Part number for speedometer sensor

[BazzaNova]

Hi, I have a Noah Townace/liteace camper van, it's a 1997 import, diesel automatic and the speedometer has suddenly started to become intermittent. When the speedometer reads zero, the odometer is also not working, however when the speedometer does work, so does the odometer. I've googled it and most posts I've read seem to suggest the sensor, I don't think I have a cable drive but could be wrong. I'm hoping someone out there may know? Which ever it is I'd need a part number so I can order a new part. As it's an import and an old model, my local Toyota dealer can't help, as they can't get the manual on their computers, I've had this problem with them for other parts I've needed. Can anyone help? 

[Xanadu_999]

Toyota Lite Ace Noah