What are the common causes of P277F?

A worn or slipping clutch B pack. Low transmission fluid pressure at clutch B. A sticking shift valve feeding clutch B. Worn internal transmission components letting clutch B drop out.

Read clutch B apply and slip data on a scan tool. Check transmission fluid level and condition. Test line pressure at the clutch B circuit. Inspect the clutch B pack for wear. Overhaul the transmission if the clutch B pack is worn. Clear the code and retest.

P277F

Clutch B Unexpected Mechanical Gear Disengagement

System: Transmission (P code)
Lamp: Check Engine Light
Category: Powertrain - Transmission

What it means

P277F means Clutch B Unexpected Mechanical Gear Disengagement.

Check these first

A worn or slipping clutch B pack
Low transmission fluid pressure at clutch B
A sticking shift valve feeding clutch B
Worn internal transmission components letting clutch B drop out

What to do next

Read clutch B apply and slip data on a scan tool
Check transmission fluid level and condition
Test line pressure at the clutch B circuit
Inspect the clutch B pack for wear
Overhaul the transmission if the clutch B pack is worn
Clear the code and retest

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Updated

Generic SAE J2012 definition. Last updated 2026-10-10.