← New search

2015 Kia Optima

Owner reports · Recalls · Investigations

More warning signs than most Optima years

Owner complaints for the 2015 Kia Optima are substantially higher than the model-year median of 186.5.

About this comparison →

When problems were reported

Mileage at the reported incident

493 reports with mileage · 514 unknown

NHTSA’s mileage field refers to the reported incident, not necessarily the filing date. This shows report counts, not the likelihood of a failure.

What to inspect

Issues worth paying extra attention to based on owner reports.

  • Engine. Review the 621 owner reports in this category and discuss these concerns during a pre-purchase inspection. Read reports →
  • Electrical System. Review the 135 owner reports in this category and discuss these concerns during a pre-purchase inspection. Read reports →
  • Structure. Review the 76 owner reports in this category and discuss these concerns during a pre-purchase inspection. Read reports →

NHTSA owner reports · September 18, 2026 snapshot.

31 crash reports74 fire reports20 injury reports

Electrical System complaints

135 reports
Clear category filter
88,000 miles · Jul 29, 2026
Electrical System

The contact owns a 2015 Kia Optima. The contact stated that while driving at an undisclosed speed, the brake pedal was depressed; however, the rear taillight socket wiring harness failed to function as intended. The contact was informed that the brake lights were inoperable. The contact stated that the failure had occurred every…

Read full complaint

The contact owns a 2015 Kia Optima. The contact stated that while driving at an undisclosed speed, the brake pedal was depressed; however, the rear taillight socket wiring harness failed to function as intended. The contact was informed that the brake lights were inoperable. The contact stated that the failure had occurred every 6–7 months. The contact stated that the repair was completed by the contact. The dealer was not made aware of the failure but provided no assistance. The vehicle was not diagnosed or repaired by an independent mechanic or dealer. The manufacturer was not made aware of the failure. The failure mileage was approximately 88,000.

NHTSA ODI #11753610

Mileage unknown · Jul 14, 2026
Electrical SystemService Brakes

I would say that the time this incident happened I was driving and me and me nephew were in car at time taking to shop to see why it was making a sound like air and all of sudden the car started swerving and slowing down and then it made a pop sound and smoke started coming from the car and I was thankful that I didn’t get hit …

Read full complaint

I would say that the time this incident happened I was driving and me and me nephew were in car at time taking to shop to see why it was making a sound like air and all of sudden the car started swerving and slowing down and then it made a pop sound and smoke started coming from the car and I was thankful that I didn’t get hit but affraid and also hit my head in car due to the sudden jerk car mad and then it popped sound a d smoke came from good. The next day I have to pay to get back on the other side and also tow it home which it been parked since but I see a recall on my vin and want to find out how to get it to the nearest Kia to fix the recall

NHTSA ODI #11750184

Mileage unknown · Jun 22, 2026
Electrical SystemEngine

1. What component or system failed or malfunctioned, and is it available for inspection upon request? The primary failure involved the engine. The vehicle experienced a major engine failure that resulted in an engine replacement under a manufacturer recall. After the replacement engine was installed, the vehicle later developed …

Read full complaint

1. What component or system failed or malfunctioned, and is it available for inspection upon request? The primary failure involved the engine. The vehicle experienced a major engine failure that resulted in an engine replacement under a manufacturer recall. After the replacement engine was installed, the vehicle later developed additional engine-related problems. An independent mechanic advised that the vehicle would require another engine replacement or extensive engine repairs. Additional defects included a malfunctioning moonroof that would no longer close properly and other mechanical issues affecting the vehicle's operation. The vehicle may be available for inspection depending on its current status and location. 2. How was your safety or the safety of others put at risk? The repeated engine problems created concerns about the reliability and safe operation of the vehicle. Sudden engine failure while driving resulted in loss of power, inability to maintain speed in traffic, and being stranded in unsafe conditions. The ongoing mechanical failures caused significant concern regarding the vehicle's dependability and safety. 3. Has the problem been reproduced or confirmed by a dealer or independent service center? Yes. The original engine issue was confirmed by authorized service personnel and resulted in an engine replacement under a manufacturer recall. The subsequent engine-related problem was evaluated by an independent mechanic, who advised that the vehicle required another engine replacement or significant repairs. 4. Has the vehicle or component been inspected by the manufacturer, police, insurance representatives, or others? The vehicle was inspected in connection with the original engine recall and replacement. It was also inspected by an independent mechanic regarding the subsequent engine issues. At this time, I am not aware of any inspection by police or insurance representatives related to these mechanical failures. 5. yes, right away

