2024 Cadillac Lyriq

On August 9, 2026, at approximately 3:40 a.m., while driving, the vehicle suddenly lost all propulsion and became completely disabled on the roadway. The vehicle remained powered on but would not move forward or backward. At approximately the time of the failure, Cadillac/OnStar Advanced Diagnostics generated a critical Electric Drive Unit warning instructing immediate service and reported diagnostic code P0A78. Additional vehicle diagnostic warnings involved the electric drive unit/high-voltage propulsion system. I immediately contacted roadside assistance but was unable to obtain a workable towing solution for several hours. The vehicle ultimately had to be privately towed and has remained undriveable since the incident. The loss of propulsion occurred unexpectedly while the vehicle was being driven, without advance warning that would have allowed me to safely plan for the vehicle to become disabled. I am concerned that the same sudden loss of propulsion could occur at higher speed, in traffic, at an intersection, or in another location where an unexpected loss of motive power could create a serious crash risk. The vehicle requires diagnosis and repair for the Electric Drive Unit/P0A78 condition.

Hi, this vehicle is owned by Surreal Development LLC. A company whom reverse engineers vehicle. GM has an issue in their Cadillac Lyriq's which causes a complete failure of the vehicle's communication systems without warning while driving. This issue appears to affect all Global B vehicles but it is most severe in vehicles with one pedal driving (Sierra EV, Lyriq, Blazer EV, Optiq, Silverado EV, Equinox EV, etc...) The error is likely within the vehicle's Serial Data Gateway Control Module but it is unclear. The vehicle recovers from the communication quickly (within seconds) but it causes long term adverse affects for that driving period. 1. The vehicle will light up with warnings (Service Traction Control, disengage super cruise, disengage ACC, etc...) 2. The driver's pedal will go into safety mode. 3. A "Service High Voltage" system warning may or may not appear. The safety concern is mostly in #2. When this happens it is very jarring to the driver as it drastically changes how the vehicle responds. While the vehicle may state one pedal driving is disabled many times it still indicates it is on within the controls (likely due to an error in the compounded communication fault). This can lead to the driver rear ending the vehicle in front of them or rolling over. The fault does not correct itself until the vehicle resets (powers off/on). The issue is common and affects many owners of the Cadillac Lyriq. The only diagnostic data we see are communication faults across many modules.

This is an update to my original NHTSA complaint submitted on May 5, 2025 (complaint number 11658852), regarding a complete electrical failure in a 2024 Cadillac Lyriq. While parked in a garage, the vehicle experienced a full shutdown—rendering all systems inoperable, including the door locks and windows. Most alarmingly, a [XXX] child was trapped in the back seat due to the doors being electronically locked and unresponsive. The dealership has since diagnosed the failure as a cable routed improperly near the steering column that had rubbed against a component and snapped. This severed connection resulted in the complete loss of vehicle power and emergency functions. Since that time, I have discovered multiple similar reports from other Lyriq owners online describing full system shutdowns, locked doors, and failures to start—many of which are shared on public forums such as Reddit [XXX] ). This suggests that this may not be an isolated case but rather a potential systemic defect in the Lyriq's wiring harness design or electrical architecture. I am extremely concerned that this failure mode could occur while driving, particularly at highway speeds, and would result in loss of steering, braking assist, and emergency exit options. I urge the NHTSA to investigate this issue further to determine whether a recall or manufacturer communication is appropriate. This vehicle is currently with the dealership, and I have refused delivery until GM provides formal safety assurances. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

I purchased a brand new Cadillac Lyriq on July 1, 2024, and have encountered several severe issues that compromise the safety and reliability of the vehicle: 1.Display Failure: The display frequently flickers, flashes, and sometimes completely blacks out, causing the loss of critical information such as speed, backup camera, navigation, and other vital systems. This makes the vehicle unsafe to drive, as it is impossible to monitor speed and other essential functions necessary for safe operation. 2.Battery Overheating During DC Fast Charging: The vehicle’s battery consistently overheats during DC fast charging sessions, causing the charge rate to drop significantly (from ~190 kW down to 14-20 kW). This overheating issue not only drastically extends charging times but also raises serious safety concerns, particularly during long road trips in hot weather. The vehicle has repeatedly experienced these issues, making it unreliable for long-distance travel. 3.Charger Overheating and Instability During Home AC Charging: The home AC charger provided with the vehicle becomes excessively hot while charging the Lyriq. Additionally, the charging rate fluctuates erratically between 0-3 kW, further complicating the charging process. This overheating of the charger at home raises concerns about the safety of parking or charging the vehicle in my garage, as it may pose a fire risk. These issues have been reported to my dealership, who have attempted repairs without success. The problems persist, and the vehicle remains unsafe and unreliable for my family’s needs. I am deeply concerned about the potential for these issues to lead to more severe safety incidents if not addressed promptly.