2008 Honda Civic EX with P0848 Code: D-Check Flashing and Third Gear Shifting Issue

My 2008 Honda Civic EX with a 1.8L engine is showing intermittent D-light flashing, which occurs only occasionally. The issue stops when I turn off the engine and restart it, remaining stable for several days afterward. A diagnostic scan reveals the P0848 code, indicating a problem with the transmission range sensor. While the car drives normally under most conditions, I notice a slight back-and-forth during third gear shifts. I've already had a mechanic inspect the connector and wiring—both are confirmed to be in good condition. The vehicle has manual shifting capability, and when used manually, there is no issue with shifting. This suggests the problem may lie with the sensor itself. Currently, I cannot replace the sensor due to budget constraints. My main concern: Is it safe to take this car on a 500 km road trip given these symptoms? The vehicle runs fine otherwise, but I want to ensure reliability during long drives.