“Since the tachometer pulses on many cars that have this problem with the power circuit to the HEP circuit, most will believe there is a HEP issue especially since the logic board will store a HEP code 54. Since the Power board supplies "8V" to the logic board AND HEP, if this voltage flops around it can cause a HEP signal error which the logic board reports as a code 54. Many turbo Dodge owners reporting HEP issues and swapping the HEP did not solve the problem. Interesting approx 30% of my SMECs have questionable 8V caps but good 5V and 12V caps.”

Miles Snow/chromguy has put together two videos on how to repair the HEP power circuit in the SMEC engine controller. 

Click here to open our SMEC HEP Power Circuit Repair FAQ (with link to Mile's YouTube videos)