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U189A




DTC U189A

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.

* Diagnostic Procedure Instructions 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 Module

Diagnostic Fault Information






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 V.

* 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 (with RPO SLT) Instrument Panel Center Trim Panel Replacement (with RPO SLT).

* 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

* Data Communication Schematics Electrical Diagrams

* Control Module References Control Module References

Connector End View Reference

Component Connector End Views 1-2 Shift Solenoid (SS) Valve (M30)

Description and Operation

Data Link Communications Description and Operation Description and Operation

Electrical Information Reference

* Circuit Testing Circuit Testing

* Connector Repairs Connector Repairs

* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections

* Wiring Repairs Wiring Repairs

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 Diagnostic Trouble Code (DTC) List - Vehicle to diagnose that DTC prior to this diagnostic.

Circuit/System Testing

1. Ignition OFF, test for less than 1.0 ohms between the drive motor generator power inverter module case and ground strap.

• If greater than the specified value, test the ground circuit for an open/high resistance.

2. Ignition OFF, disconnect the harness connector X1 of the drive motor generator power inverter module.

3. Ignition ON, verify that a test lamp illuminates between each of the following B+ circuit terminals and ground.

* Terminal 6 X1

* Terminal 7 X1

• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit fuse is open, test the control circuits of the drive motor generator power inverter module for a short to ground. If the circuits test normal, replace the drive motor generator power inverter module.

4. Ignition ON, verify that a test lamp illuminates between each ignition circuit terminal 20 X1 and ground.

• If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit fuse is open, test the control circuits of the drive motor generator power inverter module for a short to ground. If the circuits test normal, replace the drive motor generator power inverter module.

5. Ignition ON, verify that a test lamp illuminates between the wakeup circuit terminal 19 X1 and ground.

• If the test lamp does not illuminate, test the entire circuit for an open/high resistance or short to ground. If the circuits test normal, replace the serial data gateway (SDG) module.

6. Ignition OFF, disconnect the harness connector X1 of the accessory DC power control module.

7. Test for less than 2 ohms between the following powertrain serial data circuit terminals.

* Accessory DC power control module terminal 2 X1 and drive motor generator power inverter module terminal 25 X1

* Accessory DC power control module terminal 1 X1 and drive motor generator power inverter module terminal 24 X1

• If greater than the specified range, test the circuit for an open/high resistance.

8. Ignition OFF, disconnect the harness connector X3 of the engine control module (ECM).

9. Test for less than 2 ohms between the following powertrain serial data circuit terminals.

* Drive motor generator power inverter module terminal 11 X1 and ECM terminal 53 X3

* Drive motor generator power inverter module terminal 10 X1 and ECM terminal 33 X3

• If greater than the specified range, test the circuit for an open/high resistance.

10. If all circuits test normal, replace the drive motor generator power inverter module.

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests after completing the repair.

* GMLAN Wiring Repairs GMLAN Wiring Repairs

* Control Module References Control Module References for module replacement, programming and setup

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