The problen is: The speedometer goes up and then down.

Speedometer cable needs replacing

The speedometer can fluctuate rapidly under normal driving conditions when the car's speed changes abruptly, but sometimes the needle can start swinging around the dial without any fluctuation in speed. If the hairspring comes loose or breaks, it can't hold the speed cup in place, and the result is a fluctuation in the dial. In electrical speedometers, if the circuit that counts the magnetic pulses fails, it can cause the speedometer read-out to vary from the actual speed and to shoot upward or downward without notice. If a speed sensor in the automatic transmission starts to malfunction, it can affect the speedometer and cause fluctuations. In these instances, either the speedometer or the sensor needs replacement.

hi ,the air bag light will need resetting ,have it reset by an auto shop who has a diagnostic machine to plug into it,some dont even charge for this service ,as for the speedo it could be a number of things that will need checking ,firstly fuses,then wiring leading from the speed sensor on the transmission up to the speedometer in the dash ,then have the speedometer removed and checked ,it has to be one of these ,THANK YOU FOR USING FIX YA

hi, sounds like the vehicle speed sensor mounted on the transmission is going bad or loosing signal. generally, honda speedometers work for life, i've only ever replaced one. now, this is a split year so it may have just a cable going to the transmission instead of an electronic sensor. if the cable is loose, this may also cause this issue. you should probably have a professional shop take a look as the speedometer cable/sensor is very buried in the back of the engine compartment under the air intake hose and behind the starter. also, if there is a check engine light on when the speedo stops working, this should be an easy diagnostic for a technician to do, it would likely be the speed sensor causing this engine light.

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.

This worked for me. Put the key in the ignition, but do not turn; press the trip reset button and hold until you see "SOF" you will then see the SOF and a number and an error code. Diagnostics will run and the needles on all the gauges will move during the procedure. The speedometer needle should be reset and working when done.

The bale may need replaced or sometimes if you go to a transmission shop they will sell you the gear wheel that goes inside your transmision where the cable plugs in .
Try that .
Good luck

I don't believe the problem is in the vehicle speed sensor. I suspect the problem may be the computer. The speed sensor is just a magnet inside the transmission with an induction coil outside to create an electrical signal every time the transmission output shaft turns. That signal goes to the computer and the computer tells the transmission when and how to shift and displays the speed on your electronic display. I would start by having a reputable transmission shop check out the transmission, then take it to a good mechanic to have him check the computer. It is a relatively expensive fix, but with only 70,000 miles on the Caddy, it should be worth it.

Replace the speed sensor on the trans that will cause exactly what you describe is happening.

First thing to do from a repair perspective is to hook up a scan tool to the OBD2 port.Go into the real time data stream and see if the vehicle computer is seeing a vehicle speed signal.If the computer is not seeing a speed signal,then it is likely a malfunctioning speed sensor on the transmission,and will have stored trouble codes with numbers and definitions.If the vehicle computer IS seeing a speed signal from the trans,then the speedometer gauge in the dash is malfunctioning.Either way,the vehicle computer has to be accessed with a scan tool,or code reader.Every diagnostic trouble code,has a diagnostic route.The diagnostic route is available through pay sources like All Data online.