P0755 - OBD II Trouble Code

Auto Systems and Repair

Shift Solenoid B Malfunction

Our emissions expert has put together the following information about the P0755 fault code. We have also included diagnostic procedures you can take to your repair shop if the mechanic is having difficulty analyzing the code.

OBD II Fault Code

  • OBD II P0755

Fault Code Definition

  • Shift Solenoid B Malfunction
What does this mean?
The purpose of the automatic transmission is to match the engine's optimum power and torque characteristics to the driver's desired rate of acceleration and speed by auto-selecting different gear ratios or 'speeds' to power the wheels. Shift solenoid B enables the transmission to shift from 2nd gear to 3rd gear. It does this by re-directing the flow of the transmission fluid which changes the position of the shift valves in the valve body. 
When the code P0755 is set in the Powertrain Computer, it means that the Powertrain Computer or PCM is not seeing the specified rpm change that occurs during a shift from 2nd gear to 3rd gear. It's also not seeing the correct increase in road speed from the vehicle speed sensor. 

Symptoms

  • Check Engine Light will illuminate
  • Vehicle will not shift from 2nd gear to 3rd gear properly
  • Decrease in fuel economy
  • In unusual cases, there are no adverse conditions noticed by the driver
  • In some cases, there may be performance problems and possibly misfire-like symptoms

Common Problems That Trigger the P0755 Code

  • Defective Shift Solenoid
  • Defective Shift Solenoid wiring or connector
  • Defective Valve Body
  • Dirty transmission fluid that restricts the hydraulic passages

Common Misdiagnoses

  • Engine Misfire problem
  • Driveline problem

Polluting Gases Expelled

  • HCs (Hydrocarbons): Unburned droplets of raw fuel that smell, affect breathing, and contribute to smog
  • CO (Carbon Monoxide): Partially burned fuel that is an odorless and deadly poisonous gas
  • NOX (Oxides of Nitrogen): One of the two ingredients that, when exposed to sunlight, cause smog

P0755 Diagnostic Theory for Shops and Technicians

When diagnosing a P0755 code, it is important to record the freeze frame information and then to duplicate the code setting conditions with a test drive at speeds around 15-35 mph. Start out from a dead stop and gently accelerate. Watch the scan data to see if the PCM is commanding the solenoid to shift. If the PCM is giving the 2-3 shift command and the vehicle does not properly shift from 2nd to 3rd gear, then you will have verified a problem that could set the P0755 code. Next step is to start doing pinpoint tests i.e voltage drops and continuity tests of the shift solenoid. I generally back probe the wiring harness so I don't have to disassemble the transmission.  And, ALWAYS check the condition of the fluid. Is it dirty, brown and burnt or is it that clear cranberry color?

 


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