2020 Ford Mustang: check engine light

Filed Aug 20, 2026 · Engine, Fuel system · AZ

2020 Ford Mustang with the 2.3L EcoBoost engine. The vehicle has a documented history of coolant loss with no visible external leak, consistent with the known coolant-intrusion defect in Ford's 2.3L EcoBoost engines where coolant leaks internally into the cylinders. The vehicle previously threw a cylinder misfire code (P0301) and now shows a crankshaft/camshaft timing correlation fault (P0017). A scan tool confirmed the exhaust camshaft is approximately 18–19 degrees out of correlation. A new variable valve timing oil control solenoid was installed and did NOT resolve the fault, confirming the problem is mechanical — a worn/stretched timing chain. This wear is consistent with the oil dilution and contamination caused by internal coolant intrusion. The problem has been confirmed by an independent service center via scan data. The vehicle is available for inspection. Warning symptoms included the check engine light, a loud rattle on cold startup, and occasional hard/no-start conditions. This is a safety concern because internal coolant loss can cause overheating, cylinder head cracking, and potential engine failure or fire while driving. Repair cost quoted at approximately $2,000. Mileage approximately 54,400.

Filed Jul 21, 2026 · Engine · NJ

I own a 2020 Ford Mustang EcoBoost with approximately 75,000 miles. My vehicle developed a check engine light with diagnostic codes P0300 (random misfire) and P0301 (cylinder 1 misfire). I also began experiencing white smoke from the exhaust during cold starts. An independent repair shop suspects coolant is entering cylinder 1 due to a possible head gasket failure. They have recommended removing the cylinder head to inspect for cracks, check for warping, pressure test the head, inspect the cylinder walls, and replace the head gasket and related components if no further engine damage is found. The vehicle was properly maintained, and these symptoms appeared unexpectedly.

Filed May 7, 2026 · Electrical, Engine · CA

Check engine light came on, car lost power on highway. Car continues to have the same issue after repairs have been made. Ford App says engine misfire, after every repair. Ford mechanics fix spark plugs, coils, electrical. None of which has fixed the issue of stalling on the highway which poses risk of me the driver and others driving on the highway. The only light that comes on is engine light.

Filed Jul 10, 2025 · Engine · LA

Coolant intrusion into cylinder/cylinders Problem confirmed by a dealer Check engine light, cylinder 1 missfire is when I noticed an issue

Filed Mar 31, 2025 · Engine · TX

On 03.29.25 (Saturday) the car started rough and the check engine light came on. I took it to the mechanic 03.31.25 (Sunday) and they inspected the car and told me that it is either the head gasket or the engine block is cracked because there is coolant intrusion into the cylinders. They asked me to call FORD customer service and ask if there was any way to cover it under warranty as the car only has 64K miles. I was told no, the warranty was 5yrs or 60K whichever came first and the 5 years was October of 2024. They suggested I file a report with the federal safety agency. The vehicle right now is at the mechanic as I try to decide what I would like to do with it. If the engine failed when driving, I don't know what would have happened. There were no other symptoms to the problem prior to the failure. In fact, weeks earlier I had it inspected to see if any maintenance was needed and it got a clean bill of health.

Filed Jan 22, 2025 · Engine · 53,500 miles · FL

The contact owns a 2020 Ford Mustang. The contact stated while driving 55-60 MPH, the check engine warning light illuminated. The vehicle was taken to AutoZone, where the contact was informed that there was no coolant in the vehicle. The contact added coolant to the vehicle; however, the failure persisted. The vehicle was taken to the dealer, where it was diagnosed that the head gasket had failed, causing coolant intrusion into the engine. The dealer determined that the entire long block and the head gasket needed to be replaced. Additionally, the dealer informed the contact that the long block and the head gasket needed to be aligned correctly. The vehicle was not repaired. The manufacturer was notified of the failure and offered to partially cover the cost of the repair. The failure mileage was approximately 53,500.

Filed Nov 7, 2024 · Engine · 86,000 miles · DE

The contact owns a 2020 Ford Mustang. The contact stated while driving 25 MPH, the check engine warning light illuminated. The contact stated that the engine overheated while driving. The contact was able to pull over and the vehicle was towed to the local dealer to be diagnosed. The contact was informed that there was coolant in the combustion chamber, engine block, and cylinder head, and the low-pressure fuel pump had failed. The dealer recommended an engine replacement. The vehicle was not repaired. The vehicle was taken to an independent mechanic who replaced the head gasket, but the failure recurred. The manufacturer was contacted and referred the contact to the federal safety agency Hotline for assistance. The failure mileage was approximately 86,000.

