P0755 Generic (SAE)

Shift Solenoid 'B' Malfunction

Updated 2026-10-02 · Transmission

Severity

Medium

Typical repair cost

100 – 1 200 EUR

System

Powertrain

What it means

Shift solenoid B works together with solenoid A to select gears; the on/off pattern of both defines which shift valves move. P0755 sets when the TCM sees an electrical fault in the B circuit or when the gear produced by the commanded pattern does not match the expected ratio. Depending on the design, failure of solenoid B typically leaves the transmission with only two usable gears in limp mode.

Advertisement728 × 90

Symptoms

Only 2nd and 3rd (or similar pair) available, no 1st from standstill
Harsh engagement and jerky shifts
Shift flare followed by bind-up on upshifts
Lack of overdrive, high RPM on the motorway
MIL on, possible P0732/P0733 companion codes

Common causes

Solenoid B coil open, shorted or intermittently failing when hot
Solenoid plunger stuck from debris or varnish
Internal harness insulation hardened and cracked by heat
External connector corroded or pushed-back pin
Low fluid or clogged filter reducing solenoid supply pressure
TCM output driver failure

How to diagnose

Scan the TCM for companion codes and freeze-frame temperature; a fault appearing only above 80 °C fluid temperature points to a heat-sensitive coil or harness.
Measure solenoid B resistance at the transmission connector: typically 10-25 ohms (on/off) or 3-8 ohms (linear) at 20 °C; repeat hot if the fault is intermittent and look for a change greater than 10 %.
Check the circuit from the TCM: continuity under 1 ohm, no short to ground or to the adjacent solenoid wire, 12 V supply present where applicable.
Command solenoid B with the scan tool and observe the current trace on an oscilloscope; a normal trace shows the inductive hump as the plunger moves, a flat trace means it is stuck.
Verify fluid level and filter condition; check line pressure (3.5-5 bar idle, 12-18 bar stall) because low pressure can mimic a solenoid fault.
Replace the solenoid or pack with fluid and filter, clear adaptations and perform the shift adaptation drive.

Frequently asked questions

Why are only two gears available?

The TCM de-energises all solenoids in limp mode. The hydraulic default of most 4- and 5-speed designs is 2nd or 3rd, which gives a drivable compromise.

Does an intermittent P0755 need immediate repair?

Yes. Intermittent heat-related failures become permanent, and every limp-mode event with a flare wears the clutches a little more.