2020 Acura MDX

The Office of Defects Investigation (ODI) has received 414 reports of connecting rod bearing failures in the 3.5L V6 engine used in the following vehicles: Model Years (MY) 2018-2020 Acura TLX, MY2016-2020 Acura MDX, MY2016-2020 Honda Pilot, MY2018-2020 Honda Odyssey, and MY2017-2019 Honda Ridgeline.  The subject engine failures were analyzed as part of a Recall Query (RQ24013).  It was determined that these engine failures are outside the scope of Honda Recall 23V-751. Further, evidence gathered in conjunction with RQ24013 does not suggest this failure is caused by the same crankshaft manufacturing defect that is addressed by Honda in Recall 23V-751.  Based on analysis of data from RQ24013, NHTSA has closed that investigation. The significant number of reports of engine failure in vehicles outside the scope of RQ24013 presents a potential safety risk that warrants further investigation.  ODI is opening this Preliminary Evaluation (PE) to further evaluate the scope and severity of the potential problem and to fully assess the potential safety-related issues.  To review the ODI reports cited in the Opening Resume ODI Report Identification Number document, go to NHTSA.gov.

On June 3, 2022, the Office of Defects Investigation (ODI) opened Preliminary Evaluation PE22005 after the agency received VOQs and several field reports concerning the Auto Idle Stop (AIS) feature on 2016-2019MY Honda Pilot vehicles. The complaints allege that the engine fails to restart on its own from a complete stop at a traffic light or road intersection with the AIS function engaged. The subject vehicles are equipped with a 3.5L engine with a 9-speed automatic transmission. On January 6, 2023, Honda released service bulletins 23-008 and 23-009. These service bulletins address the failure to restart issue in the 2016-2019MY Honda Pilot vehicles, as well as the 2015-2020 Acura TLX, 2016-2020 Acura MDX, 2019-2022 Honda Passport, and 2020-2023 Honda Ridgeline vehicles. The repair outlined in the service bulletins is a two-stage countermeasure to remedy the issue. The first stage is a Programmed Fuel Injection (“PGM-FI”) software update. The second stage is only deployed if the software update fails to remedy the issue. The second stage, depending on the model and model year, consists of replacement of the starter assembly, starter relays, and a valve adjustment. Additionally, Honda extended the warranty coverage to 10 years with unlimited mileage for vehicles requiring the second stage component replacement. ODI continues to receive complaints of the AIS failure to restart, with many complainants alleging the campaign countermeasures had been completed.NHTSA has reviewed Honda's Information Request Letter responses involving warranty claims, lawsuits, and consumer complaints in addition to ODI's own data. This Engineering Analysis is being opened to further consider the potential safety defect, including gathering additional data regarding Honda’s service campaign efficacy. ODI is additionally expanding the scope to encompass all vehicles addressed in Honda’s service bulletins 23-008 and 23-009 as well as newer model year vehicles, which are substantially similar to the vehicles covered by the service campaign. To review the ODI reports cited in the Opening Resume ODI Report Identification Number document, go to NHTSA.gov.

On November 8, 2024, the Office of Defects Investigation (ODI) opened Recall Query RQ24013 to assess the scope of Honda recall 23V-751 after receiving complaints that alleged connecting rod bearing failures in vehicles that were not within the scope of recall 23V-751. In November 2023, Honda recalled 248,999 various Model Year (MY)2016–2020 Honda and Acura vehicles equipped with the 3.5L V6 engine. Honda recalled these vehicles due to a crankshaft manufacturing defect that caused premature connecting rod bearing wear and engine seizure. While the out-of-scope failures involved in these complaints appear to have a very similar failure mechanism as the recalled engines, a thorough analysis of all available data from Honda has not indicated that the same manufacturing defect exists in the out-of-scope engines as the engines recalled by 23V-751. Based on this analysis ODI has determined that Honda has properly defined the scope of recall 23V-751. Consequently, ODI will close this RQ investigation.  NHTSA will continue to investigate these complaints of engine failure as part of a new Preliminary Evaluation Investigation (PE25008). The Agency reserves the right to take additional action if warranted by new circumstances.

On XXX, while operating my vehicle, the engine suffered a catastrophic internal mechanical failure due to a broken connecting rod, rendering the vehicle completely disabled and creating a sudden loss of motive power. This vehicle is a 2020 Acura MDX Tech SH-AWD with a 3.5L V6 engine (Engine Code J35Y5). The failure mode experienced is identical to the crankshaft and connecting rod bearing defect detailed in Acura Recall 23V-751 (NHTSA Campaign Number: 23V751000). However, when checking my specific VIN ([XXX]) on the NHTSA lookup tool, it reports 0 unrepaired recalls. My vehicle was excluded from the original recall population despite carrying the exact same engine type, manufacturing year, and experiencing the exact same catastrophic rod fracture resulting from bearing seizure. Because of this severe mechanical failure, the vehicle is un-driveable and requires a complete engine replacement. I am filing this complaint to document that the vehicle population in Recall 23V-751 was too narrowly defined, and to ensure this vehicle is counted in the ongoing NHTSA investigation regarding un-recalled Honda/Acura V6 engine failures. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

NHTSA ID

11776364

Incident

Oct 13, 2026

I purchased my 2020 MDX from the dealership as a new vehicle. I have had to replace the Starter 3 times in 6 years. The dealership covered the replacement of the starter all three times. The first time I was stranded on the road when the starter gave out at a red light. The second time the starter gave out I was in a parking lot. The third time was I was at a gas pump getting gas. I don't think its an appropriate remedy to keep replacing the starter every two years. It seems that there is something wrong with the connection or the circuit system that is making the starter go bad prematurely.

