QuestionQUESTION: Hi Roland, I wondered if you may be able to help. I do have some mechanical experience but not so much in tranmissions. We have a 96 Town & Country that has low miles and been real well taken care of. However driving on Friday it just literally stopped moving while driving down the street. It was towed, and is up on jack stands now. Engine runs fine. When not on the jack stands I put it in reverse, drive or neutral and it would not go anywhere (could not push either). Codes 720, 731 and 750 are showing. It also makes a whining noise when try to put it in drive. I erased codes and now that its on jack stands it will go into reverse for approximately 1 second and then shuts off and the wheels stop spinning. From what research we have done it seems input and output speed sensors may be the problem - what would your opinion be? I just got laid off from work and this couldnt have happened at a worse time for us.. so any input on where I should start would be much appreciated. Thanks for taking the time to read. Micah
ANSWER: Hi Micah
The 720 is an output speed sensor error. So that probably needs replacement. The 731 is a low/reverse solenoid error which would be an issue with that solenoid or accompanying pressure switch. These are located in the solenoid box on the front of the transmission and would be repairable or the wires connecting that solenoid to the trans controller verified for continuity. A defective l/r solenoid will prevent both 1st gear and reverse from operating and thus explain the no move. The 750 is for a gear ratio error for 1st gear which could very well be due to the problem with the low/reverse solenoid circuit.
So it would be good to replace the output speed sensor (simple remove plug connector after gently lifting tab, unscrew, make sure to transfer rubber seal to new sensor, screw in and tighten to about the same as a spark plug). Then tackle the low/reverse solenoid and fix that problem. Then see if that corrects the gear ration error which basically tells you that there is a mismatch between the input and output speed sensors in 1st gear and which may be corrected by fixing the first two.
Good luck on the project and let me know if you want the wiring connections, etc. for that solenoid. You would be helped by having some manual pages for opening and dealing with the solenoid box.
Roland
---------- FOLLOW-UP ----------
QUESTION: Thanks for all the info! Any kind of technical info / wiring connections etc would help - I folowed your advice and replaced the output sensor (did the input too). I dropped the trans pan, changed filter, fluid and reassembled. Tested and it behaves the same but 720 and 731 codes are gone. 750 remains. It is making a tapping sound that (sounds similar to a bad hydraluic lifter). I found some metal shards in the pan and on one of the sensors. I looked online and seems I can get solenoid pack but there are many part numbers and I am not sure which is the most current and updated one- do you happen to know? Thanks again - I really appreciate your help. Rock Auto gives me two options:
STANDARD MOTOR PRODUCTS Part # TCS52 {TRANSMISSION CONTROL SOLENOID}Shift Control Solenoid; with 4 Speed Trans.
and
DORMAN Part # 698100 {Original Equipment Solutions #4504570, 4504570AB, 5015646AB, 5015646AC, 5140429AA}
w/A604 4-Speed Auto Trans
I am guessing its the second one? Thanks again!
AnswerHi Micah,
Have you tried to see if it moves in any selector position setting?
Ideally it should not have failed entirely as you first described if it is only a solenoid switch problem. It should try to operate in limp-in mode which means only 2nd gear will work. The metal shards unfortunately are not a good sign. "Debris" in the pan indicates some significant breakdown of internal parts which typically causes there to be a need to remove and rebuild the trans. The whine and not the tapping sounds also are ominous. I am uncertain that you would be wise to purchase a solenoid pack given these symptoms.
You might try starting and operating it again a few times to see if the 731 code returns, which offers a glimmer of hope that it is only a solenoid issue. It has to detect that problem 6 times before it sets a code in the trans memory.
About the parts options, the first one is not one of the solenoids in the solenoid box but rather one that is mounted on the steering column of newer model vehicles to require that you have your foot on the brake in order to shift out of park or neutral. So if that Dorman is the only option, that would be the way to go if you decide to give it a try. If you want to look at the electrical resistance of the l/r solenoid and compare to that of the other 3 solenoids, just measure between pin 4 and pins 5,6,7,8, of the socket on the box. You could also jump 12V to pin 4, and then ground the other pins one at a time and listen for any differences in response; the l/r solenoid will be activated by ground pin 7. Pin 7 is wired to pin 20 at the transcontroller plug so you could verify that it has continuity. Then decide if you have support for a replacement.
Roland
