On February 2, 2017, GM opened a safety investigation resulting from VOQs and customer complaints relating to the loss of EPS.

Between February and April 2017, GM continued to analyze VOQs, customer complaints, and warranty.

Through this analysis, GM was able to link various loss-of-EPS cases as relating to a similar underlying electrical issue. GM then expanded the scope of its field data research to include these various electrical issues to better understand the scope, cause, and effect of the loss of EPS issue.

Between mid-April and May 2017, GM conducted testing and engineering analysis at GM’s Milford Proving Ground on a vehicle exhibiting the loss-of-EPS issue. Through this evaluation, GM gained a better understanding of the effect of this condition and GM conducted further engineering analysis on a specific vehicle to understand the electrical issues causing the loss of EPS. With a better understanding of the potential
electrical issue, investigators were able to more accurately evaluate field data and determine relevant cases, which they did with an extensive final review of VOQ, warranty, and legal claims in early June 2017.

The investigation was reviewed in GM’s Open Investigation Review on June 19, 2017, and on June 22, 2019, GM’s Safety Field Action Decision Authority (SFADA) decided to conduct a safety recall.

General Motors has decided that a defect which relates to motor vehicle safety exists in certain 2014 model year Chevrolet Silverado LD and GMC Sierra LDvehicles.

These vehicles may experience a temporary loss of electric power steering (EPS) assist followed by a sudden return of EPS assist, particularly during low-speed turning maneuvers. The loss and sudden return of EPS assist typically happens within a 1 second period and is caused by an electrical/ software issue.


The information contained in this report was submitted pursuant to 49 CFR §573

Description of the Safety Risk : If EPS assist is lost and suddenly returned, the driver could lose temporary control of the steering wheel, increasing the risk of a crash.
 

Description of the Cause : Events that demand high current, such as low speed turns, can cause temporary low voltage conditions. When the system voltage drops below 8.8
volts for more than 1 second—e.g., during low-speed turns—EPS assist is
disabled until voltage returns to 9 volts for a minimum of 40 milliseconds, at
which point EPS assist returns.

Identification of Any Warning that can Occur :
If power steering assist is lost (i.e., the vehicle reverts to manual steer) a driver
information center (DIC) message may alert the driver to an EPS problem.
Also, other electrical sub-systems may shut down at the same time as or just
before the event, which could temporarily disable the radio, stabilitrack, the DIC, chimes, door-lock cycling, air conditioning, or cruise control.

Vehicle Information :
Vehicle 1: 2014-2014 Chevrolet Silverado LD
Descriptive Information : Certain 2014 Chevrolet Silverado Light Duty vehicles.
Production Dates : JAN 30, 2013 – SEP 04, 2014

Vehicle 2: 2014-2014 GMC Sierra LD
Descriptive Information : Certain 2014 GMC Sierra Light Duty vehicles.
Production Dates : JAN 29, 2013 – SEP 04, 2014

 

Description of Remedy :

Description of Remedy Program: Dealers will perform a reflash of the EPS module software. Pursuant to 577.11, GM will provide reimbursement to owners for repairs according to the plan submitted on May 19, 2017.

How Remedy Component Differs from Recalled Component :
The elevated amperage levels due to high energy demand from the EPS
the module will be greatly reduced allowing the voltage to remain at a
sufficient level to continue operation.

Identify How/When Recall Condition was Corrected in Production :
All Silverado and Sierra vehicles produced after 9/11/2017 will have the
recalibrated software.