Check Engine Light

[teddyu]

Received a check engine light on 2008 6.8L V-10 with 5 spd-auto in a F53 (motorhome chassis). I thought that a check engine light dealt primarily with emissions control devices and figured it was a sensor that went bad. The dealer troubleshooting indicated that a wiring hareness going to on near the transmission is bad and needs to be replaced. Does this sound right? What could this be? Wiring to the VSS? Something in the transmission? Your comments or thoughts would be appreciated.

[Franklin2]

It could be the harness, or a sensor, anything to do with the computer system on the truck. Any time you have a check engine light, it needs to be looked at, since it could be a serious problem, not just emissions. Some sensors and wiring, if they fail, will put the truck into a "limp home" mode, which can seriously affect your fuel mileage, and you know the cost of fuel these days.

More than likely they did get a sensor error on the tranny or the vss somewhere. It will give them a code for that sensor. If they replaced the sensor and it didn't fix it, then they would probably next look at the wiring. The computer looks at all the signals it receives, and the software knows the voltage levels that it expects to receive during certain situations. If this voltage level is way off, then it will store a code and turn the check engine light on.

If you want some more info, and double check their work, you might want to ride over to autozone or someplace else that will check the codes for free. Then you will have an idea of whats going on.