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 the Hybrid LAN communication circuit. The HPCM is the host controller for diagnostic trouble code (DTC) information.

The BECM has several methods of monitoring the total voltage values of the hybrid batteries. The BECM monitors the calculated battery voltage and the terminal voltage. The calculated voltage represents the sum of the voltages from the 20 individual battery measurements. The terminal voltage represents the total DC bus voltage as measured on the output side of the high voltage contactor relays. When the BECM detects that the calculated battery voltage measurement is out of a specified range these DTCs will set.

P1A1F

The calculated battery voltage measurement is less than 168 volts for 4 seconds

OR

Individual hybrid battery voltage measurement is less than 8.4 volts for 4 seconds.

P1A4E

The calculated battery voltage measurement is greater than 408 volts for 4 seconds

OR

Individual hybrid battery voltage measurement is greater than 20.4 volts for 4 seconds.

DTCs P1A1F and P1A4E are Type C DTCs.

P1A1F

P1A4E

Schematic Reference

Hybrid Energy Storage Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

Special Tools

1. Verify that DTC P0B3C, P0B3D, P0B3E, P0B41, P0B42, P0B43, P0B46, P0B47, P0B48, P0B4B, P0B4C, P0B4D, P0B50, P0B51, P0B52, P0B55, P0B56, P0B57, P0B5A, P0B5B, P0B5C, P0B5F, P0B60, P0B61, P0B64, P0B65, P0B66, P0B69, P0B6A, P0B6B, P0B6E, P0B6F, P0B70, P0B73, P0B74, P0B75, P0B78, P0B79, P0B7A, P0B7D, P0B7E, P0B7F, P0B82, P0B83, P0B84, P0B87, P0B88, P0B89, P0B8C, P0B8D, P0B8E, P0B91, P0B92, P0B93, P0B96, P0B97, P0B98, P0B9B, P0B9C, P0B9D, or P0ABB is not set.

⇒	If any of the DTCs are set diagnose them first, refer to Diagnostic Trouble Code (DTC) List - Vehicle.

2. Ignition ON, engine OFF, verify 230-390 volts on the hybrid battery pack calculated voltage parameter using a scan tool.
3. Observe all 20 hybrid battery voltage parameters using a scan tool. All hybrid battery voltage parameters should be within 13-19 volts.
4. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

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.

Important: You must perform the Circuit/System Verification first.

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 case upper cover and right side cover. Refer to Drive Motor Battery Case Upper Cover, Front Cover, and Right Side Cover Replacement.
3. Connect the 12 V battery.
4. Ignition OFF, verify 230-407 volts between terminals HV+ at the HV positive relay and HV- at the HV negative relay.

⇒	If the voltage is between 194-230 volts, perform the jump assist. Refer to Jump Assist.

⇒	If the voltage is less than 194 volts, replace the drive motor generator battery.

⇒	If the voltage is greater than 407 volts, replace the drive motor generator control module.

5. Disconnect the X4 harness connector at the BECM.
6. Connect the EL-48571 to the X4 harness connector.
7. Test for 13-19 volts across all 20 battery voltage reference circuits.

⇒	if not within the specified range, replace the drive motor battery assembly.

⇒	If all circuits test normal, replace the drive motor generator battery control module.

Perform the Diagnostic Repair Verification after completing the repair.