P0797 – Pressure Control Solenoid “C” Stuck On

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

Definition source: SAE J2012/J2012DA (industry standard)

P0797 indicates the powertrain control system has detected that the transmission pressure control solenoid identified as “C” is stuck on (commanded or hydraulically acting as on when it should not be). This code describes a functional state issue, not a guaranteed part failure, and the exact detection logic can vary by vehicle, transmission design, and control strategy. In practice, the control module monitors solenoid command states and transmission response (such as pressure behavior and shift outcomes) to decide whether the solenoid appears stuck on. Always confirm the code’s setting conditions, related data parameters, and any required preliminary checks using the correct service information for the specific vehicle.

What Does P0797 Mean?

P0797 means the powertrain control system has determined that Pressure Control Solenoid “C” is stuck on. Based on the official definition, the fault is focused on the solenoid’s “stuck on” condition rather than a specific “circuit high/low/open” electrical designation. SAE J2012 defines how DTCs are structured and named; however, the meaning here is strictly that the controller believes the pressure control solenoid labeled “C” is remaining on when it should be off, or the transmission’s response indicates it is not turning off as commanded. Accurate diagnosis requires verifying commands versus results and checking for conditions that can make a solenoid behave as if it is continuously applied.

Quick Reference

• Subsystem: Automatic transmission hydraulic pressure control (Pressure Control Solenoid “C” control and resulting pressure/shift behavior).
• Common triggers: Solenoid commanded off but pressure/shift response indicates it remains applied; inconsistent line pressure regulation; controller detects abnormal response while toggling solenoid states.
• Likely root-cause buckets: Wiring/connector issues, solenoid/valve body sticking, power/ground concerns, hydraulic contamination/restriction, control module/driver or calibration issues (varies by vehicle).
• Severity: Often moderate to high; may cause harsh/erratic shifting, reduced drivability, and protective operation modes.
• First checks: Scan for related transmission codes, verify fluid level/condition, review freeze-frame data, inspect external harness/connectors, and compare commanded versus actual behavior in live data.
• Common mistakes: Replacing the solenoid immediately without verifying power/ground integrity, connector pin fit, fluid condition, or whether another fault is forcing abnormal pressure control.

Theory of Operation

Pressure control solenoids regulate hydraulic pressure within an automatic transmission by modulating fluid flow through valves in the valve body. The control module commands the solenoid on/off or with a duty-cycle strategy (varies by vehicle) to achieve target pressure for smooth shifts and clutch/band application. When operating correctly, changes in solenoid command produce predictable changes in transmission behavior, such as shift quality and pressure-related parameters reported through available sensors or inferred calculations.

P0797 sets when the controller determines Solenoid “C” behaves as if it is continuously on. This may be concluded by comparing the commanded state to observed pressure/shift response, monitoring adaptation limits, or detecting a lack of expected change when the solenoid is commanded off. Electrical faults, mechanical sticking, contamination, or hydraulic restrictions can all create an “always on” effect, so testing must separate command, electrical integrity, and hydraulic response.

Symptoms

• Harsh shifts: Upshifts or downshifts may feel abrupt due to improper pressure regulation.
• Erratic shifting: Unpredictable shift timing, flare, or bind may occur as commanded pressure does not match actual behavior.
• Limited operation: Transmission may enter a protective or reduced-function mode to prevent damage.
• Slip or bind: Clutch apply/release events may slip (under-apply) or bind (over-apply) depending on how pressure is affected.
• Delayed engagement: Delay when shifting into drive or reverse can occur if pressure control is not responding correctly.
• Warning indicator: A malfunction indicator or transmission warning may illuminate and store P0797 with related data.

Common Causes

• Connector or terminal issues at the pressure control solenoid “C” (loose fit, corrosion, backed-out pin, fluid intrusion)
• Harness damage in the solenoid control circuit (chafing, pinched wiring, contact with hot or moving components)
• Short-to-power or unintended feed on the solenoid control circuit causing the solenoid to remain energized
• Internal sticking of pressure control solenoid “C” (mechanical/hydraulic sticking) leading to an “on” condition
• Restricted or contaminated transmission fluid passages affecting pressure regulation behavior (varies by vehicle design)
• Valve body or hydraulic control assembly issues that keep pressure command/effect in an “on” state (varies by vehicle)
• Power/ground integrity problems affecting transmission/solenoid operation (poor ground, shared ground issues, excessive voltage drop)
• Control module driver or internal fault that keeps the solenoid commanded on (less common; verify all external causes first)

Diagnosis Steps

Tools helpful for diagnosing P0797 include a capable scan tool with live-data logging and bidirectional controls (if supported), a digital multimeter, and wiring diagrams/service information. For circuit integrity checks, back-probing tools and terminal test adapters help prevent connector damage. If access permits, basic hand tools for connector/harness inspection are useful. Some checks vary by vehicle, so confirm connector locations, pinouts, and test procedures in service information.