Filed Sep 9, 2024 · Engine · 59,000 miles · FL

The contact owns a 2020 Ford Mustang. The contact stated that the engine overheated while driving at various speeds with the temperature gauge showing that the engine was hot(H). The contact stated that the vehicle hesitated while depressing the accelerator pedal with an engine misfire alert on the Ford App. The vehicle was taken to a dealer where a pressurized test was performed; the test showed no defect with the engine. The contact then took the vehicle to an independent mechanic where the spark plugs, and cabin air filter were replaced, and the fuel system was cleaned. The check engine warning light illuminated soon after the repair. The vehicle was taken back to the dealer where it remained unrepaired. The manufacturer was notified of the failure and a case was filed. The failure mileage was approximately 59,000.

Filed Jul 26, 2024 · Body, Engine · 86,000 miles · SC

The contact owns a 2020 Ford Mustang. The contact stated that the engine warning light was illuminated. The vehicle was taken to the local dealer, where it was diagnosed and determined that the catalytic convertor and active grill shutter assembly needed to be replaced. The vehicle was not repaired. The manufacturer was contacted and referred to the federal safety agency Hotline. The failure mileage was approximately 86,000.

Filed Mar 15, 2024 · Engine · 63,000 miles · NC

The contact owns a 2020 Ford Mustang. The contact stated that while driving at 15 MPH, the accelerator pedal was depressed; however, the vehicle failed to accelerate as intended. The check engine warning light illuminated, and the vehicle was misfiring. Additionally, the vehicle was shaking, and the contact pulled over to the shoulder of the road. The contact turned the vehicle off and restarted the vehicle. The vehicle was driven to the residence. The contact stated that the failure was persistent. The vehicle was taken to the dealer where it was diagnosed with coolant leak into the cylinders and the engine needed to be replaced. The vehicle was not repaired. The manufacturer was made aware of the failure and advised the contact to report the failure to the federal safety agency Hotline. The failure mileage was approximately 63,000.

Filed Mar 13, 2024 · Engine · 66,500 miles · NC

The contact owns a 2020 Ford Mustang. The contact stated that while driving at 15 MPH, the check engine warning light illuminated, and the vehicle lost motive power. The vehicle was taken to a dealer where it was diagnosed that coolant had leaked into the engine, causing misfiring codes and a lack of motive power which resulted in the engine needing to be replaced. The vehicle was not repaired. The manufacturer was notified of the failure. The failure mileage was 66,500.

Filed Oct 4, 2023 · Electrical, Engine · AZ

I hope this letter finds you well. I am writing to bring to your attention some serious safety issues that I have encountered with a 2020 Mustang that I purchased from CarMAX, West Valley on September 24, 2023. Soon after taking possession of the vehicle, I noticed a malfunction with the airbag system. It is disheartening to report that I had to endure a three-day wait to have the necessary repairs carried out. The delay in rectifying this crucial safety feature is highly concerning, as it exposes both the driver and passengers to unnecessary risks. Unfortunately, the problems did not end there. Shortly after the airbag issue was addressed, the engine light illuminated on the dashboard. Despite my efforts to troubleshoot the problem myself, the light remained illuminated, indicating a persisting issue with the engine. Not only did this cause me considerable inconvenience, but it also raised concerns about the overall reliability and safety of the vehicle. The most alarming incident occurred on October 2, 2023, when my car unexpectedly broke down while I was driving on the freeway. This unexpected failure not only posed a significant risk to my safety but also left me traumatically shaken by the experience. I cannot emphasize enough the fear and anxiety I felt as I navigated the dangerous situation caused by the vehicle's sudden malfunction. I am deeply disappointed by the lack of quality control and the subsequent safety hazards that have plagued my 2020 Mustang. As a consumer, I have a reasonable expectation that the vehicle I purchase will be safe and reliable. It is distressing to find myself in a situation where my safety and wellbeing are compromised due to these issues. I have taken my concerns up with CARMAX and I am waiting for a response. It is my hope that they will investigate the matter and take measures to address it. I will not stop fighting for the safety of my family and myself.