Wacky speedo non shifting tranny 2002 grand caravan 6 cyl

dodge
caravan

#1

my speedo is bouncing back and forth and sometimes it dont move.with that happening the tranny usually dont shift from low gear,sometimes it will but today it hasnt so we parked it till i can get it to the shop and put it up on the lift so i can start investigating but i would like your opinion on if it may just be the input and out put sensors??your info would greatly be appreciated thank you


#2

Is the CEL (Check Engine Light) on? A bad Vehicle Speed Sensor (VSS) may cause this, but will definitely set the CEL.


#3

Definately get the computer scanned for codes. You will probably get a code for an output speed sensor along with gear ratio codes. This transmission is famous for speed sensor failures. What is happening with yours is the output speed sensor is most likely bad so the information it is relaying to the transmission computer is not consistant. This confuses the computer, the computer then puts the transmission in limp mode. This is why its not shifting. Take it to one of your local auto parts stores and have them scan the computer for codes. They usually scan for free. Post back here with the code/s and we will go from there. If it is indeed the output speed sensor, go buy BOTH the input and output speed sensors and change them.

transman


#4

today at work i used the mechanics scanner this is what i found for codes when the check engine light came on po731 (gear one ratio incorrect) po720(output speed sensor) po700(trans control system) so after work i cleaned the out put and input sensor it ran great on the way home appx 6 miles.i called a friend at local parts stor and they have both sensors in stock so tomorrow ill be replacing both of them plus the filter and fluid.should this correct my problem?? what is the trans control system code??will that be fine after i replace the sensors??one more question is how fluid will i need after replacing the filter.here in central ny the sensors are $19.37 a piece and the tranny filter kit is $11.56


#5

My 1999 Plymouth Voyager takes about 1 gallon of fluid when I drop the pan and replace the filter, every two years. Make sure to use ATF 4 fluid. I use the Mopar black RTV gasketing stuff in a tube. Other brands are fine as far as I know.


#6

Yea, change both sensors. Those sensors commonly go bad on these transmissions. If you do have any other issues with it it would be in the wiring because the connectors commonly give problems. The P-0700 (Trans control system) is a generic code telling you that the computer has picked up error codes in the TCM having to do with the transmission. The reason I recommended replacing BOTH input and output sensors is that first of all they both commonly fail. Second of all they both work together in the shifting of the transmission. The transmission computer take the readings from both sensors, the turbine shaft speed and the output shaft speed, it then converts both readings into a gear ratio. When the computer sees a gear ratio which is programmed into the computer it will shift the transmission. If it does not see one of the pre programmed gear ratios, it will throw an error code for that gear and place the trans into limp mode. With yours, the computer was detecting erratic readings coming from the output speed sensor, first gear never reached a pre programmed ratio so both of those codes appeared. The speedo receives its info from the output speed sensor so thats how the speedo became involved. And the third reason I recommended changing both sensors is that they are so cheap anyways. Dont worry about mixing them up when you change them because they have different threads on them, one is coarse thread and the other is fine thread.

transman


#7

after work today i changed both sensors and decided not to do the filter and fluid only because it looked good and didnt smell burnt.on the way home the van ran great and shifted great.thanks all and transman you have been a great help thank you and take care


#8

Glad to help, thanks for the follow up, good to see you on the road again.

transman


#9

well i thought it was fixed now today the damn piece of junk started in doing the same thing and it pop the same freaking 3 codes PO731 720 & 700 so now im stumped and ticked off any sugestions would greatly appreciated


#10

When you read the codes, did you use a scanner or a code reader?? If you have access to a scanner, use it because you are going to need to monitor some live data. Monitor your input and output readings while you drive. In 3rd gear both readings should be the same. Also while stopped, monitor your output reading while wiggling the output sensor connector. See if you get any erratic readings.

transman


#11

I have the same problem on my 2001 Town and Country. I did the same as you have only to find out there was a break in the wiring on the sensor closest the tire. Dealer fixed and I had to re-fix a year later…Now after another year I am getting it intermittently. When dealer fixed they soldered the damn thing. I used crimp ons and electrical tape.


