2017 Volt Cell Balancing Failure
Posted to Technical Discussion Forum on 6/7/2016
14 Replies
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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