NHTSA ODI #11745534

174,000 miles · Mar 17, 2026
Electrical SystemEngineFire

The contact owned a 2015 Kia Optima. The contact stated that while driving at 60 MPH, during a DoorDash delivery, the vehicle vibrated. The contact pulled to the side of the road and noticed smoke emitting underneath the vehicle from the right side. The contact exited the vehicle and noticed smoke emitting from underneath the ho…

Read full complaint

The contact owned a 2015 Kia Optima. The contact stated that while driving at 60 MPH, during a DoorDash delivery, the vehicle vibrated. The contact pulled to the side of the road and noticed smoke emitting underneath the vehicle from the right side. The contact exited the vehicle and noticed smoke emitting from underneath the hood. The state troopers were called. By the time the fire department arrived, the vehicle was engulfed in flames, and the engine had exploded. The fire department extinguished the fire. The contact was not injured. No police report was filed. The state troopers believed that the fire was caused by an electrical short. The contact stated that prior to the fire, the vehicle vibrated when idled. No warning lights were illuminated. The vehicle was towed to a towing yard. The insurance company was not notified about the fire. The contact was unaware that NHTSA Campaign Number: 21V331000 (SERVICE BRAKES, HYDRAULIC) was associated with the VIN. The manufacturer was not notified of the fire. The failure mileage was approximately 174,000.

NHTSA ODI #11725022

Mileage unknown · Jan 25, 2026
Electrical SystemSteeringFire

Yesterday, [XXX], My 2015 kia optima engines reved up wothout me pushing the gas & within seconds later a loud noise and metal fell from under the hood. After pulling over, popping the hood on the passenger side and under the engine a fire had started. My daughter was seated in the back passenger side her door had locked, thankf…

Read full complaint

Yesterday, [XXX], My 2015 kia optima engines reved up wothout me pushing the gas & within seconds later a loud noise and metal fell from under the hood. After pulling over, popping the hood on the passenger side and under the engine a fire had started. My daughter was seated in the back passenger side her door had locked, thankfully the passenger door was left opened bc within minutes the entire car was filled with smoke and engulfed in flames. Prior to this the steering wheel would jerk even while at a red light. This car just did have 100,000 miles & no knowledge this prior. Thank god i was able to get my daughter out of this vehicle & this didnt end in a tragedy due to negligence if this was a prior known fact. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

NHTSA ODI #11713230

Mileage unknown · Jan 17, 2026
Electrical SystemExterior LightingUnknown Or Other

I’ve gotten my vehicle fixed four times now thinking it was an electrical issue, not aware of the recall. Did my research this fifth time when my brake lights completely went out and smoke at some point in times come through my air-conditioning. I’ve spent more money trying to fix the vehicle with no idea that there were issues …

Read full complaint

I’ve gotten my vehicle fixed four times now thinking it was an electrical issue, not aware of the recall. Did my research this fifth time when my brake lights completely went out and smoke at some point in times come through my air-conditioning. I’ve spent more money trying to fix the vehicle with no idea that there were issues already about it.

NHTSA ODI #11711673

Mileage unknown · Jan 2, 2026
Electrical SystemService BrakesSteering

My 2015 Kia Optima has a failing ABS/HECU module consistent with the Kia ABS fire recall. The brake lights stay on constantly even when the brake pedal switch is unplugged. If I unplug the ABS/HECU module, the brake lights immediately turn off, which confirms the ABS module is back-feeding power into the brake light circuit. I …

Read full complaint

My 2015 Kia Optima has a failing ABS/HECU module consistent with the Kia ABS fire recall. The brake lights stay on constantly even when the brake pedal switch is unplugged. If I unplug the ABS/HECU module, the brake lights immediately turn off, which confirms the ABS module is back-feeding power into the brake light circuit. I also previously experienced the ABS pump running with the vehicle turned off. Currently the ABS, ESC, EPS, and Brake warning lights are illuminated and all stability/ABS functions are disabled. This is a clear safety hazard affecting braking, electrical safety, and vehicle fire risk. I have already been to the Kia dealer twice and they dismissed the issue after only checking the recall fuse. They refused to address the ABS module itself even though the vehicle is unsafe. The recall appears insufficient because the module has now failed. I need Kia to replace the ABS/HECU module under recall safety remedy.

