This might sound crazy or I might be the only person in the world that has this issue.. I have no idea.

Last night I finally finished wiring up my engine harness. So I wanted to power it up. (Starter not connected yet, wires were not touching anything)

The car turned on and had power however MPH was set at 105 mph and my mileage was going up as if I was driving 100 MPH lol.

What would cause this? I turned the car off and disconnected the transmission harness from the main harness and it was still doing this. (Maybe thinking I had a faulty Speed Sensor)

Any ideas?

 

according to this pinout http://www.roadraceengineering.com/e...-ecuwiring.htm pin 86 is the vehicle speed sensor pin, you could try pulling that pin from the harness, if its still does it, could be a fried ecu, if it stops then you will want to trace out that pin and see whats mixed up.

 

Think that would be the sole cause of it though? It's not maybe a bad ground?

Anyone local and want to test my ECU for me?

 

there are many things it could be, you need to start narrowing down the search. Im not saying it would for sure be the ecu if it doesn't stop but you can narrow your search to between the ecu and the cluster. You should definitely check all your grounds.

 

You saying your speedo is constantly at 100 mph? Unplug the alt and turn on see if that helps.

 

Correct. 105 mph to be exact. So unplug my alternator wire and see if it fixes it? And if it does what does that mean?

 

Sometimes when your regulator is busted your tachometer and speedo go nuts. It's just a check I do when a customer describes weird stuff happening.

If that doesn't help. I believe these are three wire speed sensors. (Power, ground and signal), check for good power, signal and ground with sensor plugged in. You should only need a test light and a multimeter. Unless you had to hard wire the sensor it should have factory connections. I think the ecu gives it 5v and the sensor pulls it down with speed so if the signal is fixed low could be v sorted to ground.

 

Break out that fsm and pull up the wire diagram. The vss sensor gets power and ground from the cab.

i just redid my whole harness and it was the only sensor that was routed that way. So if you connected it to an engine +12 and ground that could be part of your issues.

I will see if I can track down my notes.