Engine Starts & DRB Displays "NO RESPONSE"

SYMPTOM
* ENGINE STARTS & DRB DISPLAYS "NO RESPONSE"

POSSIBLE CAUSES
- DRB adapter cable defective
- DRB defective
- PCM defective (no response)
- SCI receive circuit open
- SCI receive circuit shorted to ground
- SCI transmit circuit open
- SCI transmit circuit shorted to ground