i have a Renault Megane 1.5 dci. I was on the motorway and my car went into limp mode, no warning lights came on dash or anything. I plugged in the obd reader and got a P0380 Glow plug/heater circuit A code. So I took it to mechanics and had all four glow plugs changed, however the car is still in limp mode and the same code shows. I did a proper diagnostic check from a mechanic and the same code P0380 still shows up. I don’t know what to do and ran out of ideas why this issue is occurring and why the car is in limp mode. Thank you.
The P0830 indicates a clutch pedal switch fault. The glowplugs aren't involved. Especially if the engine is already warm (it happened on the motorway, as you told).
I don't think that your mechanic is acting in a professional manner when he changes all your glowplugs without further diagnosis (as they are quite easy to check, even if installed)