P0779 – Pressure Control Solenoid “B” Intermittent

System: Powertrain | Standard: ISO/SAE Controlled | Fault type: General | Location: Designator B

Definition source: SAE J2012/J2012DA (industry standard)

P0779 is a powertrain diagnostic trouble code that indicates the control module has detected an intermittent condition involving Pressure Control Solenoid “B.” “Intermittent” means the fault is not continuously present; it may appear and disappear depending on temperature, vibration, harness movement, internal solenoid behavior, or operating conditions. Because monitoring strategy, solenoid naming, and the transmission’s hydraulic layout vary by vehicle, the exact enable criteria and when the code sets can differ between platforms. Use the factory service information for connector views, terminal IDs, test procedures, and specifications. Treat P0779 as an electrical/control integrity issue first, and confirm the root cause with testing before replacing parts.

What Does P0779 Mean?

P0779 – Pressure Control Solenoid “B” Intermittent means the powertrain control system has detected that the pressure control solenoid identified as “B” is not behaving consistently. Under normal operation, the module commands this solenoid to help regulate transmission hydraulic pressure; it also evaluates whether the commanded action produces the expected response. If the solenoid control or feedback behavior is unstable—such as sporadic operation, inconsistent electrical continuity, or an on-and-off fault that does not remain steady—the module may set P0779. SAE J2012 defines the DTC structure and naming conventions, while the specific monitoring details and solenoid “B” identification depend on the vehicle’s service documentation.

Quick Reference

  • Subsystem: Transmission hydraulic pressure control circuit for Pressure Control Solenoid “B” (control and related wiring/connectors).
  • Common triggers: Intermittent electrical connection, harness movement/vibration sensitivity, unstable solenoid coil operation, or inconsistent pressure-control response during certain shifts.
  • Likely root-cause buckets: Wiring/connector faults, solenoid (electro-hydraulic actuator) issues, power/ground integrity problems, valve body/internal harness concerns (varies by vehicle), or module/driver faults.
  • Severity: Often moderate; may cause harsh/erratic shifting or reduced performance, and can become severe if pressure control is lost or the condition worsens.
  • First checks: Scan for companion transmission codes, record freeze-frame, inspect connectors/pins and harness routing, verify power/ground integrity, and perform a wiggle test while monitoring live data.
  • Common mistakes: Replacing the solenoid immediately without verifying intermittent wiring/terminal fit issues, ignoring power/ground voltage-drop testing, or diagnosing without reproducing the fault conditions.

Theory of Operation

Pressure control solenoids are used to regulate hydraulic pressure inside the transmission so that clutches and bands apply smoothly and consistently. The control module commands the solenoid “B” electrically (design varies by vehicle) to influence pressure, then evaluates the resulting behavior using available feedback. Depending on the design, feedback may be inferred from transmission input/output speed changes, shift timing, commanded versus achieved pressure behavior, or other monitored signals.

For an intermittent fault, the module sees the solenoid’s control behavior or the system response become unstable rather than consistently wrong. This can occur when electrical continuity changes moment-to-moment (loose terminals, corrosion, internal harness issues), when the solenoid coil or internal components act inconsistently as they heat or vibrate, or when the driver circuit intermittently fails to control the solenoid as commanded.

Symptoms

  • Harsh shifting: Firmer-than-normal upshifts or downshifts that come and go.
  • Erratic shift timing: Delayed shifts, unexpected shift feel changes, or intermittent shift flare depending on conditions.
  • Limp strategy: Reduced shifting functionality or fixed-gear operation that may be intermittent.
  • Warning indicator: Malfunction indicator lamp or transmission warning message, sometimes with intermittent return after clearing.
  • Performance change: Reduced acceleration responsiveness due to altered shift scheduling or pressure management.
  • Converter behavior: Intermittent lockup feel changes or shudder-like sensations if pressure control affects related functions (varies by vehicle).

Common Causes

  • Intermittent open or high resistance in the Pressure Control Solenoid “B” control circuit wiring (including inside the harness)
  • Poor connector pin fit, corrosion, moisture intrusion, or terminal damage at the solenoid, transmission pass-through, or control module connector
  • Intermittent power feed or ground issue affecting the solenoid circuit (shared splice, fuse feed, ground point, or internal harness connection)
  • Pressure Control Solenoid “B” internal fault that appears only under certain temperature, vibration, or duty-cycle conditions
  • Transmission internal harness or pass-through connector intermittent connection (varies by vehicle design)
  • Control module driver/control issue for the solenoid (less common; verify all external circuit integrity first)
  • Fluid contamination or debris affecting solenoid movement, leading to inconsistent response that the module interprets as intermittent operation (verify with testing; not confirmed by the DTC alone)
  • Aftermarket wiring repairs or prior service work leading to intermittent contact (pinched wiring, poor crimp, incorrect terminal)

Diagnosis Steps

Tools typically needed include a scan tool capable of viewing live data and commanding transmission solenoids (where supported), a digital multimeter, and back-probing tools. A wiring diagram and connector pinout from service information are essential because circuit routing varies by vehicle. If accessible, basic hand tools for connector inspection and a means to safely raise/support the vehicle may be required for harness checks.

