Which parts fail
Components named in complaints (battery, alternator, wiring, ignition, instrument cluster, infotainment).
Mileage when the problem started
Owner reports
Selected complaints filed with NHTSA by 2009 Mercury Mariner owners, lightly cleaned up (personal details are redacted by NHTSA).
The contact owns a 2009 Mercury Mariner. The contact stated that the key was hard to insert into the ignition switch. The power steering assist fault message was displayed. The vehicle was taken to an independent mechanic and the contact was informed that the failure was due to the ignition housing. The contact called the local dealer who informed her the power steering was repaired in 2014 under NHTSA Campaign Number 14V284000 (Steering). The vehicle was not diagnosed or repaired. The manufacturer was not contacted. The failure mileage was approximately 198,725.
My SUV was part of a recall due to the electronic power steering failing. My SUV was allegedly repaired by the cheapest of the three available options (computer reset or some such process). I bought my SUV in 2020. The electronic power steering slowly started going out intermittently and then more frequently over time, but is now completely out. The dealer tested my SUV and stated that the entire steering column needs to be replaced. They claim that the problem has nothing to do with the recall, but I don't believe them. My issue is the exact same issue that prompted the recall in the first place. I should not have to pay for a failed recall repair. I think it's possible that the original dealership faked the repair, or simply chose the cheapest (but not proper) option to save themselves time and money. My shoulder is now damaged due to driving without power steering for so long. …
This is an update to the complaint from June- Because I have to compensate manually for the electric power steering, I've aggravated upper back injuries and strained hip muscles I incurred from work. I have to attend physical therapy for those injuries now, but it's useless if my only mode of transportation prolongs my recovery.-- My 2009 Mercury Mariner's steering wheel started locking up 3 months ago, and it's hard to get the steering wheel and the tires to agree on one direction. I looked up the make and model to see if there was a safety recall for it and there was, but my VIN wasn't included in the recall campaign, even though it fits the criteria exactly. ///Ford Motor Company (Ford) is recalling certain model year 2008-2011 Ford Escape and Mercury Mariner vehicles manufactured August 18, 2006, through September 11, 2010. …
Electronic Power Steering System, which was part of a previous recall, and was allegedly fixed, but continues to experience the same loss of power steering. This is a continual problem, meaning that it is not a one time incident. Yes, the vehicle is available for inspection at any time. When the power steering goes out while driving, the steering wheel jerks to one side, and feels like a lock-up. The vehicle is still drivable, but can be dangerous in a situation where attempting to avoid an obstacle, could result in an inability to do so, because the maneuvers are being executed for a vehicle with power steering, so when it goes out, those same corrections will not successfully avoid a collision. The dealership is aware of the problem. …
While traveling approximately 35 MPH, driving in a straight line on a city street in traffic, the ABS abruptly applied the brakes - hard! The ABS light came on and a "check brake system" warning message was displayed. Also, the electrical system shut down and the engine lost power. After about 5 seconds, power was restored and vehicle was able to proceed. This occurred approximately 8 times over a two mile distance. During the last 4 times, the engine died, lost power completely, and needed to be turned off and restarted to continue. This failure was a dangerous safety hazard. Vehicle was towed to albuquerque Lincoln Volvo. The problem was diagnosed as a failed ABS module, 9l8z. The dealer replaced the ABS module with a faultly module. A second ABS module was installed and the vehicle was deemed repaired. The dealer did not return the defective part for analysis.
Tl contact owns a 2009 Mercury Mariner. The contact stated that while driving approximately 10 MPH the oil and battery warning indicators illuminated and the vehicle stalled. The vehicle restarted but the failure recurred on 2 other occasions. The vehicle was not taken to the dealer. The manufacturer was not made aware of the failure. Also, the contact stated that the vehicle would not start after the anti theft device warning indicator intermittently illuminated. The vehicle was not taken to the dealer. The manufacturer was made aware of the failure and advised the contact to have the vehicle towed to the dealer to have the computer reprogrammed. The approximate failure mileage was 87,000. Updated 4/21/15
Tl* the contact owns a 2009 Mercury Mariner. While driving on an incline at an unknown speed, the vehicle suddenly decelerated and would not accelerate when the accelerator pedal was pressed. The service engine light illuminated prior to the failure. The vehicle stalled and was able to be restarted. The vehicle was taken to an independent mechanic where it was diagnosed that the electronic throttle control failed. The vehicle was not repaired. The manufacturer was not notified. The VIN was unavailable. The failure mileage was 118,000.
Problem started in December 2015, and got progressively worse. Engine would not start when ignition switch was turned to the start position. Had to make several attempts at it, and apply downward force on the key until the necessary contact was made. Once started it seemed to run normal. Ford dealer diagnosed the problem as a defective "ignition lock cylinder housing". They replaced it with a new one, part number 9l8z*3511*a. Engine starts normally now. Total cost to me $527.74.
Vehicle suddenly loses power steering assistance while driving. If the ignition key is cycled the power steering assist May function again. The affected component was determined to be the power steering control module (pscm) within the steering column. A recall was issued for this in 2014, however only the software was updated when the vehicle was brought in for repair. The malfunctioning components were not replaced and the issue has returned.
While in motion the car will stall causing me to pull off to the side of the road, turn the car off, then back on in order for it to work again. This happens every 10-15 miles and its really unsafe! I believe it is a defective throttle body and needs to be fixed asap before I can continue driving it.
Electrical complaints in other Mariner years
Frequently asked questions
How common are electrical problems on the 2009 Mercury Mariner?
NHTSA has 22 complaints about the electrical system of the 2009 Mercury Mariner, 7% of the model year's 315 complaints. The component named most often is ignition (1 mentions).
Is there a recall for 2009 Mercury Mariner electrical problems?
No. NHTSA lists no electrical system recall for the 2009 Mercury Mariner, though it has 1 recall for other components. If the problem is widespread, a repair may still be covered by an extended warranty or a manufacturer service bulletin — ask a dealer.
At what mileage do 2009 Mercury Mariner electrical problems start?
Half of the complaints with a recorded mileage happened before about 98,000 miles, and 7% before 25,000 miles.
Is it dangerous?
Owners linked 0 crashes, 0 fires and 1 injury to electrical system problems on this model year. If you notice symptoms, have the car checked before driving further.
Source: U.S. National Highway Traffic Safety Administration (NHTSA) — owner complaints through October 20, 2026, recalls and defect investigations; fuel economy from the EPA. Complaints are unverified reports and are not proof of a defect. How we rate model years.