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Error Code P0775 is defined as insufficient fluid pressure within a solenoid working the automatic transmission, usually caused by leaks, low, or dirty transmission fluid.
This code is a generic trouble code, meaning it applies to all vehicles equipped with the OBD-II system, or vehicles made since 1996 up to present. Specifications on the definition, troubleshooting, and repairs of course, vary from one make and/or model to another.
When Error Code P0775 takes place that means the PCM (powertrain control module, also known as ECM or engine control module in other vehicle makes) has detected an abnormality in the solenoid circuit or electric pressure solenoid. The PCM controls the automatic transmission by using different degrees of hydraulic pressure, providing shift actuation and torque converter lockup. One or more electronic pressure control solenoids regulate the pressure, which are also controlled by the PCM.
Basically, the P0775 is a generic code for insufficient fluid pressure within the solenoid that operates the automatic transmission. When the code happens, the hydraulic solenoid in the transmission is not getting the proper amount of pressure from the hydraulic fluid. The solenoids are the ones responsible for controlling the torque converter and moving the transmission gear. Insufficient fluid pressure means the solenoids are not working properly.
Symptoms of this error code vary from non-detectable issues to symptoms that disable the shifting function or even torque converter clutch’s failure to engage or disengage. Of course, it also activates the Check Engine light on the dashboard. This code can also be accompanied with a “limp mode” set by the PCM. Other symptoms include:
- Transmission slippage
- Harsh transmission
- Increase in fuel consumption
There may also be error codes relating to torque converter clutch, shift solenoid, gear ratio, or transmission slippage problems to accompany this code.
The most common cause of this error code is faulty electronic pressure control solenoid and hydraulic blockage or leaks in the internal transmission fluid passages, not enough transmission fluid, dirty or contaminated transmission fluid, or mechanical internal transmission failures. Other possible causes include:
- Malfunctioning electronic control solenoid
- Electrical problem with transmission control module
- Defective or electrical problem with the PCM (rare)
How to Check
Before technicians make any significant diagnostic work, they first check the transmission fluid’s level and quality. In many cases, the problem stems from low or dirty transmission fluid. And with that, they address the problem by refilling or replacing the fluid with a new one.
After checking the fluid, technicians proceed on using OBD-II scanner to check the trouble code in real-time and see where it was first indicated. Then they reset the code, take the vehicle for a test drive and see if the code comes back. If the code comes back during the test drive, they can confirm if the original code was not a result of an electrical short or an intermittent problem.
Then they check the circuitry and wirings around the transmission control module, as well as the PCM to look for signs of damage or disconnections. They will test the circuitry using a voltmeter tool.
How to Fix
Repairs for this error code are pretty easy and straightforward, which of course, depends from the diagnosis. Repairs include:
- Repair or replacement of damaged wirings or corroded circuitry
- Replacement or addition of transmission fluid
- Repair or replacement of transmission
- Repair or replacement of high pressure pump
- Repair or replacement of electronic pressure control solenoid
Many times, people unnecessarily replace parts such as electronic pressure control solenoid, high pressure pump, and wiring harness in an attempt to fix this error code. Usually however, the problem is caused by insufficient or poor transmission fluid quality. Intermittent or small issues can also appear, thus, it is always important to conduct a proper diagnosis when Error Code P0775 appears.
This code can hinder the performance of the vehicle through the transmission. If the transmission is put in “limp mode” or there are other issues within the transmission that keeps the vehicle from running properly, fuel economy will definitely suffer.