Fault code P1731 – a step-by-step guide to diagnosing and fixing it

Error code P1731 is displayed and the check engine light is on - what does this mean?

DTC P1731 is detected by the OBD/EOBD system when there is a problem with the transmission control module or the communication between the engine and transmission control unit. This manufacturer-specific fault code mainly occurs in Honda and Acura vehicles and relates to a fault in the electronic transmission control unit or the internal wiring of the automatic transmission.

What can cause this fault code?

• Defective transmission control module (TCM)
• Damaged wiring between the engine and transmission control unit
• Loose or corroded plug connections on the transmission control module
• Defective transmission sensors (speed sensor, position sensor)
• Faulty transmission valves or solenoid coils
• Low or contaminated transmission fluid
• Internal transmission damage or wear
• Software error in the transmission control unit

What symptoms occur in parallel with error code P1731?

• Shifting problems: The transmission shifts jerkily or irregularly
• Emergency running program: The transmission remains stuck in a gear
• Starting problems: The engine does not start or only starts with difficulty
• Increased fuel consumption: Due to inefficient transmission control
• Unusual noises: Rattling or grinding from the transmission area
• Warning lights: Check engine light and/or transmission warning light illuminated
• Loss of power: Reduced engine power and poor acceleration

How to fix the problem of trouble code P1731?

• Repairing trouble code P1731 requires a systematic diagnosis, as several components may be affected.
• Replace the transmission control module (TCM) and have it reprogrammed if internal defects are detected
• Check all cable connections between the engine and transmission control unit and repair or replace damaged cables
• Clean plug connections on the transmission control module, treat with contact spray and tighten firmly
• Change the transmission fluid completely and replace the filter if it is dirty or low
• Identify and replace defective transmission sensors (speed or position sensors)
• Check transmission valves and solenoid coils in the valve body and replace if necessary
• Have a software update carried out for the transmission control unit to rectify known program errors
• In the event of serious internal transmission damage, carry out a transmission overhaul or replacement