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 U1881 Electro-Hydraulic Power Steering (EHPS) Module Lost Communication With Energy Storage Control Module (ESCM) |
| • | DTC U1882 Energy Storage Control Module (ESCM) Lost Communication With Electro-Hydraulic Power Steering (EHPS) Module |
| • | DTC U1883 Hybrid Control Module (HCM) Lost Communication With Driver Door Module (DDM) |
| • | DTC U1884 Hybrid Control Module (HCM) Lost Communication With Passenger Door Module (PDM) |
| • | DTC U1885 Energy Storage Control Module (ESCM) Lost Communication With Hybrid Control Module (HCM) |
| • | DTC U1886 Energy Storage Control Module (ESCM) Lost Communication With Powertrain Control Module (PCM) |
| • | DTC U1887 Energy Storage Control Module (ESCM) Lost Communication With Starter/Generator Control Module (SGCM) |
| • | DTC U1888 Hybrid Control Module (HCM) Lost Communication With Energy Storage Control Module (ESCM) |
| • | DTC U1889 Hybrid Control Module (HCM) Lost Communication With Body Control Module (BCM) |
| • | DTC U1890 Hybrid Control Module (HCM) Lost Communication With HVAC Control Module |
| • | DTC U1891 Hybrid Control Module (HCM) Lost Communication With Instrument Panel Cluster (IPC) |
| • | DTC U1892 Hybrid Control Module (HCM) Lost Communication With Electro-Hydraulic Power Steering (EHPS) Module |
| • | DTC U1893 Hybrid Control Module (HCM) Lost Communication With Powertrain Control Module (PCM) |
| • | DTC U1894 Hybrid Control Module (HCM) Lost Communication With Starter/Generator Control Module (SGCM) |
| • | DTC U1895 Electro-Hydraulic Power Steering (EHPS) Module Lost Communication With Powertrain Control Module (PCM) |
| • | DTC U1896 Electro-Hydraulic Power Steering (EHPS) Module Lost Communication With Starter/Generator Control Module (SGCM) |
| • | DTC U1897 Starter/Generator Control Module (SGCM) Lost Communication With Energy Storage Control Module (ESCM) |
| • | DTC U1898 Starter/Generator Control Module (SGCM) Lost Communication With Hybrid Control Module (HCM) |
| • | DTC U1899 Starter/Generator Control Module (SGCM) Lost Communication With Powertrain Control Module (PCM) |
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:
• For DTC U1892, ensure all power and ground circuits to the electric-hydraulic power steering (EHPS) module including the motor are tested. A loss of voltage or ground to the EHPS hydraulic motor as well as to the module may cause a loss of
communication. • 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
The number below refers to the step number on the diagnostic table.
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The hydraulic motor EHPS 42 V battery voltage circuit includes a 125 A EHPS fuse inline, which is part of the 42-volt harness, below the starter/generator control module next to C121.
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The module which was not communicating may have set Loss of Communication DTCs for those modules that it was monitoring.
Step | Action | Yes | No | ||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Data Communication Schematics Connector End View Reference: Master Electrical Component List and Inline Harness Connector End Views | |||||||||||||||||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |||||||||||||||||||||
2 | Was any DTC in the range U1001-U1254 recorded? | Go to DTC U1001-U1254 | Go to Step 3 | ||||||||||||||||||||
3 | Was any DTC in the range U0100-U0299 recorded? | Go to DTC U0100-U0299 | Go to Step 4 | ||||||||||||||||||||
|
Important:
Test the following circuits of the module that is not communicating for an open or a short to ground:
Refer to the following:
Did you find and correct the condition? | Go to Step 9 | Go to Step 5 | |||||||||||||||||||||
5 |
Important: A loss of ground to the electric-hydraulic power steering (EHPS) hydraulic motor as well as to the module may cause a loss of communication.
Refer to the following:
Did you find and correct the condition? | Go to Step 9 | Go to Step 6 | ||||||||||||||||||||
6 | Test the class 2 or/and high speed GMLAN serial data circuits of the module that is not communicating for an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 9 | Go to Step 7 | ||||||||||||||||||||
7 | Inspect the harness connectors of the module that is not communicating for poor connections and terminal tension at the following circuits:
Refer to the following:
Did you find and correct the condition? | Go to Step 9 | Go to Step 8 | ||||||||||||||||||||
8 | Replace the module that is not communicating. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 9 | -- | ||||||||||||||||||||
Does the scan tool display any DTCs which do not begin with a "U"? | Go to Step 10 | ||||||||||||||||||||||
10 | Select the Display DTCs function for the modules which had the Loss of Communications DTC set. Does the scan tool display any DTCs which do not begin with a "U"? | Go to Step 11 | |||||||||||||||||||||
11 |
Did you complete the action? | System OK | -- | ||||||||||||||||||||