NHTSA ODI #11708255

Mileage unknown · Dec 9, 2025
Electrical System

In September of 2025, my radio and back up camera stopped working. I contacted Hayward Kia and was informed by staff member, Eraca Craig, that my 2015 Kia Optima needed a software update that was covered by a recall. I waited several weeks for the dealership to contact me once the update was available. During the waiting period …

Read full complaint

In September of 2025, my radio and back up camera stopped working. I contacted Hayward Kia and was informed by staff member, Eraca Craig, that my 2015 Kia Optima needed a software update that was covered by a recall. I waited several weeks for the dealership to contact me once the update was available. During the waiting period my car's battery started to drain intermittently. I had to have the battery recharged multiple times by AAA. The battery would stay charged for a few days, maybe a week, then I'd experience the same issue. AAA towed my car to Kia Hayward on October 3, 2025. They charged my battery and kept my car over night to see if the battery would stay charged, it did not. Eraca told me that the AC Delco battery I purchased on January 16, 2025 was not "compatible" with my car. She recommended a factory Kia battery which I purchased on October 7, 2025. By November 1, my Kia battery had drained. AAA recharged the battery and it held a charge until November 25, 2025. When I took my car to Kia on November 11, 2025 for the software update, I was told that the update did not apply to my malfunctioning radio and camera therefore I needed to replace the entire unit for $4,080.49. On December 6, 2025 I had a diagnosis performed on my car, it reported codes C1102, B1102, B1112, and P000. C1102 indicates an issue with the HECU. My 2015 Kia Optima has had three recalls related to the HECU (#SC284,#SC212, &#SC197). On December 8, 2025 I made a request, via e-mail, to Eraca Craig that my HECU be inspected for leaks and to have the HECU fuse replaced. I understand that these services were recorded as performed in the past, but I need them performed again because I'm not satisfied that Kia has remedied the situation. I've also filed complaints with the Kia Customer Care Center. My case numbers are #25697367 and #25723089.

NHTSA ODI #11703872

Mileage unknown · Dec 3, 2025
Electrical SystemEngine

The incident took place on Sunday, December 30th. I was driving to pick up my children from their father and on our way home my car stopped accelerating entirely. This had only happen one other time a few days prior. I was in a gas station parking lot and initially when I turned my car on and went to put it into drive it wouldn’…

Read full complaint

The incident took place on Sunday, December 30th. I was driving to pick up my children from their father and on our way home my car stopped accelerating entirely. This had only happen one other time a few days prior. I was in a gas station parking lot and initially when I turned my car on and went to put it into drive it wouldn’t accelerate. I thought that was odd so I did the only thing I knew how to, I checked my oil levels. Levels were full and no other issues were there. The check engine light had popped up when I turned my car back on but my car did accelerate so I thought nothing of it. I took my car to auto zone for a diagnostic and they told me my “B cam shaft” sensor needed to be moved and that could be causing the engine light to come on and ticking in my motor. I called a few shops getting quotes and eventually was forced to tow to the closest shop to me after my car refused to start overall. They replaced the battery and the b cam shaft censors and still were unable to get the car started. They told me 3 recalls were open on my car, including the motor and to have it towed to Kia for a full replacement. After calling Kia to have the repairs done, they refused me service based on a previous owner not handling prior recalls.

NHTSA ODI #11702641

Mileage unknown · Oct 14, 2025
Electrical SystemEngine

All recalls were not done false input information they never fixed engine bearing recall I’m getting a consultant to handle all the false information being provided by Kia Federico in woodriver

NHTSA ODI #11693463

Official recalls

4

23V652000 · Service Brakes, Hydraulic:antilock/traction Control/electronic Limited Slip:control Unit/module

Sep 25, 2023

Kia America, Inc. (Kia) is recalling certain 2010-2019 Borrego, 2014-2016 Cadenza, 2010-2013 Forte, Forte Koup, Sportage, 2015-2018 K900, 2011-2015 Optima, 2011-2013 Optima Hybrid, Soul, 2012-2017 Rio, 2011-2014 Sorento, and 2010-2011 Rondo vehicles. The Hydraulic Electronic Control Unit (HECU) may experience an electrical short, which can result in an engine compartment fire while parked or driving.

