Data Link Communications Diagnosis

DTC U1016 Loss Of Communications With PCM:

CIRCUIT DESCRIPTION
Class 2 control modules receive a state of health message from the Powertrain Control Module (PCM) through the Class 2 serial data link.

CONDITIONS FOR SETTING THE DTC
Class 2 control modules do not receive a state of health message from the PCM after receiving other messages from the PCM.

ACTION TAKEN WHEN THE DTC SETS
^ Class 2 control modules store DTC U1016 in memory.
^ The SERVICE VEHICLE SOON indicator lamp turns on.

CONDITIONS FOR CLEARING THE DTC
^ DTC U1016 changes the status from current to history when class 2 control modules detect a state of health message from the PCM.
^ Using a scan tool.

DIAGNOSTIC AIDS
^ The following conditions may cause an intermittent malfunction to occur:
^ An intermittent open, short to ground, or short to B+ in circuit 1049.
^ Poor connections at the PCM.
^ Control modules may store DTC U1016 if certain diagnostics are performed between the Powertrain Control Module (PCM) and the Data Link Connector (DLC).
^ DTC P1626 will set in the Powertrain Control Module (PCM) when the ignition switch is on with the Body Control Module (BCM) disconnected. When BCM diagnostics and repairs are completed, refer to Computer and Control Systems for additional information on PCM related DTCs. Computers and Control Systems

TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic table.
1. This step checks for an open in the Splice Pack SP205.
2. This step checks for a short to ground in circuit 1049.
3. This step checks for a short to B+ in circuit 1049.
4. This step checks for an open in circuit 1049.