I had a 2014 Caprice police special with a 6.0 come in today. The vehicle was ready for delivery but the MIL was on. Scanning with GDS2 showed a p0455 set current in the ECM. Checking data, there was no PID for fuel tank pressure available. Proceeding to EVAP Output Control, there was only an option to control the purge solenoid but no control of the EVAP vent solenoid and no purge/seal procedure available.

A quick visual showed a tight fuel cap and all visible lines attached firmly. The EVAP cannister and vent valve are in a similar position to the Camaro but less accessible if that can be believed. Since I can't command the vent solenoid closed, I can't test the EVAP system with smoke or nitrogen. I can't read the fuel tank pressure sensor so I don't know if there really is an EVAP leak present. Now what?

The version of GDS2 was the most current available. Since GDS2 reads the VIN, it automatically enters the type of vehicle that you're working on. How to fool it? If you go to the first diagnostic screen and remove the VIN and put number 1 in the block and hit enter, you will be directed to another screen that lets you manually enter the vehicle type. I entered the vehicle as a 2014 Silverado with a 6.0 and my missing PID's and functions appeared. Normal diagnostics then showed the problem to be a failed vent valve that would not close.

James from Florida