What it means
Shift solenoid C shows intermittent electrical or hydraulic dropouts — vibration, loose connector, ATF contamination or thermal sensitivity. Hard to reproduce on a static bench check.
At a glance
- Usually lights the check-engine light
How it works
Shift Solenoid C switches hydraulic flow for gear changes, and the TCM monitors its electrical circuit and transmission response while driving. P0764 sets when Solenoid C operation or its circuit signal is intermittent, so a loose connection, vibration, heat, or a hydraulic dropout may make the response erratic rather than consistently failed.
Common causes
Most likely first.
- Loose connector at the transmission
- Hot-soak intermittent
- Connector with intermittent contact under vibration
Symptoms
- Check engine or transmission warning light on
- Harsh, delayed, or missing shifts
- Possible limp mode (locked in one gear)
- Slipping or shuddering during gear changes
How to diagnose it
- Record freeze-frame data and scan for related transmission codes, noting the temperature, gear, and driving conditions associated with the Solenoid C dropout.
- Inspect the transmission connector and Solenoid C wiring for loose terminals, corrosion, fluid intrusion, chafing, or routing that allows vibration against nearby parts.
- Check fluid level and condition, since contamination or degraded fluid can contribute to intermittent sticking of Solenoid C.
- Use scan-tool data during a controlled drive to watch Solenoid C command and transmission response as the fault conditions are reproduced.
- Perform the manufacturer’s harness wiggle, continuity, and solenoid tests under the temperature or vibration conditions associated with the fault.
Common fixes
- Secure the transmission connector and repair loose or corroded terminals.
- Repair chafed wiring or reroute and secure a harness that contacts a vibrating component.
- Service contaminated or degraded fluid as specified for the transmission.
- Replace Shift Solenoid C if it intermittently fails the specified electrical or functional test.
- Repair a sticking hydraulic passage if testing confirms intermittent flow restriction.
Can I keep driving?
Keep trips short and avoid high loads if shifts are unpredictable; stop if the transmission slips or loses drive. An intermittent Solenoid C fault can become persistent and may lead to overheating or further transmission wear.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.