2009 Mercedes-Benz C300 Problems

What owners report

Owners of this model year most often write about two clusters of problems: the electronic steering lock/ignition assembly that leaves the car unable to start, and rear subframe corrosion that shows up as swaying, clunking or poor braking stability. A separate, older group of complaints covers melted rear taillight connectors, while air bag warnings and the open Takata inflator campaigns appear across the sample. Most reports arrive between roughly 60,000 and 140,000 miles.

1. 1
   Steering

   Car won't start, steering locked (ignition/steering lock)

   • 152 complaints (26%)
   • median 78,008 mi at 7.2 yrs old (129 state mileage)
   • owner-quoted repair $1,231 (median of 56 quotes)
   • filed 2010–2025

   Owners describe turning the key and getting nothing — no crank, no dash lights — with the steering wheel locked and a message telling them to remove the key. Many say the car had started normally minutes earlier and had to be towed; some report intermittent no-starts over weeks before it became permanent. Complaints say dealers or independent shops diagnosed the electronic ignition switch and/or electronic steering lock and replaced the assembly, often at owner expense. Mostly reported between about 45,000 and 140,000 miles, frequently on vehicles parked and restarted after a short stop.

   Recall 17V177000Recall 22V168000

   What to check: Ask for service records showing whether the ignition switch or steering lock assembly has already been replaced, and try several cold starts during the test drive, including a restart after a short shutdown. A car that intermittently refuses to crank is worth having inspected before purchase.

   2 excerpts from owner complaints in NHTSA records

   “Car was parked by side walk next to my house. Inserted the key in the ignition and turned it. The car did not start, and the steering wheel was locked. No lights flashed on the dashboard. Car had to be towed on truck bed since it's rear-wheel drive. Dealer told me it's the ignition switch lock cylinder. Cost $1500 to fix. This is a manufacturer's defect. Not fair.”

   NHTSA complaint #11372335, filed 2020-10, 55,000 miles

   “My car every so often won?t start battery is good starter is good just does nothing happened over 10x had it towed to 5 mechanics shops and mercedes can?t diagnose problem because after a day maybe two sometimes 4 or 5 the car will just start up on its own and then a few weeks or months we go through it all over again researched and other mercedes C300 drivers have the same problem for months and its the steering lock module.”

   NHTSA complaint #11326438, filed 2020-05, 85,000 miles
2. 2
   Body and structure

   Rear subframe rusted or cracked

   Mentioned in 15 of 60 sampled complaints

   Complaints describe swaying or fishtailing at speed, clunking from the rear over bumps, and pulling or instability when braking. On inspection, shops found the rear subframe heavily rusted, cracked or broken, in some cases with the lower control arms contacting the fuel tank. Owners report the fix is subframe replacement, quoted at independent shops and dealers, and several mention the car was towed in. Typically reported from around 60,000 miles upward, with many in the 80,000-140,000 mile range; some owners say the car was garaged and not driven in bad weather.

   2 related service bulletins

   What to check: Have the car put on a lift and inspect the rear subframe and its mounts for rust, flaking metal or cracks, especially near the control arm brackets; service bulletins describe corrosion of the rear axle carrier under moisture and road-salt conditions.

   2 excerpts from owner complaints in NHTSA records

   “Bought C300 2009 4 matic sep. 2017 used from a dealer. Carfax indicates getting scheduled service from dealer and it does not show problems with the car. It has now 90k mileage. Lately, I started hearing some noise at the back whenever I hit a small bump, so I decided to bring it to the Mercedes-Benz dealer and have it checked last july 21, 2020. They found out that the rear subframe is broken because of rust. The estimated repair cost is $6,000. …”

   NHTSA complaint #11343806, filed 2020-08, 90,000 miles

   “On my 2009 mercedes C300, the vehicle pulled significantly when the brakes were applied. The repair shop I use checked the braking system and found no issues. They then discovered a rear sub-frame issue. The entire rear sub-frame was rotted out on my 2009 mercedes C300.the vehicle had less than 79k miles on it, did not got out in bad weather and was garaged. I contacted my local mercedes dealer and they showed no interest in addressing the problem under any type of defect resolution issue. …”

   NHTSA complaint #11298344, filed 2020-01, 78,780 miles
3. 3
   Air bags

   Air bag and SRS warning lights

   • 178 complaints (31%)
   • median 74,991 mi at 8.0 yrs old (47 state mileage)
   • 15 mention a crash, fire or injury
   • filed 2010–2026

   Complaints describe the SRS or air bag warning light staying on, sometimes alongside a check engine light, with dealers diagnosing seat-side sensors, pelvis air bags or the air bag control unit. Some owners were told the vehicle was covered by an inflator recall but that parts were not yet available. Others report waiting on replacement parts after recall notices. Spread from about 35,000 to 100,000 miles in this sample, often appearing without any event or impact.

