Some 2016-2019 Volt models may display a Speed Limited to X MPH or Reduced Propulsion Power message on the Driver Information Center (DIC) and limited vehicle propulsion. (Fig. 18) These messages may be intermittent and displayed for a brief amount of time. Once the message clears, full propulsion power is restored to the vehicle. No DTCs will be set.
Fig. 18
The limited propulsion and related DIC messages may be the result of a low transmission fluid level in the drive unit or a mismatch in the estimated battery pack capacity due to the customer’s charging habits.
Check the Fluid Level
Due to the sensitive and complex nature of the drive unit, there are many inputs that the high-voltage (HV) modules and drive unit take into consideration while propulsion is active. In certain instances, such as while taking a sharp corner on a road, a DIC message may display if there is a low fluid level condition in the drive unit.
If these DIC messages are displayed intermittently, inspect for any transmission fluid leaks and verify the fluid level. (Fig. 19) If the fluid level is low or a leak is found, follow the appropriate Service Information procedures to correct the condition.
Fig. 19
TIP: The transmission fluid level must be checked with the transmission fluid temperature at 45–55°C (113–131°F). An under-filled transmission will cause premature component damage. An over-filled transmission may result in overheating and a loss of vehicle propulsion.
Estimated Pack Capacity
A DIC message also may display if there is a discrepancy in estimated battery pack capacity. If a fluid leak is not found and the fluid level is full, review the pack capacity in the Hybrid Powertrain Control Module 2 (HPCM2) and compare it with the Hybrid/EV High Voltage Battery Reduced Range Analysis in the Service Information.
Pack capacity is the deciding factor in determining maximum possible vehicle range when the Hybrid/EV Battery is new and as it ages. Capacity is affected by many factors, including temperature over time, rate of discharge and the normal chemical process over time.
For proper operation, check with the customer that the vehicle is occasionally fully charged, which is how the HPCM2 evaluates the battery. After an extended period of time of not receiving a full charge, or not resting long enough after a full charge, a less accurate battery capacity estimation may be determined, creating a discrepancy between the estimate and the actual pack capacity. Refer to the Hybrid/EV Battery Pack Capacity Learn Procedure – Hybrid/EV Vehicles with Internal Combustion Engine in the appropriate Service Information for more information.
If the DIC messages return and additional assistance is needed, contact the GM Technical Assistance Center (TAC).
For more information, refer to Bulletin #21-NA-204.
– Thanks to Mark Shearer and David Rainey
