— Acura MDX and RDX acceleration problems have caused a class action lawsuit that alleges the SUVs suffer from sudden hesitation on acceleration, transmissions that shift into NEUTRAL, warning lights that illuminate and engines that stall.
According to the plaintiff, 2016-2020 Acura MDX and 2019-2020 Acura RDX SUVs have problems with miscommunications between the computers and software that control the transmissions, throttles and engines.
The Acura MDX and RDX acceleration problems allegedly leave drivers without vehicles that provide safe and reliable transportation because the SUVs enter "limp mode" without warning.
The class action was filed by plaintiff Roby Partovich, who says he purchased a new 2019 Acura MDX in December 2018 from a California Acura dealership.
The plaintiff says he was driving on a highway in March 2020 when the MDX suddenly decelerated from 75 miles per hour to 45 mph on two occasions in about 20 minutes. He says he took the MDX to a dealer but was told there was nothing wrong with the vehicle, so no repairs were performed.
Later that month the MDX allegedly decelerated to a stop without him touching the brake pedal. The plaintiff says he took the SUV to a dealer but no repairs were performed because technicians said nothing was wrong with the vehicle.
The plaintiff filed the class action after the last dealer visit, and his MDX allegedly still experiences the problem.
According to the Acura lawsuit, the engine control modules (ECMs) and the transmission control modules (TCMs) are some of the components involved, and the plaintiff says the ECM may also be known as the powertrain control module (PCM).
The Acura vehicles are equipped with drive-by-wire throttle systems which to operate correctly must allegedly have ECM/PCM and TCM systems that communicate with each other. But the MDX and RDX lawsuit says the systems don't do that, which leads to acceleration and other problems.
According to the class action, instead of cables, a drive-by-wire vehicle uses a sensor attached to the gas pedal to measure how far the pedal has been depressed. That measurement is sent to the throttle control computer which then sends a command to the throttle body to limit or expand the amount of air going into the engine.
Both the ECM and the TCM also send information to the throttle control computer so the throttle can be adjusted during gear changes or change the way the throttle reacts when the gas pedal is pressed.
The lawsuit says if the throttle is stuck open, a vehicle can shift into NEUTRAL or a limp mode in order to prevent engine, transmission or other vehicle damage. But if the throttle does not respond to the command to open, it will fail to allow more air into the engine.
The Acura MDX and RDX SUVs allegedly have defects where the throttles receive conflicting information from the gas pedals and modules, causing the throttles to malfunction.
According to the class action, Honda/Acura knows about the problem from consumer complaints and other sources, complaints that caused the automaker to issue technical service bulletins to dealerships.
In July 2015, Honda sent dealerships TSB 15-034 about the 2016 Acura MDX, titled “Product Update: Vehicle shifts into Neutral and MIL Comes On with DTC P0657.”
“While driving, the vehicle shifts into Neutral, the transmission indicator comes and DTC P0657 (actuator supply voltage circuit/open) is stored. The driver will not be able to select any other gear until the vehicle is turned off and restarted. Update the PGM-FI [programmed fuel injection] software and the TCM software, clear any DTCs [diagnostic trouble codes], and do the PCM [powertrain control module] idle learn procedure.” - TSB 15-034
However, the plaintiff argues the software update failed to repair the vehicles.
In September 2019 Honda issued TSB B18-045, titled “Update: F-CAN [Fast Controller Area Network] Bus Connected Unit Check” that applied to the 2019 Acura RDX and 2019 Acura MDX Sport Hybrid.
The class action says the bulletin describes troubleshooting methods for a loss of communications such that “certain control units that may be reported as Not Available in the Status column even though they are properly communicating.”
However, the plaintiff argues the alleged repairs didn't help the SUVs.
Finally, in January 2019, model year 2016-2018 Acura MDX SUVs, along with other models, were recalled to prevent the vehicles from stalling due to the fuel pumps. The automaker said dealerships would update the fuel injection engine control unit software (FI-ECU), and in some cases replace the fuel pumps.
However, the plaintiff argues the alleged repairs didn't help the SUVs.
The plaintiff says hesitation on acceleration and sudden deceleration cause serious safety hazards to Acura occupants, other consumers on the road and to property.
The lawsuit about Acura MDX and RDX acceleration problems was filed in the U.S. District Court for the Southern District of California: Partovich, et al., v. American Honda Motor Company, Inc., et al.
The plaintiff is represented by Capstone Law APC, and Berger Montague PC.
CarComplaints.com has complaints from drivers of Acura MDX and Acura RDX SUVs.