First off we should address the Diagnostic codes you have provided. Code P0700 ETAX (Transmission Control Module - TCM)Controller DTC Present.; This means that the Powertrain Control Module (PCM) has detected a Diagnostic Code in the TCM. P0731 - GEAR RATIO ERROR IN 1ST, This code is set if the ratio of the input RPM to the output RPM does not match the given gear ratio. P0720- OUTPUT SPEED SENSOR ERROR; This code is commonly set because of the Output Speed sensor failure. The Chrysler Part number for the sensor is 4800879 and costs about $25.00. Labor time to replace is about 30 minutes.
Visitoron Jul 11, 2011
I have a Town and Country 2001 with 3.3L. Same codes 700, 720, and 731. My issue started with the speedo jumping around and transmission slipping at takeoff. Replaced output and input speed sensors. No help. Checked and cleaned wiring and connectors and replaced battery. Alternator tested fine. I did the speedo reset a few times when the needle went clear around and stuck: Key on, then to accessory, hold trip reset for about 5 seconds and the speedometer goes into test mode and resets itself. Drove the vehicle a few more times. Soon the speedo began to always hover around 18mph in neutral and drive when completely stopped. After takeoff speedo would return to normal and no problems until coming to a COMPLETE STOP. Trans would "off and on" jump gears at takeoff, since it did not know what gear it should be in. Stalled a few times. Went into limp mode a few times until I turned off and restarted. Chrysler Parts Department guru of 35 years had supplied a tech with a 2nd output speed sensor for another client with same issue. That still did not fix it. The tech found the Trans Silonoid Pack was leaking into the electrical connector and that was the problem. I had found trans fluid in mine, so I bought a new TSP and installed. No luck, but it did need replaced since it was leaking and a potential issue. (Had also recently had a fluid flush, which many times kills the TSP I hear) As the problem had gotten worse I noticed my alternator was making a high pitched sound. Even though it tested good, lights never dimmed, and battery never weakened, I REPLACED THE ALTERNATOR AND THIS COMPLETELY SOLVED THE ISSUE!