QuestionQUESTION: I have 1999 Dodge stratus that has a code P0731 and P0700 also the speedometer stopped working when the check engine light came on. Wondering what would cause this. would it be the ransmission control module?
Dave
ANSWER: Hi Dave,
The loss of the speedometer most likely means "output speed sensor" has gone bad. That sensor is located on the side of the trans that faces the front of the car. There are two speed sensors that look identically, one on either side of the vertical shift rod. The output sensor is the one near the far end of the transmission. It has a plug with a tab on the side which if lifted gently will allow you to remove plug. The sensor then unscrews and a replacement can be screwed in and tightened to about 20 foot-pounds which is about the same torque as as spark plug. You may have to remove some overlying parts to get good access to see/remove the sensor or possibly go at from underneath. In any case its two wires are colored dark blue/brown and light green/violet.
You can shop around for the part as the price ranges between about $25 and 80, so do some comparison shopping.
The 0700 code says there is a transcode in the memory, and the 0731 says that code is about there being a discrepency between the output speed and the input (torques converter) speed sensors that would be expect when 1st gear is used. While that could also mean some internal issue with the clutches (which would be an expensive repair), because the speedo also stopped that means the sensor is bad and that is also a possible cause of the 0731 code. So pursue that repair first and keep your fingers crossed.
Roland
---------- FOLLOW-UP ----------
QUESTION: I haven't done any repair yet. Did notice that when driving it doesn't shift out of the lowest gear. Are there any other censors that may cause this or is it an internal problem with the transmission
AnswerHi Dave,
There could also be a similar problem with the input speed sensor, but because the speedo went out recently I would believe that it is the output sensor. It could be a problem with the transmission controller, or the wiring from the sensor to the controller.
The sensor and the wiring are something you can change/check yourself. The trans controller would show a different code most likely. The last possibility is an internal mechanical problem with the transmission but that is a $2,000 job. So that is why I would suggest you check the wires to the output sensor to verify they aren't damaged, and then replace the sensor proper. If the speedo is working again, then disconnect the battery to clear the fault codes and cancel the limp mode, reconnect and then try driving it and see if the speedo works and the trans shifts. If not, then change the speed sensor; if so, then wait until the speedo quits again, and I suspect it will go into limp again. Then re-read the codes to verify still 0731 (or 0720) and change the speedo sensor.
Roland
