Heavy Equipment Repair Questions? Ask an Expert Now.
HiCustomer Welcome to JA. I am Buddy, and i will try and help you out.
What is the last 6 of your truck vin#?
Did both speedo and tach quit working at same time?
Has ecm been programmed or replaced recently?
The last 6 are K89565. The tach does not stop working at all. The only programming that I am aware of was shutting off the idle shutdown timer.
Thanks for the reply Jon. One more question, does the vehicle speed sensor have 4 wires or 2 wires and is there one or two sensors. If the vehicle speed sensor has 2 wires , the speedo head gets its information from the engine ecm. If it has 2 sensors or 4 wires it gets it information directly from the sensor.Also ohm out the sensor and let me know how many ohms resistance it has. Normally have around 800 to 1200 ohms. Let me know what you come up with and any other info you have and we will go from there.
It is a 4 wire pickup. I would have to get the truck back in here to check the ohms.
Thanks for the reply Jon. With the 4 wire sensor your speedo head will get its signal directly from the one side of the vss and the other side of the vss goes to the ecm.
The sensor is 4 wire but 2 wires plug in the harness & the other 2 have a cap in them. I assume the senor is an AC generator because if you drive the truck with a DVOM connected to sensor plug the voltage increases with speed. Any chance you would have a schematic.
Thanks for the info Jon. With this just using the 2 wires, it is going straight to your ecm. Wire numbers are 808 and 809. They go to the vehicle harness on the engine ecm to cavity 32 and 33. I am attaching 2 different diagrams for you . One is caterpillar wiring diagram and the other is freightliner diagram. With you not getting any vehicle speed with reader from the ecm while driving, i would bet your problem is from the vehicle speed sensor wiring to the ecm. I hope this info helps you out. If you have anymore questions, just ask.
THANKS SO MUCH FOR YOUR HELP. I AM GOING TO TRY TO GET THE TRUCK BACK IN HERE TOMORROW.