Probably, most people on this list have not dealt with a Volt unless they are dealer techs. IMO, the Volt, even though it uses over one million lines of code (more than the Space Shuttle), has proven to be one of the most reliable vehicles that G.M. produces.

Naturally, problems will occur with any vehicle. Today, I repaired a 2017 Volt with 2600 miles. The 2017 is the new generation Volt with the more powerful battery, different engine and transmission, and many refinements. The complaint was SES light is on. Scanning the vehicle, I found P1E9E set in the HPCM2. This code is set due to a battery cell group inbalance. In this case, the Interface Control Module 3, Cell Balancing Circuit.

To maintain a similar state of charge on the cell groups, the HPCM2 looks at the cell group voltages and determines which cell groups need energy removed in order to maintain the battery groups at a similar state of charge. This is called cell balancing.

There are no diagnostics for this code as it can only be set due to an internal problem in the BECM, preventing cell balancing to occur. The BECM is mounted above cell group 2 in the HV battery and requires battery removal to replace.

If you've never seen a Gen2 Volt, here's the engine compartment.

[2017 Chevrolet Volt LT, Photo]

The HV battery lowers out the bottom.

[2017 Chevrolet Volt LT, Photo]

These are the battery connectors and coolant ports.

[2017 Chevrolet Volt LT, Photo]

This is the battery with the cover removed. This entire pack is live and great care with the use of PPV equipment is mandated at this point as the pack voltage is 360 volts and will kill you.

[2017 Chevrolet Volt LT, Photo]

This is the BECM mounted above cell group 2.

[2017 Chevrolet Volt LT, Photo]

This last picture shows the pack with the BECM removed. It has 8 connectors and each connector must be unplugged in the correct sequence or damage may occur. Reattachment has a sequence as well. The new BECM needed programming after vehicle reassembly and solved the problem.

[2017 Chevrolet Volt LT, Photo]

James from Florida

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