The drive motor generator battery control module is also referred to as the battery energy control module (BECM). The BECM will diagnose its own systems and determine when a fault condition is present. Diagnostics and system status is communicated from the BECM to the hybrid powertrain control module (HPCM) through serial data. The HPCM is the host controller for diagnostic trouble code (DTC) information.

The hybrid drive motor generator battery contains 3 high voltage contactor relays also referred to as high voltage (HV) relays. The HV relays allow the high voltage DC batteries to be connected to the vehicle or safely contain the DC high voltage within the drive motor generator battery assembly. The three HV relays are a positive HV contactor relay, negative HV contactor relay, and current limit relay. These relays/contactors close and open in a certain sequence and are controlled by the BECM. The control circuit for the HV relays use a wire from the relay to case ground and the BECM supplies voltage to turn them on and off individually. The BECM monitors the control circuit voltage to these relays and 12 V reference circuit internal to the control module to determine if the circuit is open by comparing the two voltage readings. If the BECM detects 2 consecutive failed high voltage precharge events, a precharge wait time is activated by the BECM. This precharge wait time limit is to allow the precharge circuit internal to the drive motor generator battery assembly to cool down. The precharge wait time counts down in seconds and is displayed on the scan tool.

P0ADB

P0ADC

P0ADB

The control circuit voltage is 2 V less than B+ when the positive contactor relay is commanded closed.

P0ADC

The control circuit voltage is within 2 V of B+ when the positive contactor relay is commanded open.

DTCs P0ADB and P0ADC are type C DTCs.

DTCs P0ADB and P0ADC are type C DTCs.

Schematic Reference

Hybrid Energy Storage Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Drive Motor Battery High Voltage Contactor Relay Operation

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Special Tools

EL-48900 HEV Safety Kit

Ignition ON, command the positive contactor open and closed with a scan tool. Listen for the clicks.

Danger: Always perform the High Voltage Disabling procedure prior to servicing any High Voltage component or connection. Personal Protection Equipment (PPE) and proper procedures must be followed.

The High Voltage Disabling procedure will perform the following tasks:

•	Identify how to disable high voltage.

•	Identify how to test for the presence of high voltage.

•	Identify condition under which high voltage is always present and personal protection equipment (PPE) and proper procedures must be followed.

Failure to follow the procedures exactly as written may result in serious injury or death.
1. Ignition OFF, disable the high voltage at the drive motor generator battery. Refer to High Voltage Disabling.
2. Remove the drive motor generator battery cover. Refer to Drive Motor Battery Case Upper Cover, Front Cover, and Right Side Cover Replacement.
3. Disconnect the X1 harness connector at the positive contactor relay.
4. Test for less than 5 Ω between the ground circuit terminal 2 and ground.

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

5. Connect a test lamp between the control circuit terminal 1 and the ground circuit terminal 2.
6. Connect the 12 V battery.
7. Command the positive contactor relay closed and open with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

⇒	If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the drive motor generator battery control module.

⇒	If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the drive motor generator battery control module.

8. If all circuits test normal, test or replace the positive contactor relay.

Relay Test

Danger: Always perform the High Voltage Disabling procedure prior to servicing any High Voltage component or connection. Personal Protection Equipment (PPE) and proper procedures must be followed.

The High Voltage Disabling procedure will perform the following tasks:

•	Identify how to disable high voltage.

•	Identify how to test for the presence of high voltage.

•	Identify condition under which high voltage is always present and personal protection equipment (PPE) and proper procedures must be followed.

Failure to follow the procedures exactly as written may result in serious injury or death.
1. Ignition OFF, disable the high voltage at the drive motor generator battery. Refer to High Voltage Disabling.
2. Remove the drive motor generator battery cover. Refer to Drive Motor Battery Case Upper Cover, Front Cover, and Right Side Cover Replacement.
3. Ignition OFF, disconnect the positive contactor relay.
4. Test for 23-29 Ω at 20°C (68°F) between terminals 1 and 2.

⇒	If not within the specified range, replace the relay.

5. Test for infinite resistance between the following terminals:

•	X2 and 1 X1

•

X2 and X3

•	X2 and 2 X1

•	2 X1 and X3

⇒	If not the specified value, replace the relay.

6. Install a 20 A fused jumper wire between relay terminal 1 and 12 V. Install a jumper wire between relay terminal 2 and ground. Test for less than 2 Ω between terminals X2 and X3.

⇒	If greater than specified range, replace the relay.

Perform the Diagnostic Repair Verification after completing the repair.