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Error Code P0968 is defined as Pressure Control Solenoid “C” Control Circuit/Open. This is a generic trouble code, meaning it applies to all vehicles equipped with the OBD-II system, especially those made since 1996 up to the present. It also only appears in vehicles with automatic transmission. This may include but is not limited to vehicles from Acura, BMW, Chevrolet, Ford, GMC, Honda, Land Rover, Nissan, and Saturn. While generic, specifications on the definition, troubleshooting, and actual repair may vary depending on the vehicle’s year, make, model, and powertrain configuration.
In most cases, the automatic transmission will have at least three pressure control solenoids called Solenoids A, B, and C. Newer transmission models have more gears and solenoids.
Other error codes associated with this one include:
- Error Code P0969
- Error Code P0970
- Error Code P0971
When this code is detected, it means the vehicle’s powertrain control module (PCM) has detected a problem in the transmission pressure control solenoid “C” control circuit.
The automatic transmission is controlled by bands and clutches that change gears with the help of fluid pressure activated at the right place, at the right time. The transmission pressure control solenoid’s job is to adjust the fluid’s pressure for the automatic transmission to work properly and shift smoothly. The PCM monitors the pressure in the solenoid and directs fluid to various hydraulic circuits, which change transmission gear at the precise ratio as needed.
When error code P0968 appears, that means the “C” pressure control solenoid control circuit is open.
- Increased fuel consumption
- Overheating transmission
- Slipping transmission (when shifting)
- Hard shifting (transmission bangs into gear)
- Misfire-like symptoms
- PCM puts the transmission into limp-mode
- Faulty pressure control solenoid
- Dirty (contaminated) transmission fluid
- Blocked transmission filter
- Faulty transmission pump
- Faulty transmission valve body
- Blocked hydraulic passages
- Corroded or damaged connector
- Faulty or damaged wiring
- Defective PCM (rare)
Before starting the diagnosis process, start researching for the Technical Service Bulletin (TSB) for the specific vehicle (year, model, and transmission). In many cases, this can save you a lot of time by pointing you in the right direction of diagnosis and repair.
Fluid and Wiring Check
First, make sure the fluid level is at the right level and condition. Then, before changing the fluid, check the records of the vehicle, verify the last oil and filter change.
Next, make sure you thoroughly check all wirings. Look for noticeable signs of damage, defects, and wear and tear. Check all the connectors for possible signs of corrosion. Check the damaged pins and security as well. All wires and connectors to the transmission pressure control solenoids must be checked, including the transmission pump.
Based on the vehicle’s specific configuration, the vehicle’s transmission may be driven mechanically or electronically.
Advanced diagnosis largely depends on the specifics of the vehicle and requires special equipment for accurate diagnosis, including multimeter and technical reference specific for the vehicle.
Subsequently, voltage requirements depend on the vehicle’s specific model. Fluid pressure requirements also vary based on the design and configuration of the transmission.
The normal readings for the connections and wirings for the vehicle are at 0 ohms of resistance unless specified in the technical data. Nevertheless, it is always necessary to conduct continuity with the power removed from the circuits to avoid shorting the circuit and causing damage. No continuity or resistance means faults in wiring are caused by open or shorted and must be repaired, if not replaced.
How to Fix
Common repairs for this code include:
- Repair or replacement of faulty pressure control solenoid
- Repair or replacement of faulty transmission pump
- Repair or replacement of faulty transmission valve body
- Changing fluid and filter
- Flushing of the transmission to clean the passages
- Cleaning connectors off of corrosions
- Repair or replacement of faulty wires
- Flashing or replacement of PCM
This code is a serious problem and must be addressed as soon as possible to avoid significant damage to the transmission.
Possible misdiagnosis for this code includes engine misfire problems, internal transmission problems, transmission pump malfunction, and driveline issues.