Mazda MAZDA3 lane assist problems

Filed Nov 19, 2025 · Electrical, Engine · TX

My 2018 Mazda 3 has an intermittent electrical failure on the high-speed CAN network that causes multiple safety-critical systems to fail while driving. When the fault occurs, the dash lights up with warnings for powertrain, ABS/traction, lane departure, collision-avoidance, TPMS, immobilizer, and the check-engine light. The car also hesitates or “lurches” between 15–30 mph during these events. At one point in 2024, the vehicle went into limp mode on the freeway, creating a safety hazard. These failures are intermittent but repeatable. Diagnostic scans from 2023–2025 show multiple U-codes for lost communication between control modules; two later became permanent. The issue appears unrelated to any one component and affects many systems at once. The vehicle has been to every Mazda dealership in the North Texas region (Mesquite, Freeman, Hiley, Norm Reeves, Town North). All performed only basic scans; none completed a full CAN-bus or wiring-harness diagnostic. Town North kept the vehicle for six weeks (Sept–Oct 2025), replaced a coil and spark plugs, performed a camera calibration and a TCM update, but the network failures returned within 38 miles. We sought independent inspection only after dealerships repeatedly refused diagnosis whenever the warning lights were not on at the moment of arrival. In November 2025, a technician found significant internal corrosion inside the negative battery cable; touching the cable reproduced the full failure immediately. The corrosion extends deep into the wire sheathing. This appears to be an electrical defect affecting CAN communication and power/ground integrity. When the fault occurs, multiple safety systems disable at once and the vehicle behaves unpredictably. Mazda Corporate has declined further assistance, and the defect remains unresolved. I am filing this report because this is a recurring safety issue that may affect other vehicles of the same model and year.

Filed Jun 8, 2024 · Driver assistance, Electrical · VA

The collision warning light and lane assistance light come on frequently. It used to just be when the weather was under 40 degrees and the car was cold. However, it now happens all the time. It seems to go on and off for no reason. Additionally, the infotainment system keeps switching radio stations or ghosting without anyone touching it. It also drops Bluetooth connectivity constantly.

Filed Apr 15, 2024 · Driver assistance, Electrical · 31,321 miles · TX

The contact owns a 2018 Mazda Mazda3. The contact received notification of the federal safety agency Campaign Number: 23V487000 (Back Over Prevention) however, the part to do the recall repair was not yet available. The contact stated that the manufacturer had exceeded a reasonable amount of time for the recall repair. The manufacturer was made aware of the issue. The contact stated while driving 40 MPH, the parking brake light illuminated, and the vehicle decelerated and was losing motive power. The contact pressed the parking brake button off and on and the warning light stopped, and the contact was able to drive normally. Additionally, the contact stated that in other instances the forward sensing camera and the lane departure systems were also independently engaging. The contact stated that it was difficult to maintain the lane she was driving in. The contact stated that several unknown warning lights were illuminated. The contact stated that the failure occurred at various speeds. The contact drove the vehicle to a dealer who diagnosed the vehicle and flashed the Powertrain Control Module (PCM). The vehicle was repaired. The contact stated that the failures reoccurred and the battery short-circuited. The contact had taken the vehicle to a non-manufacturer dealer who used a handheld scanner and retrieved the following codes: C1001 Type 97, U3003, and B13D3. The vehicle was not repaired. The failure mileage was 31,321. VIN tool confirms parts not available.

Filed Feb 5, 2024 · Driver assistance, Electrical · 1,900 miles · MA · crash

The contact leased a 2024 Mazda Mazda3. The contact stated that while driving at 55–60 mph, the windshield wipers continued to stay in the on position and failed to turn off. The parking brake engaged without application and turned on and off. All the electrical systems malfunctioned and failed to turn off. The lane assist engaged and forced the vehicle to crash into the side wall. All the instrument cluster warning lights were illuminated. There were no reported injuries. There was no police report filed. There was no air bag deployment or fire. The vehicle was taken to the local dealer, where the mechanic reset the codes. The mechanic informed the contact that the malfunction may continue while traveling over a bump. The vehicle was not diagnosed or repaired. The manufacturer was contacted regarding the failure and opened a case. The approximate failure mileage was 1,900.