1. Confirm the code and capture data: Verify P0797 is active or stored. Record freeze-frame and any transmission-related companion DTCs. If multiple solenoid or pressure-related codes are present, diagnose them in the order directed by service information.
2. Check basic operating conditions: Verify transmission fluid level and obvious fluid condition concerns per service information (procedure varies by vehicle). Do not assume a fluid issue is the cause; use it as context for the rest of the testing.
3. Clear and perform a controlled retest: Clear DTCs and perform a short road test under similar conditions to the freeze-frame (where safe). If P0797 returns quickly, treat it as a hard fault; if it takes time, plan for longer logging and a wiggle test.
4. Visual inspection of wiring and connectors: Inspect the harness routing to the transmission/solenoid assembly for chafing, pinch points, and signs of heat damage. Inspect connectors for bent pins, corrosion, loose terminal tension, and any evidence of contamination. Repair obvious issues before deeper testing.
5. Wiggle test with live data: With the scan tool monitoring related data (such as solenoid command/status if available and other transmission parameters), gently manipulate the harness and connectors. Look for sudden changes or dropouts that correlate with movement, indicating an intermittent wiring/terminal fault.
6. Verify command vs. behavior (if bidirectional control is supported): Use the scan tool to command the pressure control solenoid “C” on/off (or different duty levels, if applicable) and observe whether the system response changes in a consistent way. If the solenoid appears “stuck on” regardless of command, prioritize electrical checks for unintended power/driver faults and mechanical sticking possibilities.
7. Circuit checks for an “always on” condition: Using wiring diagrams, identify the solenoid’s feed and control/driver circuit (varies by vehicle). Key on, engine off, check whether the solenoid control circuit shows evidence of being energized when it should not be. If the circuit indicates constant energization, isolate whether it is coming from a short-to-power in the harness or a control module driver issue by disconnecting the solenoid/connector and rechecking per service information.
8. Voltage-drop testing on power and ground: With the circuit loaded (where applicable and safe), perform voltage-drop tests across the solenoid feed and ground paths and across suspect connectors. Excessive drop indicates resistance in wiring, splices, grounds, or terminals that can skew control behavior and contribute to a stuck-on condition.
9. Check solenoid coil integrity (vehicle-specific procedure): With the circuit powered down as required, measure solenoid coil resistance and compare to service specifications. Results that are out of specification support a solenoid fault, but correct resistance does not rule out sticking or an intermittent internal issue.
10. Mechanical/hydraulic evaluation if electrical tests pass: If wiring, connectors, power/ground, and command signals test normal, consider that the solenoid or hydraulic control components may be sticking. Follow service information for access, inspection, and any functional checks of the solenoid, valve body, or related components (procedures vary by vehicle).
11. Module/driver evaluation last: If external circuits and the solenoid/hydraulic components check out, follow service information for control module output/driver diagnostics. Only consider module replacement/programming after confirming no shorts, no connector issues, and no component faults remain.

Professional tip: When diagnosing a “stuck on” solenoid fault, prioritize proving whether the solenoid is being commanded on or is being unintentionally energized. Logging live data during the exact conditions that set the code, combined with isolation testing (disconnecting the solenoid to see if the “on” condition persists), often prevents unnecessary solenoid or module replacement.

Possible Fixes & Repair Costs

Repair cost for P0797 varies widely because it depends on confirming why pressure control solenoid “C” is being commanded or behaving as “stuck on,” plus access to the transmission components, parts replacement needs, and labor time. Diagnose first to avoid unnecessary repairs.

• Repair wiring/connector issues affecting the pressure control solenoid “C” circuit (clean terminals, correct pin fit, repair damaged insulation, restore secure grounds and power feeds as applicable).
• Service the solenoid connection point (internal or external harness/connector service varies by vehicle) after verifying the fault follows the circuit and not a control command.
• Replace pressure control solenoid “C” only after testing confirms it is mechanically sticking or not responding correctly under commanded control.
• Address hydraulic/mechanical contributors that can make a solenoid appear “stuck on” (for example, restricted fluid flow or contamination) where service information supports inspection/cleaning procedures.
• Repair valve body or related hydraulic control components if verified that the solenoid is being commanded normally but pressure regulation is not responding as expected.
• Update or reprogram the control module if service information specifies a calibration fix and testing indicates command/feedback behavior consistent with a software issue.
• Replace the control module only after power/ground integrity, circuit checks, and component tests rule out wiring, solenoid, and hydraulic causes.

