2002 2.4l Jeep Liberty, code P1281 went off, changed thermostat, but about 2 weeks later went off again. What else has the engine staying cold?
P1281 = Injection Control pressure out of range High.
Up in the 1000s range those codes are non-standard. Like you I am coming up with a P1281 indicating engine cold too long.
So…the other thing to check is the coolant temp sensor.