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According to Au7o's analysis of 4,300+ owner reports, the 2009 Mercedes-Benz CLS-Class has 2 documented known issues, with 2 rated critical. The most serious are M272 Balance Shaft Gear Wear and Failure ($2,000-$5,000 repair) and 7G-Tronic Transmission Valve Body Failure ($1,500-$4,000 repair). The most commonly reported issue is M272 Balance Shaft Gear Wear and Failure with 2,500 owner reports. Across all issues with published estimates, repair costs range from $1,500 to $5,000. DIY maintenance guides at au7o.io.
All 2 Known Issues
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Community reported
2,500 owners
On the 2005-2010 Mercedes-Benz CLS-Class, the M272 V6 and M273 V8 engines in early CLS models suffer from a well-documented balance shaft gear failure where the idler gear sprocket wears prematurely due to a manufacturing defect. The worn gear produces a rattling noise on startup and can eventually cause engine timing issues and catastrophic damage if the gear teeth strip completely.
Common Symptoms
Rattling or chattering noise on cold start
Check engine light with timing codes
Rough idle that worsens over time
Metallic debris found in oil
How to Fix
Replace the balance shaft gear, idler gear, and associated chain with the updated Mercedes parts (revised sprocket material). This is a significant repair requiring partial engine disassembly. If caught early before timing is affected, the repair prevents further engine damage.
Owner tips & cautions
WarningThis is the most expensive common failure on the M272/M273 engines. If you hear a rattle on cold start, do not delay — the repair cost doubles if the timing chain jumps.
High Confidence2,500 owner reportsLast reported by owners Sep 2025Reviewed Mar 2026
Community reported
1,800 owners
On the 2005-2014 Mercedes-Benz CLS-Class, the 722.9 7G-Tronic automatic transmission in CLS models suffers from valve body conductor plate failures. The electronic conductor plate controls shift solenoids and develops internal short circuits or loses communication, causing harsh shifting, getting stuck in limp mode, or refusing to shift out of park. This is one of the most common transmission failures on Mercedes vehicles of this era.
Common Symptoms
Harsh or delayed gear shifts
Transmission stuck in limp mode (3rd gear only)
Transmission fault warning on dashboard
Failure to shift out of park intermittently
Erratic shift points
How to Fix
Replace the valve body conductor plate (also called the TCU sleeve or electrical connector plate). The valve body itself may also need replacement if the solenoids are worn. Fluid and filter change should be performed simultaneously with Mercedes-approved ATF.
Owner tips & cautions
TipChange the transmission fluid and filter every 40,000 miles despite Mercedes claiming it is "lifetime fill." This is the single best thing you can do to prevent valve body issues.
What are the most common Mercedes-Benz CLS-Class problems?
According to Au7o's analysis of 4,300+ owner reports, the 2009 Mercedes-Benz CLS-Class has 2 documented issues. The most frequently reported are: M272 Balance Shaft Gear Wear and Failure, 7G-Tronic Transmission Valve Body Failure. Of these, 2 are rated critical and should be addressed promptly.
Is the Mercedes-Benz CLS-Class reliable?
The 2009 Mercedes-Benz CLS-Class has 2 known issues documented across 4,300+ owner reports. 2 issues are rated critical: M272 Balance Shaft Gear Wear and Failure and 7G-Tronic Transmission Valve Body Failure. Prospective buyers should inspect for these issues and factor potential repair costs into their purchase decision. Regular maintenance following the manufacturer's schedule helps prevent many common problems.
How much does it cost to fix common Mercedes-Benz CLS-Class problems?
Repair costs for known Mercedes-Benz CLS-Class issues range from $1,500 to $5,000, depending on the specific problem and whether you choose DIY or professional repair. The most critical issue, M272 Balance Shaft Gear Wear and Failure, typically costs $2,000-$5,000 to repair. Au7o provides step-by-step DIY maintenance guides that can help reduce repair costs.
What is the 2005-2010 Mercedes-Benz CLS-Class M272 Balance Shaft Gear Wear and Failure?
The M272 V6 and M273 V8 engines in early CLS models suffer from a well-documented balance shaft gear failure where the idler gear sprocket wears prematurely due to a manufacturing defect. The worn gear produces a rattling noise on startup and can eventually cause engine timing is… Repairs typically run $2,000-$5,000. Severity: high.
What is the 2005-2014 Mercedes-Benz CLS-Class 7G-Tronic Transmission Valve Body Failure?
The 722.9 7G-Tronic automatic transmission in CLS models suffers from valve body conductor plate failures. The electronic conductor plate controls shift solenoids and develops internal short circuits or loses communication, causing harsh shifting, getting stuck in limp mode, or r… Repairs typically run $1,500-$4,000. Severity: high.
Content on this page was compiled with AI assistance using NHTSA complaints, TSBs, owner reports, and public automotive data. While we strive for accuracy, this information may contain errors. Always verify repair procedures and specifications with your vehicle's service manual or a qualified mechanic.
