Fault code P0735 – a step-by-step guide to diagnosing and fixing it

Error code P0735 is displayed and the check engine light is on - what does this mean?

DTC P0735 is triggered by the OBD system when the transmission control unit detects a problem with 5th gear in the automatic transmission. This trouble code indicates an incorrect transmission ratio or a faulty function of the fifth gear. For various manufacturers, this error code can also be referred to as "Gear 5 Incorrect Ratio".

What can cause this error code?

• Defective solenoid valves in the transmission control block
• Worn clutches or belts in 5th gear
• Low or contaminated transmission oil level
• Defective speed sensors in the transmission
• Clogged transmission oil filter
• Mechanical wear of the transmission components
• Faulty wiring to the transmission control unit
• Defective transmission control unit (TCM)
• Hydraulic problems in the transmission

What symptoms occur in parallel with fault code P0735?

• Shifting problems: The transmission does not shift into 5th gear or jumps out
• Jerky driving: Uneven running when accelerating or at constant speed
• Increased fuel consumption: Engine runs at higher speeds than normal
• Emergency running program: Transmission gets stuck in the lower gears
• Delayed shifting: Transmission shifts up late or not at all
• Loss of engine power: Reduced acceleration at higher speeds

How can the problem with error code P0735 be rectified?

• Repairing EOBD error code P0735 requires a systematic approach to identify the root cause.
• Change the transmission oil and filter, as contaminated oil is often the cause of shifting problems
• Check the solenoid valves in the transmission control block and have them replaced if defective
• Test the transmission speed sensors and replace defective sensors
• Check the wiring and plug connections to the transmission control unit for damage
• Diagnose transmission control unit and replace or reprogram if necessary
• Measure the hydraulic pressure in the transmission and repair the pump and valves
• Replace clutches and 5th gear bands in the event of mechanical wear
• Carry out a complete transmission overhaul in the event of serious internal damage