P0779 OBD-II Trouble Code: Pressure Control Solenoid B Intermittent
P0779 Code Definition
The P0779 code is a generic powertrain code related to the transmission, including sensor failures and pressure faults. In this case, the engine control module (ECM) has detected a fault with Pressure Control Solenoid B, receiving intermittent voltage signals.
Codes related to the P0779 include:
- P0775: Pressure Control Solenoid "B"
- P0776: Pressure Control Solenoid "B" Performance or Stuck off
- P0777: Pressure Control Solenoid "B" Stuck On
- P0778: Pressure Control Solenoid "B" Electrical
What the P0779 Code Means
The automatic transmission is controlled by the ECM with varying degrees of hydraulic pressure, which provides shift actuation and torque converter lock up. Utilizing electronic pressure control solenoids, which are controlled by the ECM, the hydraulic pressure is regulated.
The parameters for which a P0779 code can be set varies by each automaker, so check your service manual for specifics for your vehicle’s make and model. However, typically the ECM utilizes calculations from several sensors, including the pressure control sensor, to determine how much pump pressure is needed for operation. When the transmission fluid pressure doesn’t match the amount the ECM detects, a P0779 code can be stored.
What Causes the P0779 Code?
Several problems may cause a P0779 code including:
- Low transmission fluid
- Dirty or contaminated transmission fluid
- Damaged or defective electronic pressure control solenoid
- Hydraulic blockage inside transmission fluid passages
- Transmission failure
- Damaged or defective transmission control module
- Damaged or defective ECM (rare)
What are the Symptoms of the P0779 Code?
Symptoms of a P0779 code may include:
- Check Engine or Warning Light may illuminate
- There may be no discernable symptoms for a P0779 code
- The torque converter clutch may not engage
- The torque converter clutch may not disengage
- The vehicle may shift roughly
- The vehicle may not shift in or out of gear (including park)
- Decreased fuel economy
- The transmission may overheat
- You may experience transmission slippage
- The transmission may enter “limp” mode
How Does a Mechanic Diagnose the P0779 Code?
A mechanic may use several methods to diagnose a P0779 trouble code, including:
- Utilize an OBD-II scanner to check for a stored P0779 trouble code
- Check transmission fluid level
- Check transmission fluid quality
- If transmission fluid is dirty, check transmission pan for contamination and debris
- Check related wiring and circuitry for damage or corrosion
- Check for any transmission fluid leaks
- Use a manual pressure gauge to check transmission pump pressure
- Check for clogged hydraulic passages
- Check for reference voltage and ground signals at electronic pressure control solenoid B
- Use a digital volt/ohmmeter to check all circuits for continuity and resistance
Common Mistakes when Diagnosing the P0779 Code
At times, a high pressure pump may be replaced in oversight of a faulty electronic pressure control solenoid or damaged or malfunctioning wiring. It is recommended to test all system circuitry and repair any damage within before replacing the high pressure pump.
How Serious is the P0779 Code?
Because a vehicle’s safe driving operation most likely will be impacted due to faults that store a P0779 code, this code is considered a potentially serious code. When this code appears, it is recommended to immediately take your vehicle to your local service center or mechanic for repair and diagnosis.
What Repairs can Fix the P0779 Code?
Several repairs can fix a P0779 trouble code and include:
- Fill transmission fluid to manufacturer recommended levels
- Perform a transmission fluid service
- Rebuild transmission, flush fluids, replace torque converter if clutch material or debris is located in transmission pan
- Repair any damaged or shorted, open, or loose wiring or connectors
- Repair any transmission fluid leaks
- Clear any clogged hydraulic passages
- Repair or replace damaged or defective high pressure pump
- Repair or replace damaged or defective pressure control solenoid B
- Repair or replace damaged or defective torque converter
- Repair or replace damaged or defective ECM (rare)
- Clear all codes, test-drive the vehicle, and rescan to see if any codes reappear
Need Help with a P0779 Code?
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