Common problems with Mercedes-Benz 722.9 mechatronic

722.9 solenoids

Y3/8Y1 WORKING PRESSURE CONTROL SOLENOID (black)
Y3/8Y2 K1 CLUTCH SOLENOID (blue)
Y3/8Y3 K2 CLUTCH SOLENOID (black)
Y3/8Y4 K3 CLUTCH SOLENOID (black)
Y3/8Y5 B1 BRAKE CLUTCH SOLENOID (black)
Y3/8Y6 B2 BRAKE CLUTCH SOLENOID (blue)
Y3/8Y7 B3 BRAKE CLUTCH SOLENOID  (blue)
Y3/8Y8 TCC LOCKUP SOLENOID KÜB (blue)
Y3/8S1 SELECTION RANGE SENSOR

Y3/8N1 TURBINE SPEED SENSOR monitors turbine speed (input shaft/small ring gear)
Y3/8N2 INTERNAL SPEED SENSOR monitors Ravigneaux planet carrier speed (ring gear of rear planetary gear set)

Y3/8N3 OUTPUT SPEED SENSOR
Y3/8N4 FULLY INTEGRATED TRANSMISSION CONTROL

 
Function of Solenoids in the Transmission

The solenoids in the transmission control gear engagement, regulate the torque converter lockup clutch, and monitor hydraulic pressure to prevent overloading of the transmission components, ensuring smooth gear shifts.

In the Mercedes-Benz 722.9 7G-Tronic automatic transmission, a common issue arises with the blue KÜB/TCC solenoid, that controls the operation of the torque converter lockup clutch. Although diagnostic trouble codes may not always appear, symptoms like shuddering and fluctuating RPMs can occur. We recommend replacing this solenoid when replacing the torque converter. A version with a black cap is also available.

The control module contains internal speed sensors that monitor the transmission's operation. A fault in these sensors may cause inaccurate data transfer between the transmission and engine.

Common Symptoms of Control Module Issues
Failure to engage gears: The transmission does not shift into forward or reverse.
Limp Mode: The vehicle enters emergency mode, often limiting operation to 2nd or 3rd gear.
Irregular shifting: The transmission shifts unevenly or with delays.
Check Engine Light: The dashboard displays a warning light linked to transmission issues.
Speedometer malfunction: Speedometer readings may be inaccurate or not function at all.

 
Common Diagnostic Trouble Codes

  • P0717 Input/Turbine Speed Sensor A Circuit No Signal
    Missing signal from the input shaft speed sensor. The control module cannot detect input shaft rotation, affecting gear engagement.
  • P0793 Intermediate Shaft Speed Sensor A Circuit No Signal
    Fault in the output shaft speed sensor. Incorrect speed data can cause gear engagement problems.
  • P0720 Output Speed Sensor Circuit Malfunction DTC
    Fault in the output shaft speed sensor circuit, often indicating a control module issue.
  • P0730 Incorrect Gear Ratio
    The transmission cannot detect the correct gear.
  • P2767 Input/Turbine Speed Sensor B Circuit No Signal
    Torque converter speed sensor failure, potentially causing power loss and transmission malfunction.
  • P2711 Unexpected mechanical gear disengagement
    Gear engagement failed, often linked to control module or hydraulic component issues.
  • P2200–P2204
    Multiple sensor signals are missing or incorrect, possibly due to electrical issues in the control module or its connections.
  • P0750 Shift Solenoid A Malfunction
  • P0755 Shift Solenoid B Malfunction
  • P0760 Shift Solenoid C Malfunction
  • P2714 Pressure Control Solenoid D Perf/Off
  • P0894 Transmission Component Slipping

 
Suggested Repairs

Control Module Replacement or Repair
For speed sensor issues, we recommend replacing the entire control module. For DIY repairers, we offer input speed sensors, output speed sensor and tool for removing the sensors. Replacing these sensors requires soldering and electronics expertise.

Transmission Oil Change
Regular oil changes can prevent solenoid clogging and reduce wear. We offer a complete oil change kit with red oils or with blue oils.