Transmission problems check engine light is on and the speedometer won't work. We hooked it up to the machine and it kicked back something was wrong with the transmission. Could it be a sensor out? It will not shift out of first gear now.

This blazer forum will answer your questions. Hook up a scanner and see what the VSS and ABS sensors are reading.
https://blazerforum.com/forum/engine-transmission-35/abs-light-speedometer-not-working-not-shifting-50492/

i would unhook the cd player see if that helps. the wire for the dimmer might be ran wrong and that could be causing the problem.

The dash and running lights may be part of your headlight switch is bad. Check engine soon does not mea to change the oil. It means there is an issue with something having to do with the PCM and any of its related parts on the engine and/or transmission.
Need to have a code reader hooked up and see what code(s) are in the system.

You will need a speed sensor it at the tail of thhe transmission the very last one is speed output sensor or vss (vehicle speed sensor) NOT input sensor

Hi,
Your engine management and maybe even your transmission is controlled by the ECU. As such, many ECU units are fitted with a 'limp home mode'. When it detects that something semi-serious is wrong, it enters the limp mode, which means that the engine won't rev beyond a pre-programmed speed, you can't accelerate very fast, or you may indeed be speed-restricted to 40 mph or similar. The transmission may even stay in one or two gears. The alternative would be to either let you drive at regular speeds, with the danger of letting you trash your car or stopping you from going anywhere .
You should have a Check Engine light. Go to a major chain auto parts store and they should read the ‘code’ for free, then go to rdtiburon.com and ask what the code actually indicating or is really bad to your car. They will advise you what you ought to do.
Because you replaced the speed sensor and are still experiencing the problem, we suspect that you have a faulty speedometer cluster.
Please check this link and go through the article to have an indepth knowledge to your problem....

http://geekswithblogs.net/lorint/archive/2005/12/21/63765.aspx
Let us know if you want something else please accept the solution.
Thank You for contacting fixya.com

he told you to take it to a transmission specialist because that is where those sensors are located. The speed sensor is located in the transmission. It reads the speed by counting the number of teeth on a relucter wheel. (thats the simple explanation).
I sounds to me like there might be some debri in the transmission that could be affecting the reading.
The engine computer uses that information to control the engine and transmission. Without that information the transmission could go into limp home mode and or have erratic shiffting plus other problems.
I would really suggest you get it in for a test and evaluation asap. I do not consider this vehicle to be reliable or safe because the transmission could lockup and or otherwise fail.
As a side note, these minivans are notorious for having failing transmissions and most transmission shops find that the majority of their work is on this minivans. One of the reasons I have just kept my full size van.

Check your speed sensor. located on the tranny. AT tranny wont shift if you have a bad speed sensor.

If the speedometer is not working, try replacing the cable from the back of the speedometer to the engine or the transmission.