I have a 2011 with 3.6L V6.
I get the Service Traction warning and ESC Off message and never get them together with a CEL. I can almost 100% of the time generate the 2 messages by simply turning the steering wheel. A year ago I replaced the front wheel bearings believing that it might be the VSS (veh speed sensors) that also serve as the ABS sensors. Nope.
The 2 codes you got might be why they recommend the injector harness service. Is yours a 4-cylinder engine? If so, there have been TSBs about the harness near the coil packs needing to be moved and/or shielded plus a ground wire added for the coil packs. What happens is the EPS (electronic power steering) draws so much power that it causes the alternator to charge very strongly. The power passes by the coils and can induce a current in them, causing a misfire. Also, they can misfire and cause an induced current in the EPS that makes it twitch or do other funny stuff. My V6 has hydraulic PS so it doesn't have this issue.
Get them to provide more information on why they recommend the service. You, after all, are the one who is in control of your wallet. Don't go easily into the dark night of misguided advice on services that aren't needed or are completely wrong.
