This is a Hemi. I have a code P2181 and vehicle sounds like engine is revving very high, but tachometer remains steady

The code is for Cooling system performance. Start by checking your coolant level. There is also a Technical Bulletin out for reflashing the PCM if this code persists. We would be able to help with diagnostics and reflashing if necessary. You can call us at 217-469-2018 for further assistance if needed.