Expert: Roland Finston - 7/2/2011

Question
Car won't shift out of first. Have replaced output speed sensor, transmission module and throttle body positioning sensor.  Original scans showed P0731, P0733 and P0700.  Now it shows no voltage at input speed sensor.  Speed sensor is 2 wire sensor.  If cleared, car shifts good through all gears until it downshifts into first and then it will stay in first again.  Is there suppose to be voltage at input sensor with the key on?  Crand sensor and cam sensor have 8 volts on the orange and white wire.  Speed sensor has a white and yellow wire.  Speedo works.
Thanks.

Answer
Hi Steve,
There is no voltage applied to the input or output sensors, they generate their own signals without a polarizing external voltage source. It appears that all the sensors are working because the input and output sensors have codes 0715 and 0720. If the input sensor isn't too expensive though you might try replacing that, though it is a long shot.
A similar long shot is the solenoid/pressure switch assembly. That is located under the sound box cover (remove input sensor, then remove cover) then remove 3 vertical bolts that hold the assembly in position (install torque is 9 foot-pounds). The pack is usually replaced with a new/rebuilt unit...again consider the cost given it is a long shot. But at least on this transmission it is external and easily replaced compared to other models which require dropping the pan and removing the valve body to get to the assembly.
The most likely cause for speed ratio errors in both 1st and 3rd gear is worn clutches, seal rings, etc. that can only be repaied by removing and opening the transmission.
It is a judgement call as to whether to go directly for the r&r or try the sensor/assembly approach first. How many miles does the transmission have on it? These units can fail as early as 100k and seldom get to 200k.
Roland
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