Vehicle Pulls During Regenerative Braking

Some 2011-2019 Volt, 2014-2016 ELR, 2017-2019 CT6, and 2017-2019 Bolt EV models may pull to the left or right when the regenerative braking paddle on the back-left side of the steering wheel (Fig. 22) is used and/or when braking with the brake pedal.

 

Fig. 22

 

The first step in diagnosis of the pull condition is to inspect the vehicle’s tires. The most common cause is usually related to incorrect tire pressure, tire wear or uneven tread depth, an incorrect installed tire or a mis-matched brand of tires.

The regenerative braking system on these models applies torque evenly to both axles while braking in a straight line. (Fig. 23) Pulling to one side or the other is not caused by the propulsion system.

 

Fig. 23

 

During regenerative braking, when the vehicle is coasting or braking, the drive motor generator power inverter module operates the drive motor as a generator. Operating as an electrical generator, the drive motor exerts a driveline load that helps to slow the vehicle. The electrical energy that the drive motor creates is transferred by the drive motor generator power inverter module to the hybrid/EV battery pack. Constant communication between the drive motor generator power inverter module and the electronic brake control module allows the blending of regenerative braking force with hydraulic braking force.

To verify that the tires are in the proper condition, inspect the tires for wear and correct installation. Also correct the tire pressure, if necessary. Authorization will be needed to replace any tires if needed. Review Bulletin #00-03-10-003 (U.S.) or #01-03-10-003 (Canada) for what constitutes tire damage vs. normal wear and tear.

If none of the conditions are present with any of the tires, switch the front tires to the rear to see if the pull condition goes away or is lessened. If the pull is less, it may be necessary to replace those tires on the rear of the vehicle.

If the pull condition is still present, get authorization to replace all four tires and wheels from another vehicle to determine if the pull condition goes away. If the tires are confirmed to be good, follow further diagnostics in the appropriate Service Information.

 

– Thanks to Chuck Wieseckel and Lane Rezek

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