Speed sensor error code speed ometer not working after car heats up o/d light flashes on start up whats going on?

Sure is. Replace it and things should go back to normal.

What sensor is new , vehicle speed sensor (vss) ? That's not how it works ! The speed sensor is an input to the engine computer ,from the engine computer it is sent to the instrument cluster over class 2 or UART serial data bus which ever this has ! The gauge it self is bad or actually it's the stepper motor that is bad ! How to Fix GM Speedometer Instrument Lighting

Get the manual and check what the flash codes are??
What vehicle is it? What engine? What year?

Wait a second and keep your eye on the check engine light. You should see it start to light up in a series of flashes.

The light is blinking in a simple code of long and short. Long blinks mean "10" and short blinks mean "1".

The light was blinking once for a long time, and then twice for a short time. 10, 1 and 1 is error code 12. Code 12 indicates a problem with my EGR system. This is the system that sends some of the engine's exhaust into the cylinder to cool the combustion process and keep temps in the cylinders down. Having a broken EGR is relatively common on a high mileage car (I have 180,000 miles on mine) and it's a pretty easy fix. I was worried that I might have to pull over to the side of the road when I saw the light or get it to a mechanic ASAP, but now I know that it's not life threatening to the car and that it's OK if I get it looked at the next time I am at my mechanic.

You can find a list of error codes for the make and model of your car online by doing a simple search. The ones for Honda are included below.

Honda Check Engine Light Error Codes

0 ECU
1 Oxygen Sensor
3 Map Sensor
5 Map Sensor
6 Crank Angle
7 Throttle Angle
8 TDC Position
9 No. 1 Cylinder Position
10 Intake Air Temperature
12 Exhaust Gas Reiculation (EGR) System
13 Atmospheric Pressure
14 Electronic Air Control
15 Ignition Output Signal
16 Fuel Injector
17 Vehicle Speed Sensor
20 Electronic Load Detector
22 Vtec System Malfunction
23 Knock Sensor
41 o2 Sensor
43 Fuel Supply System
45 System Too Rich or Too Lean
48 Primary Heated o2 Sensor
54 Crankshaft Speed Fluctuation Sensor
61 Primary o2 Sensor Circuit
63 Secondary o2 Sensor Circuit
67 Catalyst Sytem
70 Automatic Transaxle
71-74 Random Misfire
80 Exhaust Gas Recirculation
86 Engine Coolant Temperature Circuit
90 Evaporative Emission Control System Leak Detected
91 Fuel Tank Pressure Circuit
92 Evaporative Emission Control System Insufficient

I'd try changing the speed sensor most likely mounted on the outside of the transaxle which is wired to your motor as a fail safe causing it not to start so replace the speed sensor which also could throw a transaxle code then disconnect your battery for 30 min to reset your engine light then reconnect battery and try starting

Could be the speed sensor in the transaxle.

IF SPEEDODMETER BY ITSELF NOT WORKING THE VECHICLE SPEED SENSOR FAULTY.CHECK VECHICLE SPEED SENSOR MAKE SURE ELECTRICAL CONECTOR NOT LOOSE OR DISCONNECTED. IF YOUR INSTRUMENT GAUGES LIGHT NOT WORKING LOOK FOR BLOWED FUSE.

SPEED SENSOR WILL CAUSE THIS BEHAVIOR

it sounds like your vehicle speed sensor has failed. Go to autozone and ask for a free computer scan to get the fault code.

Do any ights on the dash come on or flash?

VECHICLE SPEED SENSOR.COULD BE THE PROBLEM.SCAN IT TO CHECK IT OUT.

The fuse panel should be below the steering wheel to the left. A blown fuse would explain why the electronic speedometer isn't working, but a blown fuse wouldn't explain the OD light. If the speedometer starts to work after replacing the fuse, but reads erratically, you might want to check the vehicle speed sensor.