Fault code P0733 – a step-by-step guide to diagnosing and fixing it

Error code P0733 is displayed and the check engine light is on - what does this mean?

The OBD system detects a malfunction in third gear of the automatic transmission, whereby an incorrect transmission ratio is detected. This DTC P0733 indicates that the transmission control unit has registered an implausible ratio between input speed and output speed in third gear.

What are the possible causes of this error code?

• Worn clutch disks or brake linings in third gear
• Defective solenoid valves (solenoid valves) in the transmission control block
• Low or contaminated transmission oil level
• Clogged transmission oil filter
• Damaged wiring to the transmission sensors
• Defective speed sensors (input/output speed sensor)
• Mechanical damage to planetary gears or gear wheels
• Faulty transmission control unit (TCM/PCM)
• Loose or corroded plug connections

What symptoms occur in parallel with error code P0733?

• Shifting problems: The transmission does not shift into third gear or jumps out
• Jerking when changing gear: Smooth gear changes, especially when shifting up
• Increased engine speed: Engine revs up without a corresponding increase in speed
• Emergency running program: Transmission remains in a safe gear (usually 2nd or 3rd gear)
• Overheating: Transmission temperature rises abnormally
• Delayed acceleration: Vehicle accelerates sluggishly or not at all in the gear concerned

How can the problem with error code P0733 be rectified?

• The repair requires a systematic approach, as various components can be affected.
• Change the transmission oil and filter: Perform a complete oil change with new ATF oil, replace the transmission filter and set the oil level correctly
• Replace solenoid valves: Locate defective solenoid valves in the transmission control block and replace with new original parts
• Check wiring and plugs: Inspect all electrical connections to the transmission sensors for damage and repair
• Replace speed sensors: Test input and output speed sensors and replace with new sensors if defective
• Program the transmission control unit: Update TCM/PCM software or replace control unit in case of irreparable faults
• Overhaul transmission: In the event of mechanical damage, complete transmission repair with replacement of clutches, belts and planetary gears