Consequence & remedy

Consequence: An engine compartment fire while parked or driving can increase the risk of injury.

Remedy: Owners are advised to park outside and away from structures until the recall repair is complete. Dealers will replace the HECU fuse, free of charge. Interim notification letters, notifying owners of the safety risk, were mailed November 14, 2023. Owner notification letters were mailed March 29, 2024 through June 18, 2024. Owners may contact Kia customer service at 1-800-333-4542. Kia's number for this recall is SC284.

21V331000 · Service Brakes, Hydraulic:antilock/traction Control/electronic Limited Slip:control Unit/module

May 10, 2021

Kia Motors America (Kia) is recalling certain 2013-2015 Optima and 2014-2015 Sorento vehicles previously recalled under recall 20V-519. Brake fluid may leak inside the Hydraulic Electronic Control Unit (HECU), possibly resulting in an electrical short.

Consequence & remedy

Consequence: An electrical short in the HECU increases the risk of a fire while parked or driving.

Remedy: Owners are advised to park outside and away from other vehicles and structures until the recall repair is completed. Dealers will install a new multi-fuse, and inspect the HECU for leaks, replacing the HECU if necessary, free of charge. Owner notification letters were mailed on July 2, 2021. This recall supersedes previous NHTSA recall number 20V-519. Owners may contact Kia customer service at 1-800-333-4542. Kia's number for this recall is SC212.

20V519000 · Service Brakes, Hydraulic:antilock/traction Control/electronic Limited Slip:control Unit/module

Aug 27, 2020

Kia Motors America (Kia) is recalling certain 2013-2015 Optima and 2014-2015 Sorento vehicles. Brake fluid may leak inside the Hydraulic Electronic Control Unit (HECU), possibly resulting in an electrical short.

Consequence & remedy

Consequence: If the HECU short circuits, there is an increased risk of an engine compartment fire.

Remedy: Kia will notify owners, and dealers will inspect the HECU for leaking brake fluid and replace the HECU if necessary, free of charge. Owners are advised to park outside and away from other vehicles and structures until the recall repair is completed. The recall began October 20, 2020. Owners may contact Kia customer service at 1-800-333-4542. Kia's number for this recall is SC197.

18V907000 · Engine; Fuel System, Gasoline:delivery:hoses, Lines/piping, And Fittings

Dec 19, 2018

Kia Motors America (Kia) is recalling certain 2011-2017 Optima, 2012-2017 Sorento and 2011-2018 Sportage vehicles that previously received an engine replacement under recall number 17V-224, warranty, or the Knock Sensor Detection System (KSDS) Product Improvement Campaign. The high pressure fuel pipe that connects to the fuel pump outlet may have been damaged, misaligned or improperly torqued during the engine replacement procedure, possibly causing a fuel leak.

Consequence & remedy

Consequence: A fuel leak in the presence of an ignition source can increase the risk of a fire.

Remedy: Kia has notified owners, and dealers will inspect and replace the fuel pipe, as necessary, free of charge. The recall began January 17, 2019. Owners may contact Kia customer service at 1-800-333-4542. Kia's number for this recall is SC172.

Additional source detail variants (2)

Engine

Kia Motors America (Kia) is recalling certain 2011-2017 Optima, 2012-2017 Sorento and 2011-2018 Sportage vehicles that previously received an engine replacement under recall number 17V-224, warranty, or the Knock Sensor Detection System (KSDS) Product Improvement Campaign. The high pressure fuel pipe that connects to the fuel pump outlet may have been damaged, misaligned or improperly torqued during the engine replacement procedure, possibly causing a fuel leak.

Consequence: A fuel leak in the presence of an ignition source can increase the risk of a fire.

Remedy: Kia has notified owners, and dealers will inspect and replace the fuel pipe, as necessary, free of charge. The recall began January 17, 2019. Owners may contact Kia customer service at 1-800-333-4542. Kia's number for this recall is SC172.

