Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
This code means there's a problem with one of the parts that helps your car change gears. It's like a switch that isn't working right.
The P0978 code indicates that the transmission control module (TCM) has detected a problem with the Shift Solenoid C's control circuit. This can mean the solenoid is not operating within its expected range or performance.
Shift solenoids are responsible for controlling the flow of transmission fluid to change gears. The 'C' solenoid is one of several in the transmission. The TCM monitors the electrical circuit of the solenoid and expects certain voltage readings. If the solenoid's performance is outside the expected range, the P0978 code is triggered.
• Transmission slipping
• Harsh or delayed shifting
• Illuminated check engine light
• Faulty Shift Solenoid C
• Wiring issues or poor electrical connections
• Malfunctioning transmission control module (TCM)
TCM: Transmission Control Module
Solenoid: An electromechanical device used to control fluid flow
• Scan the vehicle for codes and freeze frame data.
• Inspect the wiring and connectors to the shift solenoid.
• Test the shift solenoid's resistance and operation.
• Repair or replace damaged wiring or connectors.
• Replace the faulty shift solenoid C.
• Reprogram or replace the TCM if necessary.
• OBD-II scanner
• Multimeter
• Basic hand tools
$150 - $400
Moderate
• Honda Accord
• Toyota Camry
• Ford F-150
• Regular transmission fluid changes
• Routine vehicle maintenance
• Avoid aggressive driving habits
Transmission Performance Issue
• Avoid driving the vehicle until repaired to prevent further damage.
• Consult a professional mechanic for accurate diagnosis.
Check if the transmission or powertrain warranty covers solenoid issues.
P0978 is a common code for vehicles with automatic transmissions, often related to solenoid wear or electrical issues.
Moderate – Address promptly to avoid transmission damage.
Driving with transmission issues can lead to safety hazards and further damage.
• Vehicle at operating temperature
• Transmission in drive
Shift solenoids are located inside the transmission, often accessible by removing the transmission pan.
Q: Can I drive with a P0978 code?
A: It's not recommended as it can cause further transmission damage.
Q: How is a shift solenoid replaced?
A: The transmission pan is removed to access and replace the solenoid.
High-End · Full-system diagnostics
A full-system bidirectional platform aimed at advanced DIY users and professional diagnostic workflows.
Network faults often require full-system access instead of a generic code reader alone.
View on Amazon
Universal · Digital multimeter
A solid entry-level multimeter for voltage, continuity, resistance, and basic electrical troubleshooting.
Helpful for checking voltage drops, grounds, and basic circuit health when modules are not communicating.
View on Amazon
Universal · Wire connectors and repair kit
Useful when diagnosis points toward damaged wiring, corroded terminals, or connector repairs.
Useful if diagnosis points toward damaged connectors, wiring, or terminal repairs.
View on AmazonThese are optional diagnostic tools, not guaranteed fixes. As an Amazon Associate I earn from qualifying purchases.