P0718 on Mercedes-Benz: How to Diagnose & Fix
Input/Turbine Speed Sensor Circuit Intermittent
1 Mercedes-Benz model · 1 documented issue · 1 critical · $500-$2,200 repair
P0718 on Mercedes-Benz by model: symptoms, diagnosis and fix
The electronic conductor plate integrated into the 722.9 7-speed automatic's valve body (which houses the internal TCM, speed sensors and shift solenoids) is a widely reported failure on R171 SLKs equipped with the 7G-Tronic. As the plate's internal speed sensors and soldered joints degrade with heat cycling, the transmission drops into limp mode, typically locking into a single forward gear (often 2nd). The condition is temperature-sensitive and commonly appears from roughly 50,000-90,000 miles.
Common Symptoms
- Transmission stuck in gear (often 2nd), won't shift up
- Limp mode / reduced speed limited to ~40 mph
- Harsh or delayed shifts, especially when cold
- Intermittent faults that come and go with temperature
- Speed-sensor fault codes
How to Fix
Replace or rebuild the conductor plate (the revised design), refresh the valve body, and perform a transmission fluid and filter service plus an adaptation reset. Independent specialists offer a cheaper conductor-plate reman as an alternative to Mercedes' full valve-body replacement (roughly $2,000-$3,000 at a dealer). A neglected fluid service accelerates the failure, so periodic 722.9 fluid changes are recommended.
Sources for this issue (3)
P0718 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0718 mean on a Mercedes-Benz?
P0718 stands for "Input/Turbine Speed Sensor Circuit Intermittent." Set when the input/turbine speed sensor signal is intermittent — dropping out or spiking erratically rather than being continuously absent. Usually indicates a marginal sensor or loose wiring. On Mercedes-Benz it is documented across 1 model: SLK/SLC.
What are the most common causes of P0718?
The most common causes of P0718 are: Intermittent open/short in sensor wiring, Loose or corroded connector, Failing input/turbine speed sensor, Debris intermittently affecting signal, Vibration-related harness fault. The specific cause varies by vehicle.
How much does it cost to fix P0718 on a Mercedes-Benz?
Published repair estimates on Mercedes-Benz range from $500 to $2,200 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
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Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.