Error Code P0751: What It Means & What To Do?

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OBD II fault code P0751 is a generic code that is defined as “Shift solenoid (SS) “A” -performance or stuck off” and is set when PCM detects an abnormality in shift solenoid A. Automatic transmissions use solenoids to move fluid through interior channels and create the pressure needed to change gears. If the PCM detects a difference in the actual gear ratio as compared to the gear ratio predicted by the engine speed, throttle position and other factors, it will set the P0751 code.

Diagnostic trouble code P0751 is technically described as Shift Solenoid A Performance or Stuck Off. This is a generic transmission diagnostic trouble code (DTC) and typically applies to OBD-II vehicles equipped with an automatic transmission. The computer controlled automatic transmission uses shift solenoids to manage the transfer of fluid between hydraulic circuits and actuate a change in transmission gear ratio. Varying gear ratios are needed to increase and decrease vehicle speed, maximize engine performance, and optimize fuel efficiency. If the desired gear ratio fails to coincide with the actual gear ratio detected, a code will be stored and a malfunction indicator lamp may be illuminated.

What causes this problem with the Shift Solenoid A Performance or Stuck Off?

• Filthy transmission fluid
• Reduced level of transmission fluid
• Defected shift solenoid A valve
• Hydraulic blockages inside the internal transmission fluid passages
• Flawed or corroded wiring and connector
• Clogged transmission filter
• Faulty PCM

1. Shift Solenoid - A shift solenoid is a component of a vehicle's transmission system regulating the transmission fluid levels in a car. This computerized component of a car automatically controls the transmission fluid levels, allowing the right amount of fluid to flow in and out of the transmission. The shift solenoid is located on the transmission's internal valve body or on the outside of the transmission case. If you discover it faulty replace it immediately.
2. Shift Valves - shift valve directs line pressure to the circuit selected by the gear selector. It's connected mechanically to the gear selector by the shift cable. Replace the fallacious shift valves in no time else can create serious problems.
3. Transmission filter - The transmission filter is there to keep contaminating particles out of the transmission fluid. However, if the filter fails to keep particles out, the transmission fluid will quickly reach a point where it is too dirty to do its job efficiently.
4. Transmission Valve Body - The valve body is the control center of the automatic transmission. It contains a maze of channels and passages that direct hydraulic fluid to the numerous valves which then activate the appropriate clutch pack or band servo to smoothly shift to the appropriate gear for each driving situation. It should be inspecting thoroughly and replace or repair as required.
5. Powertrain Control Module - A powertrain control module, abbreviated PCM, is an automotive component, a control unit, used on motor vehicles. It is generally a combined control unit, consisting of the engine control unit (ECU) and the transmission control unit (TCU). Faulty PCM should be repaired or replaced immediately.

Some common symptoms for this trouble code P0751 are below mentioned. If you discover any one of them, kindly take your vehicle to the reputed repair facility.

• Transmission may overheat
• Transmission may enter into Limp mode
• Other transmission error codes may store as well
• Transmission slippage
• Decreased fuel efficiency
• Illuminated check engine light

Trouble code P0751 should be diagnosed and addressed immediately as this can affect the drivability of your car and if avoided can lead to serious transmission damage. To fix this code following repairs and replacements may help:

• Replace the dirty or contaminated transmission fluid.
• Check the level of transmission fluid and top up if required.
• Look for the faulty wiring and loose or broken connector, repair or replace if required.
• Always replace the faulty shift solenoid A.
• Valve body should also be replaced if found faulty.

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To avoid any mistakes while diagnosing this code, it is always recommended to have your vehicle diagnosed with the help of qualified technician. Steps to diagnose this code are as follows:

• Record all fault codes present, as well as all available freeze frame data. This information can be of use should an intermittent fault be diagnosed later on.
• If the application is fitted with a dipstick, check the fluid level as per the instructions in the manual, and adjust the level as required. Also check the condition of the fluid; if it is dark in color, has a burnt smell, or has a thick, tarry consistency, the fluid is degraded and it must be replaced.
• If the fluid is up to the proper mark and in good condition, locate the transmission wiring harness, and inspect it for damage or corrosion. Also perform a thorough visual inspection of all related wiring- look for damaged, burnt, shorted, disconnected, or corroded wiring. Repair or replace wiring or the connector as required.
• If the connector is in good condition, refer to the manual to determine the function and color coding of each wire in the connector. Identify the wires that relate to shift solenoid “A” in the transmission side of the connector, and perform resistance and continuity checks on these wires as per the instructions in the manual.

Common Mistakes When Diagnosing the P0751 Code

Most commonly, mechanics will replace shift solenoid A without conducting a full diagnosis. While a failed solenoid is often the culprit, there are other factors that must be ruled out. Often, low transmission fluid is the problem.