The pyrometer can only be one of two things. Either the thermocouple and wire, (screwed into exhaust near turbocharger) or the gauge in the dash has gone bad. Most likely the thermocouple. Just get a new one, install it and good to go. It will only have two wires, one is red, the other yellow. Pay attention to how they are mounted to the gauge and reconnect the same way. These generate a small DC voltage to drive the meter movement and require no external power source other than for a backlight. They are known as a "Type K" thermocouple due to the temperature spectrum they are designed to operate within. The steering wheel typically comes off with the horn button twisting about 90 degrees to the left. Most you need to depress the horn button so I disconnect the batteries so as to not listen to the horn blow. You will then need to pull the nut on the steering shaft, install a puller and pull it free of the tapered shaft. I would probably have the alignment checked on the truck first however. Those wheels don't slip on the splines. Some are keyed, some are not so it is a possibility it was never installed with the proper orientation. Most times a non centered steering wheel is by incorrect setting of the toe alignment. This is the last adjustment in any front end alignment. If you've never had the service performed, it is worth the money for a thrust alignment to ensure all tracks as it should. Rob