Cover BDU Electrical Connectors Before Removing Coolant Hoses

The Drive Motor Battery, or high voltage hybrid/EV battery, on 2011-2019 Volt models (Fig. 26) is cooled or heated in order to maintain a proper temperature that aids system performance and longevity. The energy storage system cooling system uses a 12 V hybrid/EV battery pack coolant pump, a refrigerant/coolant heat exchanger (chiller) and the electric A/C compressor motor control module assembly to cool down the high voltage hybrid/EV battery. There is also a high voltage heater inside the hybrid/EV battery to heat the coolant entering the hybrid/EV battery when needed. The hybrid/EV battery pack cooling system circulates a pre-mixed DEX-COOL solution, which is a 50/50 mixture of DEX-COOL coolant and de-ionized water.


Fig. 26


Any time the high voltage battery pack is removed from the vehicle, extra caution must be used so that coolant does not enter any of the electrical connections.

The Drive Motor Battery Replacement procedure in the appropriate Service Information instructs to install smoke test adapters (smoke plugs) or equivalent on the electrical connectors of the BDU before removing the coolant hoses that go into the battery pack. (Fig. 27) If the smoke plugs are not used, there is the possibility that any coolant from the hoses may splash onto the connectors and cause corrosion, quickly leading to an electrical concern. In most cases, DTC P1EC3 (Hybrid/EV Battery Pack Heater Transistor Control Circuit) will be set in the Hybrid Powertrain Control Module 2 (HPCM2) if the connectors become corroded.


Fig. 27


Smoke Plugs for Gen 1 and Gen 2

On 2011-2015 Volt models (Generation 1), use the EL-50812 Battery Leak Test Kit, which includes low voltage connector plugs and high voltage connector plugs specific to Gen 1 models. (Fig. 28)


Fig. 28


On 2016-2019 Volt models (Generation 2), use the High Voltage Battery Smoke Test Adapters from the EL-51753 Battery Leak Test Kit, which are high voltage connector plugs specific to Gen 2 models (Fig. 29), and the low voltage connector plugs from the EL-50812 Battery Leak Test Kit.


Fig. 29


Correct Procedure

TIP: Prior to servicing any High Voltage component or connection, always perform the High Voltage Disabling procedure. Personal Protection Equipment (PPE) and proper procedures must be followed.

Behind the underbody air deflectors, there are two electrical connectors at the front of the Drive Motor Battery. (Fig. 30)


Fig. 30


After disconnecting the electrical connectors, cover the connectors using the proper smoke test adapters (smoke plugs) or equivalent. The smoke plugs will prevent any coolant from contaminating the electrical connectors when the coolant ports are disconnected. (Fig. 31)


Fig. 31


Do not remove the Driver Motor Battery cooler outlet or inlet hoses without first installing the smoke plugs on the electrical connectors. Coolant that splashes onto the connectors will cause corrosion. (Fig. 32)


Fig. 32


– Thanks to Dave Rainey

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