Identifying Vehicle Communication Problems: Notes

Connect scan tool to Data Link Connector (DLC) to retrieve messages. If scan tool message is blank, see DRB BLANK SCREEN test. Disconnect scan tool. Ensure ground circuit has continuity at DLC terminal No. 4. Ensure 12 volts is present at DLC terminal No. 16. Try another scan tool and/or cable. See following bus fault messages list and proceed to appropriate DTC or fault message. If EEPROM CHECKSUM FAILURE or INTERNAL MODULE TESTS FAILURE message is received, replace BCM.

• ABS MESSAGE MISMATCH (ABS MESSAGE NOT RECEIVED; NO RESP CONTROLLER ANTILOCK BRAKE) 
• BATTERY POWER TO MODULE DISCONNECT (NO RESPONSE FROM BCM, (BAT PWR DISCON'D) BATTERY POWER TO MODULE) 
• EATX PRNDL MESSAGE TEST FAILED (NO RESPONSE FROM TCM) 
• EEPROM CHECKSUM FAILURE (INTERNAL MODULE TESTS FAILURE). Replace BCM.
• PCM MESSAGE NOT RECEIVED (NO RESPONSE FROM PCM) 
• BUS (+) & (-) OPEN (BUS (+) OPEN, BUS (-) OPEN, NO BUS BIAS) 
• BUS (+) & BUS (-) SHORTED TOGETHER 
• BUS BIAS LEVEL TOO HIGH (BUS BIAS LEVEL TOO LOW) 
• CCD SHORT TO 5 VOLTS 
• CCD SHORT TO BATTERY 
• CCD SHORT TO GROUND 
• DRB BLANK SCREEN 
• NO RESPONSE FROM ACM 
• NO RESPONSE FROM SKIM 
• NO RESPONSE INSTRUMENT CLUSTER 
• NO TERMINATION 
• NOT RECEIVING BUS MESSAGES PROPERLY