Good Day all,

Please i have an issue with my toyota camry 2011, i was driving two days ago and noticed the transmission was not changing properly from 1 to the next gear. the mechanic told me to do a scan which brought result of P0500 (Vehicle speed Sensor) and U0101 (Lost communication with TCM).

I want to know what is need to be done as my mechanic seems not to know anything about what is wrong with the car?

 

Does the speedometer work and trans shift normally?

There are 2 parts to this issue related to the two codes.

1) The cars computers monitor the various sensors for problems, one being the speed sensor. This sensor monitors the transmission shaft RPM and sends this info to the transmission computer called the TCM (Transmission Control Module). If the TCM finds there is a problem with sensor it sets the P0500 code.

2) The cars sensors including the speed sensor are connected to the computer by an electrical cable system which the computer also monitors. If the computer finds a problem with a cable connection (bad connection) it sets a code depending on where the problem connection may be. One code is U0101, meaning lost communication with the TCM. This is a computer that controls the transmission operation.

Code U0101 can also be set if a sensor (in this case the speed sensor) has problems which may lead the computer wrongly conclude the connecting cable is bad.
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Have the mechanic check the trans speed sensor for proper operation. Check the electrical cable plug connections at the speed sensor and TCM and cable between them for damage.

It happens that the electrical connections of the cable plug terminal pins have a poor electrical connection causing the "U" code. These terminal pins can be cleaned, adjusted, etc.

Think of having a poor TV picture from a cable TV system. The issue could be the cable TV system itself located off the property or the cable from the outside box to the TV. Sometimes jiggling the cable end at the TV fixes the issues due to a bad connection.

The car computer monitors both the speed sensor output (cable TV system) and cable but may not be able to tell the difference between between problem with one or the other. The mechanics job is determine which is the problem.

The Toyota dealer and better equipped auto shops have a scanner which will check the speed sensor output and electrical connections (cable) between sensors. If a cable has a connection problem the scanner will display that is not connected to the computer.

 

@ Super Moderator: the speedometer does not work, it just stands at zero and the trans shift jerks to select from 1 to 2 then the driving becomes smooth.

 

No speedo and trans shift problems point first to a bad speed sensor (P0500). Have the mechanic check the transmission speed sensor.

If the speed sensor is OK then check the wiring and plug connections between speed sensor and TCM (a possible cause of U0101) and the speedo and shift problems.

If the speed sensor is bad and replaced, the U0101 code should go away.

If the speed sensor is good and still have these codes, check the wiring.

Note this is the transmission speed sensor and NOT the speed sensors for the ABS. The trans speed sensor is located on the trans. The ABS sensors (4 total) are located at the cars wheels.