Fault code P1861 – a step-by-step guide to diagnosing and fixing it

Error code P1861 is displayed and the check engine light is on - what does this mean?

The DTC P1861 is set by the OBD/EOBD system when a problem is detected with the transmission oil pump or the hydraulic pressure in the automatic transmission. This manufacturer-specific fault code mainly affects the transmission management system and can have different meanings for different vehicle brands.

What causes can this error code have?

• Defective transmission oil pump
• Low transmission oil level
• Clogged transmission oil filter
• Damaged solenoid valve in the transmission
• Defective pressure sensors in the transmission
• Worn seals and leaks
• Electrical problems with the transmission pump
• Defective wiring to the transmission management system
• Blocked hydraulic lines
• Defective transmission control unit

What symptoms occur in parallel with fault code P1861?

• Shifting problems: The automatic transmission shifts jerkily or not at all
• Delayed shifting: Significant delay when changing gear
• Loss of power: Noticeable reduction in engine power
• Emergency running program: The transmission switches to emergency running mode
• Unusual noises: Howling or whirring noises from the transmission
• Overheating: The transmission becomes unusually hot
• Jerking when starting off: The vehicle jerks when starting off or accelerating

How to fix the problem of error code P1861?

• The repair requires a systematic diagnosis of the transmission system.
• Check the transmission oil level and top up to the correct level if necessary, using high-quality ATF oil in accordance with the manufacturer's specifications
• Change the transmission oil filter and replace the entire transmission oil at the same time to remove impurities
• Check the transmission oil pump for mechanical defects and replace completely if worn or damaged
• Test all pressure sensors in the transmission with a diagnostic device and replace defective sensors
• Check the solenoid valves in the transmission individually and replace the affected valves in the event of malfunctions
• Check wiring and plug connections to the transmission management system for damage and repair
• Read out transmission control unit with professional diagnostic software and reprogram or replace if necessary