Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
DTC Descriptor
DTC U1876 00: Drive Motor Control Module A Lost Communication With Engine Control Module (ECM)Diagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
ECM B+ | U1876*, U0100 in HPCM | U1876*, U0100 in HPCM | -- | -- |
ECM Ground | -- | U1876*, U0100 in HPCM | -- | -- |
ECM Wake Up Signal (circuit 5985) | U1876* in HPCM, U1814 in BCM | U1876*, U0100 in HPCM | -- | -- |
HSGMLAN + (circuit 2500) | 1* | U1876*, U0100 in HPCM | 1* | -- |
HSGMLAN - (circuit 2501) | 1* | U1876*, U0100 in HPCM | 1* | -- |
* Other modules/DTCs will set with this fault. 1. Scan tool does not communicate with high speed GMLAN device. | ||||
Circuit/System Description
Modules connected to the high and low speed GMLAN serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. The modules have prerecorded information about what messages are needed to be exchanged on the serial data circuits, for each virtual network. The messages are supervised and also, some periodic messages are used by the receiver module as an availability indication of the transmitter module. Each message contains the identification number of the transmitter module.
The serial data communication enable and the accessory wake up serial data circuits are energized by a specific module to activate another specific module when the ignition key is in ACC, ON or START. Only the modules using high speed GMLAN serial data are connected to the enable or wake up circuits. Refer to the schematics to determine which modules activate and are activated using the enable or wake up circuits.
Conditions for Running the DTC
| • | The system voltage is between 9-16 volts. |
| • | The vehicle power mode master requires serial data communication to occur fro this specific module. |
Conditions for Setting the DTC
A supervised periodic message that includes the transmitter module availability has not been received.
Action Taken When the DTC Sets
The modules is never signaled, therefore the specific subsystems will not function.
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 of 50, without a repeat of the malfunction. |
Circuit/System Verification
With a scan tool, ensure the following DTCs are not present in the modules as follows:
BCM
U1814
SDGM
U0100
| ⇒ | If any listed DTC is present, refer to Diagnostic Trouble Code (DTC) List - Vehicle to diagnose that DTC prior to this diagnostic. |
