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 U189A 00: DC to DC Converter Control Module A Lost Communication With Hybrid Powertrain Control ModuleDiagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
PTLAN + 2 circuits at PIM | U0074* | U189A* | U0074* | -- |
PTLAN - 2 circuits at PIM | U0074* | U189A* | U0074* | -- |
Wake Up Signal circuit 968 | B137A* in SDGM | U189A* ** | 1 | -- |
Wake Up Signal circuit 932 | B137B* | U182A* | U189A* | -- |
Wake Up Signal Circuit 5985 | U1814* in BCM | U1812* in HPCM | U209A* in SDGM | -- |
* Other modules/DTCs will set with this fault. ** Open at SDGM or BECM will set DTC U1812 in HPCM. Open at PIM will set DTC U189A in the HPCM. 1. Parasitic drain on battery, and may set DTC U1875, U1876, U1878, U1879 as history in the HPCM with the key ON, or as current with the key OFF. | ||||
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 SDGM energizes the wake up signal to activate the accessory DC power control module (APM) and another wake up signal to activate the hybrid powertrain control module (HPCM) which is inside the drive motor power inverter module (PIM). The HPCM reports all DTC for the APM, therefore DTC U189A cannot be reported with the HPCM is inoperative.
Conditions for Running the DTC
| • | The system voltage is between 9-16 volts. |
| • | The vehicle power mode master requires serial data communication to occur. |
Conditions for Setting the DTC
| • | The HPCM does not receive voltage from the SDGM on the wake up signal circuit. |
| • | The wake up circuit between the SDGM and the APM is shorted to voltage. |
| • | Any of the 4 PTLAN circuits connected to the HPCM are open. |
Action Taken When the DTC Sets
The modules is never signaled, therefore the specific subsystems may not function. Depending on the fault, the MIL, battery indicator may illuminate and several DIC messages be present.
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. |
Diagnostic Aids
| • | When testing circuits to the SDGM access can be accomplished by removing the instrument panel center trim panel. Note that this procedure does not allow removal of the SDGM, only access to the connector. Refer to Instrument Panel Center Trim Panel Replacement. |
| • | Circuits to the HPCM are diagnosed only to the PIM connector because the HPCM is replaced as part of the PIM. |
| • | Different DTCs may set in different modules along with this DTC depending on where the fault occurs and the vehicle operating conditions when the fault occurs. |
Reference Information
Schematic Reference
Connector End View Reference
Description and Operation
Data Link Communications Description and Operation
Electrical Information Reference
Circuit/System Verification
With a scan tool, ensure the following DTCs are not present in the modules as follows:
| • | BCM - U1814 |
| • | HPCM - U1812 |
| • | SDGM - B137A or U209A |
| ⇒ | If any listed DTC is present, refer to Diagnostic Trouble Code (DTC) List - Vehicle to diagnose that DTC prior to this diagnostic. |
Circuit/System Testing
- Ignition OFF, disconnect harness connector X1 of the APM.
- Test for less than 0.5 volts between the wake up signal circuit terminal 3 and ground.
- Disconnect harness connector X1 of the PIM.
- Test for B+ between the wake up signal circuit terminal 19 and ground.
- Test for less than 1.0 ohm between the APM and the PIM on the following circuit terminals.
- Ignition OFF, disconnect harness connector X3 of the engine control module (ECM).
- Test for less than 1.0 ohm between the APM and the ECM on the following circuit terminals.
| ⇒ | If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the SDGM. |
| ⇒ | If less than the specified value, test the circuit for an open/high resistance. If the circuit tests normal, replace the SDGM. |
| • | PTLAN + APM terminal 2 and PIM terminal 25 |
| • | PTLAN - APM terminal 1 and PIM terminal 24 |
| ⇒ | If greater than the specified range, test the circuit for an open/high resistance. |
| • | PTLAN + APM terminal 11 and ECM terminal 53 |
| • | PTLAN - APM terminal 10 and ECM terminal 33 |
| ⇒ | If greater than the specified range, test the circuit for an open/high resistance. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for module replacement, setup, and programming |
