U1016

DTC U1016

CIRCUIT DESCRIPTION
Each module connected to the class 2 serial data circuit monitors serial data communication during normal vehicle operation. Operating information and commands are exchanged among the modules. When a module receives a message for a critical operating parameter, the module records the identification number of the module which sent the message for state of health monitoring. Once a module learns another modules identification number, it will monitor the serial data for that modules node alive message. Each module that sends critical operating parameters is required to send a node alive message every two seconds. If no message is detected from a learned module for five seconds, DTC U1001-U1254 will set.

DTC DESCRIPTORS
This diagnostic procedure supports the following DTCs:
- DTC U1016 Lost Communications With Powertrain Control Module (PCM)
- DTC U1041 Lost Communications With Electronic Brake Control Module (EBCM)
- DTC U1064 Lost Communications With Body Control Module (BCM)
- DTC U1088 Lost Communications With Sensing and Diagnostic Module (SDM)
- DTC U1096 Lost Communications With Instrument Panel Cluster (IPC)
- DTC U1128 Lost Communications With Radio
- DTC U1151 Lost Communications With Onstar (VCIM)
- DTC U1176 Lost Communications With Remote Function Actuation (RCDLR)

CONDITIONS FOR RUNNING THE DTC
- Battery Voltage is 9-16 volts.
- DTCs U1300, U1301 or U1305 are not current.
- The vehicle power mode requires serial data communication to occur.

CONDITIONS FOR SETTING THE DTC
A node alive message has not been received from a module within the last 5 seconds after establishing class 2 serial data communication.

ACTION TAKEN WHEN THE DTC SETS
The module uses a default value for the missing parameter.

CONDITIONS FOR CLEARING THE DTC
- A current DTC clears when the ignition is cycled, and the malfunction is no longer present.
- A history DTC clears when the ignition has been cycled 100 times, without a repeat of the malfunction.

DIAGNOSTIC AIDS
- An intermittent open between a module and a star connector may cause this DTC to set.
- A poor connection at a module or a star connector may cause this DTC to set.
- An intermittent open in a star connector may cause this DTC to set.
- An open voltage or ground circuit to a module may cause this DTC to set.
- An internal module malfunction may cause this DTC to set.

When more than one loss of communication DTC is set in a single module or among multiple modules, diagnose the DTCs in the following order:
1. Current DTCs before history DTCs, except as specified in the diagnostic tables.
2. The DTC which is reported the most times.
3. From the lowest number DTC to the highest number DTC

TEST DESCRIPTION

Step 1:

Steps 2-3:

Steps 4-5:

Steps 6-8:

The number below refers to the step number on the diagnostic table.
6. The module which was not communicating on the class 2 serial data circuit may have set Loss of Communication DTCs for those modules that it was monitoring.