2004 Dodge Ram P0157 O2 Sensor Code Persists Despite Straight-Pipe Modification

The P0157 diagnostic trouble code has not cleared even after using the OBD2 scanner to reset it. I understand this code relates to the oxygen sensor located in the exhaust system after the catalytic converter. However, my 2004 Dodge Ram was originally straight-piped when purchased—meaning there is no catalytic converter or downstream oxygen sensor. Given this modification, why does the P0157 code persist? Is there a safe way to disable or clear this code without replacing the entire exhaust system or installing a new oxygen sensor? Any advice on troubleshooting or bypassing the code would be greatly appreciated.