Fault code P0771 – a step-by-step guide to diagnosing and fixing it

Error code P0771 is displayed and the check engine light is on - what does this mean?

The OBD system detects a fault in the shift solenoid A of the automatic transmission, which is responsible for shifting into reverse and certain forward gears. This DTC P0771 affects the automatic transmission and can occur with different manufacturers, whereby the specific symptoms can vary depending on the vehicle model.

What can cause this fault code?

• Defective shift solenoid A in the automatic transmission
• Dirty or blocked hydraulic channels
• Damaged wiring harness to the shift solenoid
• Loose or corroded plug connections
• Defective transmission control unit (TCM)
• Contaminated or used transmission oil
• Mechanical wear of the shift valves
• Defective pressure sensors in the transmission
• Overheating of the automatic transmission

What symptoms occur in parallel with fault code P0771?

• Shifting problems: The transmission shifts jerkily or with a delay
• Reverse gear does not work: Reverse gear cannot be engaged
• Transmission remains in emergency mode: The vehicle only drives in one gear
• Increased fuel consumption: Due to inefficient gear changes
• Unusual noises: Rattling or knocking when changing gear
• Transmission overheating: Transmission temperature warning light comes on

How can the problem with error code P0771 be rectified?

• The repair usually requires a systematic diagnosis to identify the exact cause.
• Change the transmission oil and filter, as contaminated oil can block the solenoid valves
• Replace shift solenoid A if it is electrically defective or mechanically blocked
• Check and repair the wiring harness and plug connections to the transmission
• Diagnose transmission control unit (TCM) and replace or reprogram if necessary
• Clean the hydraulic block of the transmission or have it overhauled
• Carry out a complete transmission overhaul if several internal components are damaged