Fault code P0720 – a step-by-step guide to diagnosing and fixing it

Error code P0720 is displayed and the check engine light is on - what does this mean?

DTC P0720 is triggered by the OBD/EOBD system when a problem is detected with the transmission's output speed sensor. This error code occurs when the control unit receives an implausible or missing signal from the sensor that monitors the speed of the transmission output shaft.

What can cause this error code?

• Defective output speed sensor of the transmission
• Damaged or corroded sensor cable
• Loose or dirty plug connections
• Defective wiring to the transmission control unit
• Mechanical problems on the transmission output shaft
• Worn or damaged sensor wheels
• Faulty transmission control unit (TCM)
• Metal chips or dirt on the sensor

What symptoms occur in parallel with fault code P0720?

• Shifting problems: The transmission shifts irregularly or jerkily between gears
• Blocked gears: Individual gears can no longer be engaged or the transmission remains stuck in a gear
• Increased fuel consumption: The engine operates inefficiently due to incorrect transmission information
• Jerking when driving: Noticeable vibrations or jerking while driving
• Emergency running program: The transmission switches to emergency running mode with limited functionality
• Starting problems: In rare cases, the vehicle is unable to start

How can the problem with error code P0720 be rectified?

• The repair requires a systematic diagnosis, as various components may be affected.
• Replace the sensor: Locate the defective output speed sensor, remove it and replace it with a new original part, ensuring correct installation and tightening torques
• Check and repair the wiring: Check all cables from the sensor to the control unit for damage, breaks or corrosion and replace or repair defective cables
• Clean plug connections: Dismantle all plugs on the sensor and control unit, clean with contact spray and reconnect firmly
• Change the transmission oil: Replace the transmission oil and filter to remove metal shavings and dirt that could affect the sensor
• Control unit diagnostics: Check the transmission control unit (TCM) using professional diagnostic technology and have it replaced or reprogrammed if defective
• Mechanical repair: In the event of mechanical transmission damage, visit a specialist workshop to repair or replace the output shaft or sensor wheels