#12

I need your help please! We have very similar issues on our GMC Terrain codes 700,716 n 717
My wife is going into surgery, I cant afford a $350 Trans control module, especially if it’s the other sensors or bad wires etc you mentioned. The car is running but in limp mode and shifting very poorly (automatic)
Thank you


#13

We ALL wish that transman would respond to your posting, but–unfortunately–he has been absent from this forum for at least a couple of years, so it isn’t likely that he will give you a response.

Transmission diagnosis via cyberspace is never an exact science, and regardless of your current finances, I don’t think that you have any alternative but to take your vehicle to an INDEPENDENT trans shop for examination and diagnosis. Whatever you do, do NOT go to a chain-run trans shop like Lee Myles, Cottman, Mr. Transmission, or–GOD forbid–AAMCO.


#14

I seem to remember another posting you made for this same issue. Since the P0716 code refers to a circuit problem for that sensor you need to check the wiring to it and make sure the proper voltages are present at the sensor. Power most likely isn’t getting to the sensor.


#15

Hey Cougar, I hope replying to you directly is ok, not trying to circumvent a post-chain. My mechanic felt the car was behaving like it was low on fluid or the filter was clogged (I concur), I would tell you it has no dipstick and is a sealed system. It’s only serviced like after 75K or problems exist. He did find it was a quart low, but he could not pull the filter as it required a special tool he didnt have. Now things get messy Cougar. I tell the shop I want the filter changed before we deal with sensors and he tells me the tranny has to be pulled to change the filter (I’m immediately suspect). I call the GMC dealer and they charge $199 to change the filter, $1050 to replace the “Input Speed Sensor” because the tranny does have to be dropped to replace that sensor ($985 labor). This means my new tranny shop owner friend bold-face lied to me. GMC would not charge only $199 for filter replacement if they had to drop the tranny. I assume it’s time to have my car towed elsewhere? Thank you


#16

Please stop having your problem in so many different threads .


#17

I’m sorry to bother you, I didn’t realize I’d done this… I was simply panicking, I will gladly delete anything you ask.


#18

Do you think resorting to a dealer visit would be wise? It does appear that this model has a more complex system since it doesn’t even have a dipstick to check fluid levels. The dealer quoted me $199 to change the filter and the tranny shop claims they have to pull the entire tranny just to change the filter. Someone’s not being straight with us.


#19

If the transmission control unit doesn’t get the proper sensor input data then the controller can make it seem there is a problem with the transmission, but really the problem is due to the faulty sensor data. The fault code you gave tells me that there is something wrong with the sensor circuit wiring and the sensor itself is most likely fine. If it was my vehicle I would make sure that the wiring to that sensor was completely checked out before doing anything further. I suspect a problem will be found with the wiring and after that is fixed no more codes will appear and things will run normally, but I could be wrong.


#20

Hey Cougar, thanks once again, see my posts with George San Jose, the great news is it wasn’t mechanical (no rebuild) so the tranny shop I towed it to was full of it. Let this be a lesson to anyone with tranny-related codes. When he told me he could do it for just $3,000 (but there might be a $700 part needed he could get me for just $375) I couldn’t tow it fast enough. I hear you, my guys dropped the tranny case and replaced the input speed sensor (I had it anyway), found out the dealer charges $500 to do the tranny filter…$500 for a tranny filter! Anyway, I’ll have them check the wiring harnesses, hopefully it’s not too hard to find which goes to the PCM, my guys aren’t exactly the type that read shop manuals, just good, honest mechanics that do free stuff for me all the time, never charge me for OBD scans, fluid etc I try to do the tech legwork with you fine gentlemen. Hopefully they can still run a scan after the speed sensor replacement but before they close up the tranny. Thanks for all your help again