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.

Electronics is my background and I don't understand what you are trying to tell me here. Is the tranny 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 tranny 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 tranny 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

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

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.

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 tranny 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

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)

Kick down is a negetive then.

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.

Attachment: 240ATcontrol.jpg (50367 bytes, downloaded 1596 times)

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 tranny, but to no avail.

1. Replace ATF and change filter
2. Transmission Flush by the Nissan Dealer
3 TPS replacement
4. TCM replacement
5. Remove kick-down switch

Here is something that someone did to fix their tranny 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, 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

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

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)

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

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

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.

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.

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

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

240ROCKER

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.

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.

http://spaces.msn.com/members/...album

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

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.

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).

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.