Fault codeP0977

MODERATE

Shift Solenoid B Control Circuit High

What this code means

Shift Solenoid B Control Circuit High.

P0977 is a generic code: it means the same thing on every make. P0977 belongs to family P09xx — Transmission and controls. Its page explains how to read a code and groups all its codes by part.

Type of fault

The control unit reads a voltage on this circuit above its expected range. Usual causes: a broken wire or a poor ground, a short to a supply voltage, or the component itself. As with a low signal, check the wiring and connector before the part.

Gearbox shift solenoid

Shift solenoids are electric valves on the gearbox's valve body that direct fluid to the clutches to select each gear. The control unit switches them on and off and checks their circuit.

What you notice

One or more gears missing, harsh or late shifts, a gearbox in limp mode, often blocked in third or fourth gear.

How to check it

Check the fluid level and condition, then the gearbox connector: oil can creep into it and corrode the pins. Measuring the solenoid's resistance through the connector tells a wiring fault from a solenoid fault. Inside the gearbox, the repair requires removing the sump.

What to do

Have it checked this week. The car remains usable, but the fault will not clear itself and will fail the roadworthiness test.

Clearing a code switches the light off but repairs nothing: if the fault remains, the code comes back. Clearing a fault code yourself →

How to read this code

PPowertrain
0standardised code
9Transmission and controls
77P0977