  1. Confirm the DTC and capture scan tool data. Record freeze-frame data, current/previous status, and any companion transmission or power/ground DTCs. Clear codes and note whether P0779 resets immediately or only after a drive cycle.
  2. Perform a quick visual inspection. Check for obvious harness damage, fluid contamination at connectors, loose retainers, or signs of overheating near the transmission case, exhaust routing, and any harness brackets that can chafe wiring.
  3. Verify the concern is intermittent. With the vehicle safely secured, run the engine (as appropriate) and monitor relevant live data parameters for solenoid command/operation (names vary by vehicle). Look for dropouts, sudden changes, or inconsistent readings that coincide with vibration, gear changes, or temperature changes.
  4. Check for related power/ground integrity issues first. Using the wiring diagram, identify the solenoid’s shared power feed and ground strategy (direct ground, module-controlled ground, or module-controlled power varies by vehicle). Inspect fuses and related circuits, and address any powertrain voltage supply issues before focusing on the solenoid itself.
  5. Connector inspection and terminal checks. Disconnect the solenoid-related connectors (following service procedures). Inspect for bent pins, pushed-out terminals, corrosion, fluid intrusion, or poor terminal tension. Repair terminal issues as needed; do not assume cleaning alone resolves a loose pin fit.
  6. Wiggle test while monitoring. Reconnect as needed and, with the scan tool monitoring the solenoid-related data and/or DTC status, gently manipulate the harness and connectors from the transmission to the control module. If the fault status changes or data drops out, isolate the exact section by moving along the harness in smaller increments.
  7. Continuity and resistance checks (key off). With connectors unplugged and using the correct pinout, check the solenoid control circuit for opens and intermittent continuity issues end-to-end. Flex the harness during testing to reveal breakpoints. Also check for unintended continuity to adjacent circuits where the harness may be rubbed through.
  8. Voltage-drop testing under load (key on/commanded where supported). When the scan tool can command the solenoid, measure voltage drop across the power feed and ground/control side while the circuit is active. Excessive drop indicates high resistance in wiring, terminals, splices, or grounds. Consult service information for the proper method and expected results for that platform.
  9. Actuator functional test (if supported). Use bi-directional controls to command Pressure Control Solenoid “B” through its operating range and observe for consistent response. If the vehicle provides feedback parameters, compare commanded changes to observed behavior for signs of intermittent operation.
  10. Component and internal harness isolation (varies by vehicle). If external wiring tests good, isolate whether the intermittent fault follows the solenoid, the internal harness/pass-through, or remains with the vehicle-side harness/module. This may involve testing at the transmission pass-through connector and comparing results on both sides to pinpoint where the intermittency originates.
  11. Module-side verification (last). Only after wiring, terminals, power/ground integrity, and solenoid/harness checks are proven good should you consider a control module driver/control issue. Verify connector integrity at the module and repeat load/voltage-drop tests from the module connector to confirm the module is seeing a stable circuit.

Professional tip: Intermittent solenoid-related faults are often caused by terminal tension loss or a high-resistance splice that only fails with heat or vibration. If the code is difficult to reproduce, log live data during an extended drive cycle and repeat your wiggle test immediately after the symptom occurs, when the harness and connectors are at operating temperature.

Need wiring diagrams and factory-style repair steps?

Powertrain faults often require exact wiring diagrams, connector pinouts, and guided test steps. A repair manual can help you confirm the cause before replacing parts.

Factory repair manual access for P0779

Check repair manual access

Possible Fixes & Repair Costs

Repair costs for P0779 vary widely because the correct fix depends on what is causing the Pressure Control Solenoid “B” signal to be intermittent. Diagnosis time, component access, wiring repair complexity, fluid service needs, and parts availability all influence the final cost.

  • Repair wiring/connector issues: Clean, reseat, or replace damaged terminals; correct poor pin fit; repair chafed wiring; secure harness routing to prevent vibration-related opens.
  • Restore power/ground integrity: Correct poor grounds, corrosion, or high-resistance connections that can intermittently drop solenoid control or supply circuits.
  • Replace Pressure Control Solenoid “B”: Replace only after confirming the solenoid is intermittently failing electrically or mechanically per service information and test results.
  • Service transmission fluid and related items: If inspection shows incorrect fluid level/condition or contamination contributing to unstable pressure control, perform the specified service (varies by vehicle).
  • Repair internal transmission harness or pass-through connector: Address intermittent internal connection faults where the solenoid wiring routes through the case (design varies by vehicle).
  • Control module update or replacement: Consider only after verifying wiring, power/ground, and solenoid function; follow service information for any required programming or relearn steps.

