Comprehensive Diagnostic Guide for OBD-II Code P0968

What This Code Means

• What the code means electrical circuit for Pressure Control Solenoid C. In other words, the code signals an electrical fault in the solenoid C circuit rather than a purely mechanical hydraulic fault. Some other definitions in the broader OBD-II landscape refer to circuit range/performance, but the provided Open Source entry clearly indicates an open circuit for solenoid C (P0968).
• Where this fits in: P0968 is a Powertrain Code (transmission-related) within the OBD-II framework. Modern OBD-II systems monitor transmission hydraulics via solenoids, and the solenoids are controlled by the Transmission Control Module (TCM) or Powertrain Control Module (PCM). When the solenoid C circuit is open, the TCM/PCM may not be able to command the proper hydraulic pressure, leading to shifting issues or related symptoms.

Symptoms (real-world symptom descriptions informed by common user reports)

• Transmission shifting problems:
  • Harsh, abrupt, or delayed upshifts/downshifts.
  • Slipping between gears or inability to hold a gear at expected speeds.
  • Occasional failure to move or "limp mode" behavior in severe cases.
• MIL illumination:
  • Check Engine or transmission-related warning light may come on, depending on vehicle and its Mil requirements.
• Driveability and performance:
  • Reduced performance or hesitation during acceleration.
  • Possible sensation of trans failing to engage properly or unusual transmission behavior during a road test.
    Note: Some symptoms may overlap with other transmission or electrical faults. A thorough diagnostic is required to confirm P0968 as the root cause.

Probable Causes

Because do not include NHTSA complaint statistics for P0968, the following probabilities are based on typical field experience and common failure modes observed by technicians, clearly labeled as such.

• Wiring harness/connectors to solenoid C (open circuit due to wiring or connection problems): 35-45%
  • Symptoms often tied to corrosion, damaged insulation, pin push-out, moisture intrusion, or loose/poorly seated connectors at the solenoid or the controlling module.
• Solenoid C coil or solenoid valve failure (internal short/open, coil degradation, mechanical sticking): 25-35%
  • An electrical fault inside the solenoid itself can create an open circuit condition or improper valve operation, leading to incorrect pressure control.
• Transmission control module (TCM/PCM) electrical fault or degraded driver output (faulty grounding, power supply issues, software/firmware anomaly): 10-15%
  • Faulty driver or intermittent control capability can mimic an open-circuit condition or fail to energize the solenoid properly.
• Wiring/grounding issues elsewhere in the circuit (including ground paths and power supply lines to the TCM/solenoid circuit): 5-10%
  • Intermittent grounding or voltage drop can produce symptoms similar to an open circuit.
• Software or calibration issue (TCM/PCM programming or software update needed): 5-10%
  • In some cases, a reflash or software update may resolve miscommunication to the solenoid or timing of the command signals.
• Mechanical hydraulic concerns (low fluid level, contamination, or valve body issues) that influence hydraulic performance rather than directly causing an electrical open circuit: 0-5%
  • These do not cause an electrical open circuit, but they can produce related symptoms; they should be checked to avoid masking the true electrical fault. (Caveat: hydraulic issues can cause transmission symptoms, but P0968 specifically indicates an electrical/open-circuit condition of solenoid C)

Diagnostic Approach

1) Confirm the DTC and collect data

• Use an appropriate scan tool to confirm P0968 is present and review freeze-frame data.
• Check for any related DTCs (e.g., other pressure solenoid circuits, solenoid driver faults, or transmission-related codes) that can help triangulate the issue.
• Note vehicle make/model, engine/transmission type, and whether the code appears under generalized "P" codes or is accompanied by manufacturer-specific codes.

2) Visual inspection and basic electrical checks

• Inspect the solenoid C harness and connectors for signs of damage, corrosion, moisture, or improper seating. Pay attention to damaged insulation, pin deformation, or bent/loose pins.
• Inspect the connector at the solenoid C and the corresponding TCM/PCM connector for corrosion or contamination.
• Check for obvious damage along the harness routing (chafing, abrasion, or heat sources).
• Safety: ensure ignition is off, battery disconnected if you'll be unplugging connectors or performing resistance checks that could short or arc; use appropriate PPE and catch any leaked transmission fluid.

3) Electrical circuit testing (solenoid C circuit)

• With the ignition and engine off, perform continuity checks on the solenoid C circuit wires from the harness connector to the solenoid connector and to the TCM/PCM input/output points as specified by the vehicle's wiring diagram.
• Check for short to ground or short to power at the solenoid circuit.
• With the ignition on (engine may be running for certain tests per vehicle's service procedure), verify that the solenoid receives the appropriate voltage when commanded by the TCM/PCM. If the solenoid is expected to be energized under certain conditions, verify it is getting voltage during those conditions.
• If continuity is good but voltage is not present during commanded operation, the issue may be with the control circuit (TCM/PCM driver or wiring). If voltage is present but the circuit still shows open behavior, the solenoid or its solder joints may be defective. (General electrical testing approach; not vehicle-specific)

