stock because he had never had to have one replaced before.

Looking around on this forum and others, I found several threads on some of the Infiniti cars that had this intermittent problem from 1st to 2nd and the fix seemed to be replacing the revolutions sensor.

Does anyone know where we can get discounted Nissan OEM new parts on the web? I have bought some before from some internet dealers, but I can't remember where!

I will do the O/D diagnostics test and I will also do the backprobe on pin '25' of the TCM and let everyone know what I find.

I really think that we are onto something now guys. Could this be the answer we have been looking for......????????????

240ROCKER

[NISTECH]

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]

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 transmission 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]

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]

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]

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]

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]

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

[ncaa1969]

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]

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]

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.