Fuel System, Gasoline:delivery:hoses, Lines/piping, And Fittings

Kia Motors America (Kia) is recalling certain 2011-2017 Optima, 2012-2017 Sorento and 2011-2018 Sportage vehicles that previously received an engine replacement under recall number 17V-224, warranty, or the Knock Sensor Detection System (KSDS) Product Improvement Campaign. The high pressure fuel pipe that connects to the fuel pump outlet may have been damaged, misaligned or improperly torqued during the engine replacement procedure, possibly causing a fuel leak.

Consequence: A fuel leak in the presence of an ignition source can increase the risk of a fire.

Remedy: Kia has notified owners, and dealers will inspect and replace the fuel pipe, as necessary, free of charge. The recall began January 17, 2019. Owners may contact Kia customer service at 1-800-333-4542. Kia's number for this recall is SC172.

Model-level recall history does not show whether a particular VIN is affected or has received a repair. Check a VIN with NHTSA ↗

NHTSA investigations

4

AQ23002 · Hyundai And Kia Abs Module Fires

Opened Nov 17, 2023 · No close date supplied

Status: open (inferred from source dates) · Service Brakes, Hydraulic:antilock/traction Control/electronic Limited Slip:control Unit/module

The Office of Defects Investigation (ODI) has received eight Hyundai Motor America (Hyundai) and eight Kia America, Inc. (Kia) Part 573 Recall Reports between 2016 and 2023. The combined 16 safety recalls all involve the antilock braking system (ABS) modules or Hydraulic Electronic Control Units (HECU) manufactured by the equipment supplier Mando. The Part 573 Recall Reports contain varying defect descriptions and differing remedy descriptions for the same or similar equipment supplied by Mando. Safety recalls included in this Audit Query (AQ) review include: Hyundai recalls 20V-520, 20V-543, 21V-161, 21V-160, 21V-303, 22V-056, 22V-810, and 23V-651. Kia recalls 16V-815, 20V-518, 20V-519, 21V-137, 21V-331, 22V-051, 22V-800, and 23V-652 The purpose of this AQ is to evaluate the timeliness and scoping of Hyundai and Kia’s defect decision making and adherence with reporting requirements; and understand the varying defect descriptions and remedies between these recalls.

DP22003 · Loss Of Motive Power

Opened Sep 12, 2022 · Closed Dec 12, 2023

Status: closed (inferred from source dates) · Engine

The National Highway Traffic Safety Administration (NHTSA) received a letter dated July 13, 2022, petitioning the Agency to initiate a safety defect investigation into loss of motive power allegations attributed to oil drain pan assembly failures on certain Hyundai Motor America, Inc. and Kia America, Inc. vehicles spanning Model Years (MY) 2005-2021. The Petitioners cited examples of complaints indicating that the subject vehicles were experiencing rapid loss of engine oil due to oil drain plug back outs, resulting in loss of motive power and/or catastrophic engine damage. Additional complaints were provided which alleged that the oil drain pans lack sufficient structural integrity and are susceptible to cracking. The petition itself can be reviewed at NHTSA.gov under ODI number 11481745. On September 12, 2022, the Office of Defects Investigation (ODI) opened Defect Petition (DP22-003) to evaluate the Petitioners’ request. The Petitioners have provided additional complaints within four supplemental letters dated January 31, 2023, March 21, 2023, May 23, 2023, and August 4, 2023. ODI’s evaluation included the review and analysis of the complaints and supporting information submitted by the Petitioners, as well as additional complaints submitted directly to NHTSA which referenced either the oil drain plug or a crack in the oil pan. After reviewing the available data, ODI has not identified evidence that would support opening a defect investigation into the oil drain pan assemblies of the subject vehicles. Based on a review of the available information, a loss of motive power resulting from an oil drain plug back out has not occurred between the initial sale of a vehicle and the completion of its first oil change. If during an oil change service, a technician fails to remove the existing drain plug gasket before installing a new gasket, it is likely that a proper seal between the drain plug and the oil pan will not be made. An improper seal between the drain plug and oil pan could lead to the backing out on the drain plug, resulting in the sudden loss of oil while driving. Additionally, the provided examples of oil pan cracks were localized to the immediate vicinity of the oil drain plug and/or appeared to be the result of direct-contact with a tool during servicing.  There is no information to support that a vehicle-based defect exists relating to the oil pan assembly, and instead the documented incidents are related to the failure to follow the proper maintenance procedures during oil change service. In October 2023, Hyundai published a Technical Service Bulletin (TSB) that provided detailed instructions for oil change service on its gasoline powered vehicles, specifically highlighting the need to remove and replace the existing drain plug gasket prior to reinstalling the drain plug. After a thorough review of the material submitted by the petitioner, the information already in NHTSA's possession, and the potential risks to motor vehicle safety implicated by the petitioners' allegations, NHTSA does not believe that a formal investigation is warranted. Therefore, the petition is denied. A Federal Register Notice (FRN) further detailing NHTSA’s reasons for denial of the petition will be published. The reference numbers for the complaints to NHTSA cited by the petitioner can be found in the petition submission documents in the public file for DP22-003. To review those complaints and the additional complaints ODI added to its evaluation which are cited in the Closing Resume ODI Report Identification Number document, go to NHTSA.gov.

