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.

P0ADF

P0AE0

P0ADF

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

P0AE0

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

DTCs P0ADF and P0AE0 are type C DTCs.

DTCs P0ADF and P0AE0 are type C DTCs.

Schematic Reference

Hybrid Energy Storage Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Drive Motor Battery System Description

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Special Tools

EL-48900 HEV Safety Kit

Ignition ON, command the negative contactor relay open and closed with a scan tool. Listen the for the contactor relay 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. Connect the 12 V battery.
4. Disconnect the inline X1 harness connector at the negative contactor relay.
5. Ignition OFF and scan tool disconnected, open and close the driver door, and wait 1 minute. 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.

6. Connect a test lamp between the control circuit terminal 1 and the ground circuit terminal 2.
7. Command the negative contactor relay open and closed 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 negative contactor relay.

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 negative contactor relay.
4. Test for 23-29 Ω at 20°C (68°F) between the cotnrol terminal 1 and the ground terminal 2 of the negative contactor relay.

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

Perform the Diagnostic Repair Verification after completing the repair.