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 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 volt 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.

The BECM compares the High Voltage current limit relay control circuit to the BECMs internal 12 volt measurement reference circuit. This DTC sets when the high voltage current limit relay control circuit voltage and the BECMs internal voltage reference are within 2 volts of each other when the current limit relay is commanded open.

DTC P0AE7 is a Type C DTC.

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

EL-48900 HEV Safety Kit

1. Clear the DTC information.
2. Turn the ignition OFF for 3 minutes.
3. Turn the ignition ON.
4. Retest for DTC P0AE7.
5. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that are captured in 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.
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 volt battery.
4. Disconnect X1 at the HV current limit relay. Connect a test lamp between X1 and ground. The test lamp should not illuminate.

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

5. With a scan tool, command the HV current limit relay CLOSED. The test lamp should turn ON.

⇒	If the test lamp does not illuminate, 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.

6. Disconnect X2 at the HV current limit relay. Connect a test lamp between X1 and X2.
7. With a scan tool, command the HV current limit relay CLOSED. The test lamp should turn ON.

⇒	If the test lamp does not illuminate, test the ground circuit for an open/high resistance and repair as required.

8. Connect the X1 and X2 to the HV current limit relay.
9. Connect a DMM, across X3 and X4 on the high voltage contact side of HV current limit relay. Using a scan tool, command the precharge contactor CLOSED. You should measure less than 0.5 ohms of resistance across the high voltage contact side.

⇒	If the resistance is greater than the specified value, replace the inverter current limit 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 X1 and X2 at the HV current limit relay.
4. Test for 60-70 ohms at 20°C (68°F) between X1 and X2 on the component.

⇒	If not within the specified range, replace the inverter current limit relay.

Perform the Diagnostic Repair Verification after completing the repair.