U1898

DTC U1898

CIRCUIT DESCRIPTION
Modules connected to the class 2 and high speed GMLAN serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. All DTCs in this range are reported on class 2 link to the scan tool by powertrain control module (PCM) even if they may be set by different modules.

DTC DESCRIPTORS
This diagnostic procedure supports the following DTCs:
- DTC U1898 Starter/Generator Control Module (SGCM) Lost Communication With Hybrid Control Module (HCM)

CONDITIONS FOR RUNNING THE DTC
Voltage supplied to the module is in the normal operating voltage range of 9-16 volts.

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

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 malfunction is no longer present.
- A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

DIAGNOSTIC AIDS

IMPORTANT: DTCs U1883 and U1884 can be set inadvertently, when braking during the trailer towing. If only these codes are set as history only, clear the codes.

- An intermittent open between a module and a star connector may cause this DTC to set.
- An intermittent open on high speed GMLAN 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.

TEST DESCRIPTION

Steps 1-8:

Steps 9-11:

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