DP21003 · Throttle Control System Vulnerabilities

Opened Nov 12, 2021 · Closed Jun 20, 2023

Status: closed (inferred from source dates) · Vehicle Speed Control:throttle

The Office of Defects Investigation (ODI) of the National Highway Traffic Safety Administration (NHTSA) received a petition letter dated October 10, 2021, requesting an investigation of possible defects in the electronic throttle control (ETC) system on certain Kia vehicles resulting in the opening of DP21-003. Accordingly, Model Year (MY) 2005-2016 Kia Optima/K5, MY 2006-2015 Kia Sorento, MY 2007-2016 Hyundai Elantra, MY 2007-2016 Hyundai Santa Fe, MY 2006-2015 Hyundai Sonatas are all part of the subject population. The petition was originally filed as a Vehicle Owner Questionnaire that can be reviewed at NHTSA.gov under reference (ODI) number 11439675.On November 12, 2021, ODI opened Defect Petition DP21-003 to evaluate the petitioner?s request. ODI performed trend analyses of the VOQs related to vehicle speed control issues for all the subject vehicles and found that none of the 52 Model/Model Year Hyundai/Kia vehicles demonstrated any actionable trend that warranted an investigation.Petitioners submitted 1119 VOQs and non-VOQ cases in which sudden uncommanded acceleration (SUA) or loss of motive power (LOMP) incidents were alleged.For the 1119 reports, 220 were incidents involving crashes, from which 69 subject Hyundai-Kia vehicles were inspected by Hyundai/Kia dealer technicians, Hyundai/Kia engineers, and/or third-party representatives.ODI found the inspections identified no vehicle defects related to the ETC system.Of the 220 crash-involved reports, 13 Event Data Recorder (EDR) records were downloaded successfully and 11 of those indicated driver error: (i.e.) pedal misapplication.A condition where the accelerator pedal is mistakenly applied instead of the brake pedal when the driver wants to stop the vehicle.In addition, ODI reviewed a scientific journal paper published in Forensic Science International in 2016 by Mr. Park et al ., as well as related test videos. ODI does not believe there is any evidence of uncontrollable SUA occurrences in any of the tests reviewed. NHTSA's Office of Vehicle Safety Compliance (OVSC) reviewed the allegations regarding the potential noncompliance with Federal Motor Vehicle Safety Standard No. 124.Based on the information provided, the Agency concludes there is insufficient information for us to determine if a possible non-compliance exists.Finally, both Hyundai and Kia informed ODI that all their vehicles manufactured after 2012 were equipped with an ETC management system, in which the engine speed will go to idle when the system sees signals from both the brake pedal and accelerator pedal at the same time; this is commonly known as the brake-throttle override system.After thoroughly assessing the material submitted by the petitioner, information already in NHTSA's possession, information submitted by Hyundai and Kia in response to an Information Request letter, and the potential risks to safety implicated by the petitioner's allegation, NHTSA does not believe that a formal investigation is warranted. After full consideration of appropriate factors, the petition is denied. A Federal Register Notice (FRN) further detailing NHTSA?s reasons for denial of the petition will be published.

