This a concise summary of the key AT-commands to program the ELM237 for OBD diagnostic with focus on the KWP 2000 protocol. If you follow these steps you save yourself lots of time and errors. -This is a concise summary of the key AT-commands to program the ELM237 for OBD diagnostic with focus on the KWP 2000 protocol. If you follow these steps you save yourself lots of time and errors.