Can I Still Drive With P0779?

You may be able to drive short distances if the vehicle feels normal, but P0779 can lead to unpredictable shifting or reduced transmission performance because the solenoid signal is intermittent. If you notice harsh shifts, slipping, delayed engagement, reduced power behavior, or any warning indicators that affect braking/steering control systems, limit driving and arrange diagnosis promptly. If the vehicle struggles to move safely, enters a fail-safe mode with very limited gear operation, or the condition worsens during driving, do not continue driving.

What Happens If You Ignore P0779?

Ignoring P0779 can allow an intermittent control problem to become more frequent, increasing the chance of harsh or erratic shifting, reduced drivability, and extended operation in a protective strategy. Continued unstable pressure control may contribute to elevated heat and wear over time, potentially turning an intermittent electrical or connection issue into broader transmission performance complaints that are harder to isolate.

Compare nearby pressure solenoid trouble codes with similar definitions, fault patterns, and diagnostic paths.

  • P0749 – Pressure Control Solenoid “A” Intermittent
  • P0799 – Pressure Control Solenoid “C” Intermittent
  • P0764 – Shift Solenoid “C” Intermittent
  • P0759 – Shift Solenoid “B” Intermittent
  • P0754 – Shift Solenoid “A” Intermittent
  • P0748 – Pressure Control Solenoid “A” Electrical

Key Takeaways

  • P0779 means intermittent behavior: The fault is defined as Pressure Control Solenoid “B” Intermittent, pointing to an unstable signal or operation rather than a constant failure.
  • Verify before replacing parts: Intermittent wiring/connector faults and power/ground integrity issues are common and should be proven with testing.
  • Logging helps catch it: Live-data logging and repeated test drives can be necessary to capture the condition when it occurs.
  • Fix what testing confirms: The correct repair can range from a connector repair to solenoid replacement, depending on results.
  • Don’t delay if symptoms worsen: Drivability changes or fail-safe operation are reasons to prioritize diagnosis.

Vehicles Commonly Affected by P0779

  • Vehicles with electronically controlled automatic transmissions: Systems that use pressure control solenoids for hydraulic pressure regulation.
  • Vehicles used in frequent stop-and-go driving: Operating patterns that can increase heat and cycling of solenoid control.
  • Vehicles exposed to moisture/corrosion environments: Conditions that can promote intermittent connector or ground issues.
  • Higher-mileage vehicles: Harness fatigue, terminal tension loss, and internal connector wear become more likely over time.
  • Vehicles with recent transmission or engine-bay service: Disturbed connectors, pin fit issues, or harness misrouting can create intermittent faults.
  • Vehicles with underbody harness exposure: Debris impact, abrasion, or fluid contamination can affect wiring integrity.
  • Vehicles that tow or carry heavy loads: Increased thermal stress can worsen marginal electrical connections or solenoid performance.
  • Vehicles with a history of low/incorrect fluid condition: Fluid-related issues can contribute to unstable hydraulic control and mask electrical intermittents.

FAQ

Does P0779 mean the pressure control solenoid “B” is bad?

No. P0779 indicates the module detected intermittent behavior related to Pressure Control Solenoid “B,” which can be caused by wiring/connector problems, unstable power/ground, an intermittent solenoid, or less commonly a control module issue. Testing is needed to confirm the cause.

What is the most common cause of an intermittent solenoid-related code like P0779?

Intermittent faults are often caused by wiring and connector issues such as poor pin fit, corrosion, rubbed-through insulation, loose connectors, or harness movement. A wiggle test, careful connector inspection, and voltage-drop testing are commonly used to prove this.

Can low or dirty transmission fluid set P0779?

It can contribute, depending on vehicle design and monitoring strategy, because unstable hydraulic pressure control may make the solenoid’s commanded vs. resulting behavior appear inconsistent. However, P0779 is not proof of a fluid problem; check fluid level/condition only as part of a complete diagnosis using service information.

Why does the code come and go?

Because the fault is intermittent, it may only occur under certain conditions such as vibration, temperature changes, harness movement, or specific operating states. The module may not detect the fault every drive cycle, so confirming the issue often requires live-data logging and repeatable test conditions.

Should I replace the solenoid immediately to clear P0779?

No. Replacing parts without confirming the cause is a common mistake with intermittent DTCs. Start with connector and harness checks, verify power/ground integrity, and confirm solenoid operation per service information. Replace the solenoid only when the evidence supports it.

If P0779 returns after repairs, recheck connector terminal tension, harness routing, and ground quality, and repeat live-data logging to confirm the intermittent condition is fully resolved.