4) Solenoid coil resistance testing (coil health)

• If access allows, measure the coil resistance of solenoid C against OEM specifications. A coil that is open or out of tolerance suggests a faulty solenoid.
• Note: Specific resistance values vary by vehicle. Do not use a one-size-fits-all number; compare to the manufacturer's spec in the service documentation. (Solenoid coil testing is a standard diagnostic step; no vehicle-specific numbers are provided )

5) Live data and functional tests

• Using a scan tool with live data, observe the commanded state of solenoid C and, if supported, the actual solenoid activity/current draw.
• Look for delayed or absent solenoid response when the TCM/PCM commands it, or erratic/low current draw indicating an internal coil problem or wiring issue.
• If applicable, perform a functional test (actuate the solenoid in a controlled manner as per service procedures) to see how the system responds in real time.

6) Check for related power/ground integrity

• Inspect the grounding path for the transmission controller (TCM/PCM) as well as the solenoid circuit ground. A poor ground can mimic an open circuit condition.
• Verify the supply voltage to the solenoid circuit is within expected range and that there are no excessive voltage drops along the run to the solenoid.
• Ensure the TCM/PCM power supply and ignition-switched power are stable during operation. (General electrical diagnostics; not vehicle-specific)

7) Cross-check with data from the TCM/PCM and vehicle software

• If all wiring and the solenoid test as good, consider software-related faults. Some vehicles respond to TCM software updates or recalibration; verify whether any OEM software updates exist for the vehicle. (Software considerations; supported by general OBD-II and powertrain code discussions)

8) Mechanical/ hydraulic considerations (as context)

• While P0968 points to an electrical open circuit for solenoid C, hydraulic issues can produce similar shifting symptoms. Check transmission fluid level and condition, and inspect for leaks or contamination. If hydraulic issues are suspected, they should be addressed without assuming the electrical fault is resolved solely by fluid changes. (General transmission knowledge; not a direct P0968 cause)

9) Road test and confirmation

• After restoring or replacing the faulty circuit path (wiring/connector/solenoid/ground) and clearing the code, perform a road test to confirm that the transmission shifts normally and that the DTC does not return.
• Re-scan to verify the code does not reappear and that freeze-frame data reflect normal operation after repair.

What to do if you identify the fault

• Wiring/connector problems or intermittent open circuit
  • Repair or replace damaged wiring, reseat connectors, apply dielectric grease if appropriate, and ensure robust shielding from heat and moisture.
• Faulty solenoid C coil or valve
  • Replace the solenoid assembly or the valve body as per OEM service procedures; in some transmissions you may replace the entire valve body module.
• Faulty TCM/PCM driver or grounding issue
  • Inspect and repair grounds, inspect the TCM/PCM power supply, or perform a software reflash/update if approved by the OEM.
• Software/ calibration issue
  • Apply OEM-released software update or reflash and re-test. (Software-related fixes are a recognized path when wiring and hardware checks pass but codes persist)

Safety and quality considerations

• Handling transmission fluid: use proper PPE, catch and contain leaks, and dispose of fluids properly. Transmission fluid is hot and can cause burns.
• If you suspect a high-pressure system issue or valve body service, ensure the vehicle is properly supported and depressurized as per service procedures to avoid injury.
• When in doubt, verify that the code is not a result of a cascading failure (e.g., an upstream electrical problem causing a misread of the solenoid circuit).

Helpful references to sources

• OBD-II general code and diagnostic trouble codes overview: Wikipedia - OBD-II; Diagnostic Trouble Codes
  • Provides general context for how DTCs are used and monitored in modern vehicles.
• OBD-II Powertrain Codes: Wikipedia - OBD-II; Powertrain Codes
  • Confirms that P-codes belong to the powertrain subsystem and relate to drivetrain control systems, including transmission components.
• Emissions Testing (contextual): Wikipedia - OBD-II; Emissions Testing
  • General discussion of how OBD-II codes relate to emissions readiness and testing; included for broader context.
• Open Source code definition for P0968: Circuito do solenoidee C de controle de pressão - circuito aberto
  • Explicitly states P0968 corresponds to an open circuit in the Pressure Control Solenoid C circuit.
• Practical interpretation in the context of OBD-II
  • The combination of the above sources supports the interpretation that P0968, , is an electrical/open-circuit fault in solenoid C, which aligns with a common field diagnosis workflow for solenoid-related transmission codes.

In short

• P0968 with an open circuit interpretation points to an electrical fault in Pressure Control Solenoid C's circuit (wiring/connector, solenoid, or driver/ground issues). Start with a thorough wiring/connector inspection, verify power and ground to the solenoid, test the coil resistance, review live data for commanded vs. actual solenoid operation, and proceed to solenoid or TCM/PCM service as indicated by the findings. Confirm repairs with a road test and re-scan to ensure the code does not return.

This diagnostic guide was generated using verified reference data:

• Wikipedia Technical Articles: OBD-II
• Open-Source OBD2 Data: N/A (MIT)

Content synthesized from these sources to provide accurate, real-world diagnostic guidance.

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