   Recall 16V363000Recall 15V711000Recall 18V043000Recall 17V017000Recall 16V081000

   What to check: Confirm with a dealer, using the VIN, whether the open air bag inflator and control unit recalls have been done, and check that no SRS warning is lit with the engine running.

   2 excerpts from owner complaints in NHTSA records

   “Takata recall- I have two recalls that are both dangerous and not being addressed. The first recall was feb 2016 and the second one in may 2016. I keep getting told there is not a fix ready but ther is a possible risk of injury or death if the airbags deploy. Considering the airbags are a safety feature this is counter intuitive.”

   NHTSA complaint #10967067, filed 2017-03, 36,500 miles

   “Takata recall.. My air bag light remains on and I fear that they are not working. Also, my car will not restart after stopping at a store. In reading the comments in a recent forum, I am not the only mercedes benz owner having this problem. Based on the comments the issue is with the steering column (eis/els) and it is a manufacturing defect. The dealer also verified that this is a common problem with mercedes and the cost to repair it is $2100.00 upward.”

   NHTSA complaint #10887677, filed 2016-07, 100,000 miles
4. 4
   Exterior lighting

   Rear taillight wiring and connector melting

   • 83 complaints (14%)
   • median 59,000 mi at 5.1 yrs old (70 state mileage)
   • 14 mention a crash, fire or injury
   • owner-quoted repair $600 (median of 6 quotes)
   • filed 2011–2026

   Owners report dash warnings for taillight, brake light, turn signal or reverse light failures, and on inspection find the bulb holder wiring insulation and connector melted or burnt. Several say a new rear light assembly or harness was needed, and a few describe smoke or an odor from the housing. Complaints say dealers treated it as a known pattern but charged for the repair. Reported from roughly 39,000 to 75,000 miles in this sample, often noticed after a bulb-out warning.

   Recall 14V177000

   What to check: Check that all rear lamps work and pull the rear bulb carriers to look for browned or melted plastic and wiring; ask whether the 14V177000 tail light recall was completed for this vehicle.

   2 excerpts from owner complaints in NHTSA records

   “Driving on highway, noticed that when I use my left turn signal it was flickering fast on the dash board, then warning message appeared on dash, check turn signal, check brake light, check fog lamp. When I got home, check all bulbs on the left rear light assembly, all bulbs are intact. Noticed the brown wire was a little corroded and like a burnt contact on the light assembly. Started the car again, everything is working okay. Now exact same messages appears more than often when im driving the car. …”

   NHTSA complaint #10551735, filed 2013-11, 39,000 miles

   “Wiring harness on rear tail light melted causing the tail light circuit board to stop working ,causing the brake lights ,reverse lights and blinker to stop working.spoke with mercedes benz dealer ship and they told me this was a common problem and that they were not gonna fix it for free and that I would have to pay for the repairs.this is a hazard cause I was driving at night with my kids in the car,when my lights went out.after looking at the melted harness wire this is also a potential fire hazard. …”

   NHTSA complaint #10575278, filed 2014-03, 70,400 miles

Buying note. A pre-purchase inspection on a lift is the key step for this model year: have the rear subframe checked for corrosion and confirm the ignition/steering lock and open air bag recalls have been addressed. Service history showing those repairs already done is worth more than low mileage alone.

Summary written with AI from a sample of 60 NHTSA complaints for this model year (picked at random, with complaints that state a mileage and recent ones taken first), then checked automatically against the source records. Where a problem shows a complaint count, every complaint for this model year was matched with fixed keyword rules (written with AI and tested against the sample), and the mileage, age and repair figures are calculated from those complaints; owners' figures are as stated, not verified. Other counts refer to the sample. The excerpts come from NHTSA's public complaint records and are unverified; capitalisation is normalised, NHTSA staff notes are removed, and shortened text ends with “…”. Something wrong? Request a correction.