I unhooked my speeding because it was bouncing so much I was worried I may damage the gauge. I got a check engine light, pulled the codes. Code 42 makes sense no input from vehicle speed sensor, but I also got code 43 no starter signal to ecu. Truck starts and runs fine. I'm confused how unhooking speedo would cause this, although it could've already been stored, does code 43 illuminate CEL?

 

I have a code 42 as well , can't trace it down .my speedo does not work as well

 

Code 42 is speed sensor code, if u have a cable speedo it's unhooked or the cable is broken, if u don't have a cable it then the speed sensor on your transfer case may be bad.

 

just checked ,my speedo cable is broke at t-case.....

 

IF you have a cable speedometer, VSS1 is in the combometer. So if your speedometer is not working, VSS1 is generating no signal, and you will get code 42.

IF you have the electronic speedometer, VSS1 is in the back of the transfer case, and the signal from that sensor drives both the speedometer and the ECM.

 

without the VSS1 getting a signal will that throw off the ecm as to cause a stumble or power loss?

 

I don't think so, I've had mine unhooked for a few weeks now. I get a check engine light every time I drive it (although it's always off when I start the truck ) I have no loss of power or hesitation because of it though.

 

Keep in mind that your ecu recieves that speed signal from the dash. I dont' know what it does with that signal, but it uses it for something.