NHTSA ID

11775963

Incident

Oct 31, 2026

While stopped at a stop light the auto restart feature engaged and shut the engine off. When the light turned green and I released the brake pedal the engine did not restart and the battery warning light illuminated. As cars were honking I activated my hazards, had to place the car in park and shut off/restart the vehicle. Luckily it restarted and I was able to proceed home. It activated again while stopped to get mail at mailbox and restarted with no issue. Mileage is 42668. Recall 23-001 PGMfi performed 8/2023. Battery replaced 12/2024.

NHTSA ID

11773527

Incident

Oct 25, 2026

My 2020 Acura MDX fails to restart after the Auto Idle Stop system shuts off the engine at stops. The vehicle stalls and will not restart in active traffic, including busy intersections and high-speed roads. This began about three years ago and now happens every day, leaving my family stranded in live traffic lanes at risk of a collision. On [XXX], the engine shut off and would not restart in the middle of the [XXX], with traffic moving around me at about 40 mph. Capitol Acura in San Jose diagnosed a failing starter motor and ordered a replacement under repair order [XXX]. The part has been on backorder since, with no delivery date. I escalated to American Honda / Acura Client Relations on October 13, 2026 (case [XXX]). On [XXX], Acura replied only that it is "still reviewing" my request. No loaner or alternate vehicle has been provided, and no repair timeline has been given. I am concerned this is a defect affecting other MDX owners: a starter that fails under frequent Auto Idle Stop cycling, combined with a parts shortage that leaves unsafe vehicles on the road. I request that NHTSA review this issue for a possible investigation or recall. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

NHTSA ID

11772865

Incident

Oct 19, 2026

The contact owns a 2020 Acura MDX. The contact stated that the vehicle was previously repaired under Technical Service Bulletins: 22-009, 22-024, and 23-002; however, the failure persisted following the repairs. The contact stated that while stopped at an intersection, the engine failed to restart after the Auto Start/Stop feature engaged, and the transmission independently shifted to Neutral (N). The contact shifted the transmission to Park (P) and pressed the Engine Start/Stop button to restart the vehicle. The vehicle was taken to the dealer, where it was determined that the starter required replacement. The dealer requested that the manufacturer replace the starter; however, the request was denied. The contact associated the failure with NHTSA Action Number: EA25004 (Engine and Engine Cooling). The failure mileage was 70,357.

NHTSA ID

11771392

Incident

Dec 1, 2025

Mileage

70,357 mi

Car is not staying on during traffic. Afraid to go in highway now.

NHTSA ID

11770081

Incident

Oct 6, 2026

On multiple occasions while my car is stopped at a light or stop sign the idle restart stalls and the car shuts off. I need to give it a few minutes and restart the car. It mainly happens when the auto shut off for idling restarts. I have had it happen more than 10X with my kids in the car. I have done all required work - timing belt & water pump replacement, transmission fluid flush, new times and new suspension. It continues to get worse.

NHTSA ID

11768242

Incident

Sep 28, 2026

The contact owns a 2020 Acura MDX. The contact stated that while driving at various speeds, the vehicle hesitated while accelerating. The contact stated that later, while parking the vehicle, the vehicle unintended accelerated and drove over a curb and crashed into a tree. The vehicle crashed into the tree, and the front wheels continued spinning without the accelerator pedal being depressed, and the engine was turned off. During the crash, the front end was severely damaged, but the air bags failed to deploy. The vehicle was driven to the residence and examined by an independent mechanic, and it was determined that the PCM had malfunctioned and there was a computer miscommunication between the engine and the transmission. The vehicle was later towed to the local dealer. The failure mileage was 45,000.

NHTSA ID

11764060

Incident

Sep 11, 2026

Mileage

45,000 mi

Service Bulletin - Under certain circumstances, after coming to a stop and the idle stop feature engages, the vehicle may not automatically restart. In other circumstances, vehicles may experience a slow crank or fail to start under hot ambient temperature conditions.

Dealer Message - Under certain circumstances, after coming to a stop and the idle stop feature engages, the vehicle may not automatically restart. In other circumstances, vehicles may experience a slow crank or fail to start under hot ambient temperature conditions. The customer should be able to restart the vehicle by selecting Park and pushing the ENGINE START/STOP button.

Owner Notification Letter - Under certain circumstances, after coming to a stop and the idle stop feature engaging, the vehicle may not automatically restart. Acura is providing a product update with a new PGM-FI software update to fix this issue.

Dealer Message - Under certain circumstances, after coming to a stop and the idle stop feature engages, the vehicle may not automatically restart. Typically, the client can immediately restart the vehicle by selecting Park and pushing the ENGINE START/STOP button.

Service Bulletin - Under certain circumstances, after coming to a stop and engaging idle stop the vehicle may not restart automatically due to excessive cylinder pressure and/or low cranking torque. Typically, the client can immediately restart the vehicle by selecting Park and pressing the ENGINE START/STOP button.

Service Bulletin - The AWD warning light is on with one or more AWD DTCs having been set due to water intrusion into the electric oil pump motor connector area corrodes the terminals.