P0731: Gear 1 Incorrect Ratio
27 vehicles · 12 makes · $100-$12,000 repair
Most Reported On
P0731 is an OBD-II diagnostic trouble code meaning “Gear 1 Incorrect Ratio.” This code means the Transmission/Powertrain Control Module detected an incorrect gear ratio in 1st gear. The module compares input (engine/turbine) speed to output shaft speed; when the car is commanded into 1st but the calculated ratio doesn't match the expected value, P0731 sets. This points to slipping, an incorrect shift, or a hydraulic/mechanical problem rather than just an electrical fault. You may feel slipping, harsh or delayed engagement, or the transmission may go into a limited 'limp' mode. This code is most commonly reported on 2005-2014 Mercedes-Benz CLS-Class (CLS350, CLS500, CLS550, CLS63 AMG), 2017-2023 Mercedes-Benz GLS (GLS450, GLS580), and 2016-2023 Mercedes-Benz Metris (Cargo, Passenger), plus 24 other vehicles, with repair costs ranging from $100 to $12,000.
Common Causes
Typical Repair Cost
Based on 33 documented vehicle-specific issues. Actual cost depends on root cause and vehicle.
Diagnostic Tools
To diagnose P0731, you'll need an OBD-II scanner. Here are our recommendations at every price point.
ANCEL AD310 Classic OBD-II Scanner
by ANCEL
A simple, affordable code reader that reads and clears check engine codes. Great for quick diagnostics on any OBD-II vehicle (1996+).
- Read & clear engine codes
- View freeze frame data
- I/M readiness status
- No batteries or app needed
BlueDriver Pro Bluetooth Scanner
by BlueDriver
Bluetooth OBD-II scanner with a free companion app. Provides enhanced diagnostics, smog readiness, and repair reports sourced from a database of verified fixes.
- Enhanced diagnostics (ABS, SRS, transmission)
- Repair Reports with verified fixes
- Smog check readiness
- Free app (iOS & Android)
LAUNCH CRP123X OBD-II Scanner
by LAUNCH
A professional-grade handheld scanner that reads all four major systems (engine, transmission, ABS, SRS) with live data streaming and graphing.
- Engine, transmission, ABS, SRS diagnostics
- Live data stream & graphing
- AutoVIN for vehicle identification
- Free lifetime updates via Wi-Fi
Autel MaxiCOM MK808S Diagnostic Tool
by Autel
Shop-level diagnostic tablet with bi-directional control, active tests, and full system coverage. Ideal for serious DIYers and small shops.
- All-system diagnostics (25+ modules)
- Bi-directional control & active tests
- Oil reset, EPB, BMS, TPMS, injector coding
- 7-inch touchscreen with Android OS
As an Amazon Associate, we earn from qualifying purchases. Prices are approximate and may vary.
Vehicles Affected (27)
Transfer Case Actuator Motor Failure
Transfer Case Actuator Motor Failure
Transfer Case Failure - xDrive Models E84/F48 X1
xDrive Transfer Case Stress & Fluid Degradation - F98 X4 M / F98 X4 M
xDrive Transfer Case Stress & Fluid Degradation - F97 X3 M / F98 X4 M
Transfer Case Actuator Motor Failure (xDrive AWD System)
xDrive Transfer Case Actuator Motor Failure - E70/F85/F95 X5 M
Transfer Case Actuator Motor Failure (All xDrive Models)
DCT Dual-Clutch Transmission Wear & Judder - F10 M5
SMG Hydraulic Pump and Clutch Actuator Failure
SMG III Hydraulic Pump Failure - E60 M5
Aisin 8-Speed Transmission Jerking
DCT Dual-Clutch Transmission Shudder & Clutch Wear - F82/F83 M4
10R80 (10-speed) Harsh/Delayed Shifts and Shudder (Software/Valve Body Related)
6R80 6-Speed Automatic Harsh 1-2 Upshift / Erratic Shifting and Lead-Frame Solenoid Body Failure
10R80 10-speed transmission harsh/erratic shifting and torque-converter shudder
2004 545RFE Intermittent Low-Line-Pressure or Gear-Ratio DTCs — Check TCM Build Date
Internal Radiator Transmission-Cooler Failure Cross-Contaminating ATF and Coolant ('Pink Milkshake')
W5A580 (NAG1) 5-Speed Automatic Limp Mode and Harsh Shift from Conductor-Plate Speed Sensors and Fluid Contamination
7G-Tronic Transmission Valve Body Failure
9G-Tronic Harsh Shift
Harsh Shifting and Delayed Engagement in 7G-Tronic Transmission
722.6 5G-Tronic conductor plate failure (limp mode, stuck in 2nd gear)
FAQ
What does P0731 mean?
P0731 stands for "Gear 1 Incorrect Ratio." This code means the Transmission/Powertrain Control Module detected an incorrect gear ratio in 1st gear. The module compares input (engine/turbine) speed to output shaft speed; when the car is commanded into 1st but the calculated ratio doesn't match the expected value, P0731 sets. This points to slipping, an incorrect shift, or a hydraulic/mechanical problem rather than just an electrical fault. You may feel slipping, harsh or delayed engagement, or the transmission may go into a limited 'limp' mode.
What are the most common causes of P0731?
The most common causes of P0731 are: Low or degraded/burnt transmission fluid, Slipping clutch packs or worn friction components, Stuck or faulty shift solenoid affecting 1st gear, Internal hydraulic leak / valve body fault, Worn or failing torque converter, Faulty input or output speed sensor, Mechanical wear (planetary gears, bands) inside the transmission. The specific cause varies by vehicle.
How much does it cost to fix P0731?
Repair costs for P0731 range from $100 to $12,000, depending on the vehicle and root cause.
Which vehicles are affected by P0731?
Au7o has documented P0731 across 27 vehicle models from 12 manufacturers: Acura, BMW, Chevrolet, Chrysler, Dodge, Ford, Jeep, Kia, Lincoln, Mercedes-Benz, Nissan, Volkswagen.
Sources (12)
- mediaMB Medic: 722.9 7G-Tronic Valve Body & Conductor Plate Must Read
- manufacturerECU Testing: Mercedes 7G-Tronic TCM conductor plate failure
- ForumBenzWorld: 722.9 7G Will Valve Body Fail cause Clutch Wear/Fail?
- otherCarComplaints: Mercedes 722.9 7G-Tronic Transmission Problems Cause Lawsuit
- manufacturerIscanTech: Mercedes-Benz 7G Transmission Removing Valve Body
- ForumBenzWorld: Problem with the 7G-tronic on my CLS350
- ForumBimmerpost X1 Forum - Transfer case actuator gear / xDrive malfunction discussion
- ForumBimmerpost X3M/X4M Forum - Transfer case fluid service interval discussion for F97/F98
- ForumXoutpost / X3 Forum - DIY Transfer Case Actuator Gear Replacement (BMW X3/X5/X6 xDrive)
- ForumBimmerpost X5M/X6M Forum - Transfer case actuator motor / VTG issues on F85/F86
- ForumXBimmers Forum - Transfer case actuator gear failure and xDrive malfunction threads
- ForumM5Board - DCT fluid change interval / judder and clutch wear discussions for F10 M5
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.