EA19001 · Electrical Overstress

Opened Apr 19, 2019 · Closed Sep 19, 2024

Status: closed (inferred from source dates) · Air Bags: Air Bag/restraint Control Module

The Office of Defects Investigation (ODI) opened this investigation to determine if the failure of airbags to deploy during severe crashes, in certain vehicles, was the result of a safety related defect.  During the investigation a complex failure was studied that can result in non-deployment of subject vehicle air bags and other restraint system devices in severe crash events. The subject vehicles may be equipped with an airbag control unit (ACU) for the supplemental restraint system (SRS) Electronic Control Unit (ECU) manufactured by ZF-TRW.  The ECU receives signals from crash sensors mounted in the vehicle and deploys the vehicle air bags and seat belt pretensioners in accordance with manufacturer design specifications.  The ECU in the subject vehicles contains a model DS84 application-specific integrated circuit (ASIC) which controls the communication of the crash sensor signal, firing commands (i.e., when to deploy the airbag(s) and/or pretensioners), and fault information (e.g., diagnostic trouble codes). In September 2016, FCA announced recall 16V-668 for certain model year (MY) 2010 to 2014 Chrysler, Dodge and Jeep products manufactured with the subject ZF-TRW ACU.  In this recall, FCA discussed an EOS condition that resulted in a failure of the subject DS84 ASIC, which caused air bag non-deployment.  FCA noted that the defect condition had only been observed in vehicles equipped with sensor harnessing routed across the front of the vehicle.  Other FCA vehicles that also used the subject ACU, but were not equipped with cross-car harnessing, had not experienced EOS failures, despite similar time in service. During the course of this investigation, ODI sent two separate Information Request (IR) letters to six vehicle manufactures (including FCA, Hyundai, Honda, Kia, Mitsubishi, and Toyota) and one IR letter to ZF-TRW.  These IR letters resulted in ODI receiving comprehensive data from these manufacturers and suppliers. Studies of this data found that the DS84 ASIC does not have sufficient protection against negative electrical transients or electrical overstress (“EOS”) that can be generated in certain severe crashes.  An electrical transient occurs when the electrical power supplied to a circuit changes momentarily over a short duration of time.   In these severe crash cases, the crash sensors and other powered wiring can be damaged and short circuited so as to create a negative electrical transient of sufficient intensity and duration (that are outside the vehicle manufacturer's specification) to damage the ASIC before the restraint device deployment signal is received by the SRS ECU.  This damaged signal can lead to incomplete or nondeployment of the air bags and/or pretensioners.  Airbag non-deployment and/or lack of pretensioner operation can increase the risk or severity of injury in a crash.A total of 8 fatalities and 14 injuries were associated with known EOS events. The common element in all investigated manufacturers vehicles is the SRS ECU containing a DS84 ASIC manufactured by ZF-TRW.  The risk associated with the ASIC is equally shared among all OEMS involved in the investigation.  The actual real-world risk can be mitigated by other factors which were assessed by ODI during this investigation. The first mitigating factor involves protections built into the ACU design which protect the DS84 ASIC from damage.  There are multiple strategies and levels of protection employed by different OEMs that provide effective EOS mitigation.  The two most common strategies at the ACU level are circuit protection diodes on the remote senor signal lines, and current limiting resistors that protect critical components. The second mitigating factor is found at the vehicle level and involves the location and routing of the wires leading from the crash sensors to the SRS ECU.  If the wires are well protected in a crash and are not routed with other power wires carrying large currents, the risk for an EOS event is significantly reduced or eliminated. These design specific factors combine to produce a spectrum of risk for the vehicles equipped with ACUs using the DS84 ASIC.  Given the many of years of field exposure, it is possible to divide the subject population into two groups; vehicles which have experienced EOS events, and vehicles which have not experienced EOS field events. Four of the six OEMs involved in this investigation have experienced EOS field events on at least one of their models equipped with a DS84 ASIC.  All vehicle models (including the Toyota models identified in the Failure Report Summary of the opening resume for this investigation) with field events have been recalled.  In an abundance of caution, ODI kept this investigation open five years to monitor field performance and did not identify any field events on vehicles not included in existing safety recalls. Given the spectrum of risk identified in this investigation and that all vehicles with a demonstrated unreasonable risk have been recalled, ODI is closing this investigation. ODI is closing this investigation with the following manufacturer safety recalls: 16V-668, 18E-043, 18V-137, 18V-363, and 20V-024.  With the recall actions taken by the subject vehicle and equipment manufacturers, this investigation is closed. The closing of this investigation does not constitute a finding by NHTSA that a safety-related defect does not exists on other model or model year vehicles outside of the recall scopes. The agency reserves the right to take further action if warranted by the circumstances.