Originally Posted by
blindsquirrel
What harness? Reworked stock or aftermarket?
One thing I notice is, 'P0606' looks very similar to 'P060D', and as it happens both are on the same page in the service manual. P060D is 'Control Module Accelerator Pedal Position (APP) System Performance'. I have seen diagnostic software misname a DTC - P0116 reported as being P0115, for example. There is no such code as P0115.
What do you know about the history of the ECM? Have you ever flashed it yourself, if so using what tools, and what did you do? Did it come from a real known-running '08 Trailblazer? Any chance it's been monkeyed with, like had the OS changed using something other than a Tech2/MDI+SPS?
If you have any doubts about the above, I'd try flashing it with a stock calibration using real proper tools (not HP Tuners). If nothing changes it's time to try a different ECM (as long as it's from the same year/platform you can just plug it in and run the scan without licensing anything, see if the TPS behavior is notably different).