QuestionQUESTION: Hello, I have been reading your Q & A's for 2 days now and I have learned quite a bit (for a girl)but still have some questions and hope you can help.
For the past 8 months or so I have been driving my fathers van, he pretty much gave it to me since he no longer drives. It has run perfectly up until a few days ago.
The Check Engine light came on at the same time the problem started. The transmission went into Limp mode all of the sudden, no warning signs whatsoever. I had my (only mechanical enough to get by# husband check the fluid and it was fine he said.
I then began reading, and decided to get the exact codes to give you and had my son borrow a diagnostic tool and get the codes for me.
They are as follows:
P0720 Output Speed Sensor Circuit Malfunction
P0734 Gear 4 ratio Incorr.
P0733 Gear 3 ratio Incorr.
P0134 02 Sensor Circuit No Activity
P0700 Trans Control System Malfunction
I am praying and hoping that this could be something simple. I had hoped that the speed sensor caused the limp mode which caused the 700, 733 & 734 codes and that if I replaced the speed sensor the world would be brighter the birds would sing again and it would all be okay #except for the 02 sensor which I am not stressing over.#
He replaced it #output speed sensor)last night and upon test drive it did not change anything. He then disconnected battery for a few to clear any residual codes related to trans and tried again but as luck would have it - no change again.
So I guess my questions are a few, Could he have installed this incorrectly or screwed anything up while doing so, (he is not an idiot but just isn't gifted in the car repair field# He made it sound like you couldn't really do it wrong, he took one off and put new one on.
Should I replace the input sensor too? Just to be sure?
So what we have done so far and in the order it was done.
Limp Mode begins
Check Fluid
Get Diag. Codes
Clear Diag Codes
Replace Speed Sensor
Test
Disconnect and reconnect battery
Test Drive
I pray that you have a simple answer and that it is something silly like you cant clear the codes until after fixing the problem and it is still an easy fix.
I havent told my dad about the problem yet, we have had a rough 3 years losing my mother and 2 of my brothers, my only job is to keep dad smiling which isnt an easy task sometimes. I know he will be very upset, and I try to keep him from getting upset these days, he is on a fixed income and I am disabled and also on limited funds. So I am trying to be optimistic and looking forward to your easy fix reply. #Crossing fingers) I am pressured for time - dad has a Dr. appointment in 4 days, hopefully I can fix this and not burden him with bad news.
Thanks for your time and I really appreciate what you do, there are still good people in the world.
P.S. I will be talking with you again soon as I have a 2001 Durango with 60,000 miles that also went into limp mode about 1 year ago and I have just parked it until I figured it out, hoping it has an easy fix too.
Anyway the Plymouth is a 1997 Grand Voyager Rallye 3.3 with 120,000 + mi on it bought used a few years ago.
Thanks again for your time.
Elizabeth
ANSWER: Hi Elizabeth,
The speed sensors and their circuits are not complicated. The possible reasons that the code did not go away and the limp condition didn't cease:
Did he replace the correct sensor, as there is an identically shaped input sensor located close the vertical rod that changes the gear setting. The output sensor is very close to the end of the transmission. The colors of the two wires on its plug are light green/white and dark blue/black.
The wires might not be patent between the plug and the transmission control module which is located on the upper edge of the right panel of the engine compartment, very close to the front. The wires that I listed are connected to pins 14 and 13, respectively of the multi pin plug at the module. So with an ohmmeter or continuity testor the wires could be individually tested once the plug is removed from the sensor. Also verify that light green/white wire shows a very high resistance between it and the dark blue/black wire, again when the plug is removed from the sensor.
Finally the sensor might not be screwed in all the way. The final degree of torque should be 20 foot-pounds which is very similar to that of a spark plug.
Of course the replacement sensor might be defective (if everything else is verified) or the plug may not be well-connected to the sensor.
I believe one of these possibilities will be found to be the cause.
Roland
PS Please 'rate' my answer. Thanks
---------- FOLLOW-UP ----------
QUESTION: Well I printed your answer and he went through the items 1 by 1 and nothing helped. Had son run ODBII again and he said that the only one that came up this time was the P0733 (Not sure what happened to the 02 sensor not appearing - we didn't touch that sensor, but maybe the car has to go a while before it gets enough information to rediagnose that condition) I broke down and told my father - he suggested I change the filter and Trans fluid. I ordered from the dealer the filter and fluid as well as sealer and today he changes the filter and fluid. Just took it for a drive and still have the same problem. No longer have access to ODBII reader, so did the dashboard lights test and came up with 12 45 55. I know 12 is start and 55 is end so what is 45? Also is there anything else you can think of that might help us fix this without the rebuild? Did not take back output sensor - but I guess it could be bad and we could try another. What are the chances of that though?
AnswerHi Elizabeth,
The persistence of the 733 and no longer showing the 720, on its face, would lead one to believe that there is an internal transmission problem that requires a rebuild. The only thing you might try would be to replace the solenoid pack/pressure switch assembly box which is done without having to remove the transmission. It might not repair the problem, but you could discuss that with an honest/experienced independent trans repair shop to see what they think of trying that approach first. In any case if the rebuild is necessary you might ask: if it would not be the case that a new solenoid/switch box would be needed to do the rebuild properly, so you wouldn't be wasting money on an unnecessary part. The box replacement is pretty straight forward in that model year as it is on the outside of the unit and held in place by only a few bolts. So trying that approach could avoid the total rebuild.
The OBD-I code 45 is not one that I have found yet, but it would only relate to the engine in any case.
Unless the 0720 returns soon I would give up on trying to replace the output speed sensor, particularly if you are sure that was the sensor that was replaced.
Roland
