Condition Not Present Diagnosis

Sometimes conditions can be duplicated by carefully warming data line components using a heat gun and/or lightly tapping them. If condition cannot be duplicated on vehicle during diagnosis, use following procedure:

1. Ensure grounds on fender near battery are clean and tight. Ensure star washers are present on studs and studs are free of corrosion.
2. Check BCM EPROM, EEPROM, ECM CAL-PAK and PROM or MEM-CAL assembly for proper insertion into their respective sockets. Inspect components for bent or damaged legs.
3. Ensure both BCM and ECM have correct PROMs for vehicle model year.
4. If source of intermittent problem has not been found and intermittent condition persists, verify good connections at following components.
   • ECC Head
   • BCM
   • Programmer
   • ECM
   • BCM EPROM
   • IPC
   • ECM CAL-PAK And PROM.
   • BCM EEPROM

If connections are okay, replace components individually, checking for reoccurrence of intermittent condition after each component replacement. Follow listed order; it represents most likely to least likely cause of a multiple communications code condition.

Fig 1: Serial Data Ckt Multiple Intermittent Codes CRT/DID

Courtesy of GENERAL MOTORS CORP.