Fault code P0776 – a step-by-step guide to diagnosing and fixing it

Error code P0776 is displayed and the check engine light is on - what does this mean?

The OBD system has detected a fault in the pressure control valve B of the automatic transmission. This DTC P0776 indicates a problem with the shift valve or the hydraulic pressure control circuit, which impairs proper gear shifting.

What can cause this error code?

• Defective pressure control valve B in the transmission valve block
• Contaminated or clogged transmission oil
• Damaged wiring to the transmission control unit
• Defective transmission control unit (TCM)
• Mechanical wear in the valve block
• Loose or corroded plug connections
• Internal leaks in the hydraulic lines
• Clogged transmission oil filter

What symptoms occur in parallel with fault code P0776?

• Shifting problems: The transmission shifts jerkily or with a delay between gears
• Shift lock: Certain gears cannot be engaged or are skipped
• Increased fuel consumption: Consumption increases due to inefficient gear changes
• Emergency program: The transmission switches to safety mode with limited gear selection
• Unusual noises: Rattling or grinding when changing gear
• Engine revving up: The engine revs up without a corresponding increase in speed

How can the problem with error code P0776 be rectified?

• The repair usually requires a systematic approach to the transmission system.
• Change the transmission oil and filter: Perform a complete oil change with original oil and replace the transmission filter to remove contaminants that could block the pressure control valve
• Check wiring and plug connections: Check all electrical connections to the transmission control unit for corrosion, loose contacts or broken wires and repair as necessary
• Remove and clean the valve block: Dismantle the transmission valve block, clean all channels thoroughly and replace the defective pressure control valve B
• Diagnose the transmission control module: Have the TCM tested and programmed with a professional diagnostic tool or replace it if there are internal defects
• Perform hydraulic pressure test: Measure pressures in all transmission circuits and locate internal leaks or blockages in the system
• Complete transmission repair: In the event of serious internal damage, a general overhaul or replacement of the transmission by a specialist workshop is required