Filed Jun 12, 2023 · Driver assistance, Steering · NY

Lane departure warning activated and attempted to correct during a gentle curve. The location had shifted lanes due to construction, so clear lines were visible but not the actual lane to follow which is a frequent occurrence in New York City. The system came close to steering me into the adjacent lane occupied by another vehicle forcing me to fight the correction. There was a lane departure warning on the dash and I believe the blind spot indicator was on (i.e. the adjacent vehicle was detected in some capacity). I considered this especially dangerous as in this zone also had very tight lanes so my physical correction could have also caused an accident. There was no malfunction of the physical components. No dealer or service center has reproduced the issue however I have discussed with other drivers of the same line (2020-23 Mazdas) who have had similar experiences leading to a decision to disable these "safety" features. Mazda provides a reasonable description of scenarios where lane departure and assistance will disable itself due to poor conditions or low confidence. I would recommend at a minimum requiring the system to detect and potentially differentiate lane widths, as city driving sometimes has extremely tight lanes (for example, the inner roadway of the Williamsburg Bridge where two adjacent lanes are perhaps 8-9ft with less than 2ft on either side to the wall). In these scenarios, any steering correction at all is more dangerous than if it were off.

Filed Jan 22, 2022 · Acceleration, Electrical · CA

Context: ADAS was not on. Lane keep assist is disabled in system settings entirely as it is dangerous. Blinkers were on, I was pulling out from parallel parking into left turn lane onto a straight road with slight incline. Car is of the Turbo trim on stock tires. Upon finishing pulling out of parallel parking spot and gassing the car, torque vectoring or some underlying collision avoidance may have phantom activated. I felt torque shift to the wrong tires, unsettling the car, and the wheel -- with no human input -- jerked to the left to force me into the lane left of intended. I applied throttle and steered right back into the correct lane, but the car was applying torque to the wrong tires and applying a left bias to the steering. Only after I got above 25mph and held straight did the car settle. Almost caused an accident if the lane was not empty due to car unsettling itself into the left lane.

Filed Sep 28, 2021 · Driver assistance · CO

The error code "B14FO-76 FORWARD SENSING CAMERA DEVIATION - WRONG MOUNTING POSITION" was discovered, and verified, by a Safelite Auto Glass service center when the 2021 Mazda 3 was in for a repair (stone chip) to the windshield on September 21, 2021. There were no warning messages nor lights to alert the driver as to the improper installation/mounting of this device. There has been no known modification to nor obstruction of the FSC -- its condition is now as it was received new from the dealer. Improper mounting ("Wrong Mounting Position") of the Forward Sensing Camera affects multiple safety systems of this vehicle, which affects the safety of the vehicle's passengers as well as everyone's safety around the vehicle every time it is driven -- there's no telling what injury and damage may occur from an errant un-commanded driving tasks such as emergency braking and faulty lane departure corrections.

Filed Aug 4, 2020 · Driver assistance, Electrical · 1,491 miles · WI

Tl* the contact owns a 2019 mazda mazda3. The contact stated that the brake auto alarm activated causing the brakes to engage. The contact stated the vehicle was included in 19v907000 (forward collision avoidance) for which the remedy was completed. The contact stated the failure persisted. The contact stated that the vehicle network malfunction warning light, vehicle inspection needed, safety and driver support system disabled and front radar obscured warning lights were illuminated. Additionally, the lane departure alarm activated, and the auto correct activated causing the vehicle to pull both to the left and right. The contact took the vehicle to the dealer (russ darrow metro mazda - address: 11330 w metro auto mall drive, milwaukee, wi 53224 phone: (414) 409-9201) who performed the recall remedy along with 8 other unspecified recall repairs however, the failures persisted. The manufacturer was made aware of the failures and a case was filed. The approximate failure mileage was 1,491.

Filed Dec 2, 2019 · Driver assistance, Visibility · 4,655 miles · CA

I was driving about 30 MPH or slower in a light rain on a city street when my vehicle said that the front radar failed/unable to function, all safety systems are now disabled. This lasted for about 3-4 minutes and then it started to function again but only for 2 minutes and then it gave the same message and disabled all my safety systems while again. It started to function again as I pulled into my driveway which is why I was unable to get a photo. I have had multiple ongoing problems with lane departure warning and with the windshield wiper sensor and the doors and trunk locking and unlocking. I think the entire electrical system is defective and most of the problems come from the front radar but there are so many problems with the electronics that I this this vehicle is a lemon. The lane-keep assist is so bad it has almost made me crash on 3 separate occasions so I have disabled it.

Filed Jul 2, 2019 · Electrical · 1,300 miles · MD

The entire vehicle safety system malfunctions at random times while driving, most recently on the highway. The dashboard illuminates stating "safety and driver support systems partially disabled, drive safely". I lose blind spot monitoring, lane keep assistance, radar, and city brake support, among other things. This has happened several times over the past 2 weeks.