What does it mean?
P1757 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Transmission Shift Solenoid 'B' Circuit Malfunction .
Symptoms
- MIL (check engine lamp) on with a transmission warning lamp
- Harsh engagement or a constant firm feel even at light throttle
- Wrong gear selection, or an unexpected downshift on a light throttle cruise
- Limp mode with reduced gear availability after repeated faults
- Transmission temperature climbing faster than normal
Likely causes
- Solenoid B stuck partially open so pressure never falls to the commanded level
- Debris under the solenoid seat preventing a full close
- Worn valve body bore or a leaking separator plate bleeding pressure into the circuit
- Electrical fault such as a short to ground keeping the solenoid partly energised
- Corroded case connector or damaged internal harness altering circuit resistance
- Pressure regulator or line pressure running higher than specification
- Module driver stage fault, checked only after the hydraulic and electrical tests
How to fix it
- Check fluid level and condition, and confirm the specified fluid is in use
- Log commanded and actual pressure or ratio values during a controlled road test
- Fit a pressure gauge and compare readings with specification at idle and under load
- Command shift solenoid B with a scan tool and watch the pressure follow the command
- Measure solenoid resistance and check the drive circuit for a partial short to ground
- Remove the valve body and inspect the solenoid seat, screens and valve bores
- Replace the solenoid or valve body, then verify pressure tracks the command through all gears