Can I Still Drive With P0797?

You may be able to drive short distances, but P0797 can be associated with harsh shifting, abnormal pressure control, and reduced drivability that could worsen quickly. If you notice severe slipping, sudden loss of acceleration, a failsafe/limited-gear condition, or any warning that affects braking/steering or creates unsafe operation, do not drive and arrange service. Even when the vehicle feels “mostly normal,” minimize load, avoid towing, and verify the condition with proper diagnosis as soon as possible.

What Happens If You Ignore P0797?

Ignoring P0797 can lead to progressively worse shift quality and increased stress on transmission components if pressure control remains abnormal. Continued operation may accelerate clutch/band wear, increase heat, and raise the chance of drivability complaints or a failsafe strategy that limits available gears. The longer it persists without identifying the cause, the more difficult it can be to distinguish an initial electrical/control issue from secondary mechanical wear.

Related Pressure Solenoid Codes

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

• P0747 – Pressure Control Solenoid “A” Stuck On
• P0777 – Pressure Control Solenoid “B” Stuck On
• P0762 – Shift Solenoid “C” Stuck On
• P0757 – Shift Solenoid “B” Stuck On
• P0752 – Shift Solenoid “A” Stuck On
• P0749 – Pressure Control Solenoid “A” Intermittent

Key Takeaways

• P0797 indicates “Pressure Control Solenoid ‘C’ Stuck On” and should be treated as a control/response problem until testing confirms a specific failure.
• Diagnosis should start with circuit integrity (connectors, harness routing, power/ground quality) before replacing parts.
• Command vs. response matters: confirm whether the module is commanding the solenoid on, or whether the solenoid/hydraulics are behaving as if it is on.
• Hydraulic issues can mimic an “on” condition, so combine electrical tests with scan-tool data and appropriate pressure/response checks where supported.
• Prompt repairs can prevent secondary damage caused by prolonged abnormal pressure regulation.

Vehicles Commonly Affected by P0797

• Vehicles with electronically controlled automatic transmissions that use multiple pressure control solenoids for line pressure and shift scheduling.
• Vehicles with integrated transmission control where the engine controller or a dedicated controller manages solenoid commands.
• Vehicles operating in high-heat or high-load duty cycles (frequent stop-and-go driving, heavy loads, steep grades) that stress fluid and hydraulic control.
• Higher-mileage vehicles where harness flexing, connector wear, and internal transmission deposits become more likely.
• Vehicles exposed to corrosion environments that can affect external connectors and grounds associated with transmission controls.
• Vehicles with prior transmission service history where fluid contamination, incorrect assembly, or connector disturbance could contribute to a recurrence.
• Vehicles with known charging or battery issues that can impact module control stability and solenoid actuation consistency.
• Vehicles that frequently enter failsafe mode due to intermittent transmission control or sensor-related faults that can coincide with pressure control concerns.

FAQ

Does P0797 automatically mean pressure control solenoid “C” is bad?

No. P0797 means the control system detected pressure control solenoid “C” as “stuck on,” but that can be caused by wiring/connector problems, a control command issue, or hydraulic/mechanical conditions that make the transmission behave as if the solenoid is continuously applied. Testing is required to confirm the root cause.

Can low or contaminated transmission fluid cause P0797?

Depending on vehicle design, fluid level/condition problems can contribute to abnormal hydraulic behavior that may mimic or worsen pressure control issues. However, P0797 is not a fluid-quality confirmation by itself. Check fluid condition and level using the correct procedure for the vehicle, then continue with electrical and command/response diagnosis.

What should I look at first before replacing parts?

Start with basics: scan for related transmission and power supply codes, verify battery/charging stability, inspect the transmission connector(s) for corrosion or pin fit issues, and check harness routing for chafing. If supported by your scan tool, compare commanded solenoid operation to actual shift/pressure behavior and log data during the event.

Will clearing the code fix P0797?

Clearing the code only resets stored fault information; it does not correct the underlying condition. If the issue remains, the monitor is likely to fail again and the code will return, sometimes along with drivability symptoms or a failsafe strategy.

Is P0797 an electrical problem or a mechanical problem?

P0797 is best approached as a control/response problem: it may be electrical (circuit/connector/power/ground), electro-mechanical (solenoid sticking), or hydraulic/mechanical (valve body or fluid flow issues) depending on the design. A structured test plan that separates command from response is the fastest way to pinpoint which category applies.

For a reliable repair, confirm whether the solenoid is being commanded on continuously or whether it behaves “on” despite normal commands, then fix only the verified cause.