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 the part of the car that tells the transmission how to shift gears. It's like when a toy remote control car doesn't change directions because the button is stuck.
The P078F code is triggered when the Transmission Control Module (TCM) detects an issue with the circuit related to the transmission mode switch 'C'.
The P078F code indicates a malfunction in the electrical circuit of the transmission mode switch 'C'. This switch is responsible for sending signals to the TCM to control the transmission's shifting patterns. A fault in this circuit can lead to improper or erratic shifting.
• Erratic or harsh shifting
• Transmission stuck in one gear
• Check Engine Light is on
• Faulty transmission mode switch
• Damaged wiring or connectors
• Faulty Transmission Control Module (TCM)
Transmission Control Module (TCM): A computer that controls the transmission's functions.
Circuit: A path for electrical current to flow.
• Scan the vehicle for additional codes.
• Inspect the wiring and connectors related to the transmission mode switch.
• Test the transmission mode switch for proper operation.
• Replace the faulty transmission mode switch.
• Repair or replace damaged wiring or connectors.
• Reprogram or replace the TCM if necessary.
• OBD-II scanner
• Multimeter
• Screwdriver set
$150 - $500
Moderate
• Ford F-150
• Chevrolet Silverado
• Toyota Camry
• Regularly inspect and maintain transmission components.
• Keep the transmission fluid clean and at the proper level.
• Avoid aggressive driving habits.
Transmission Control Issue
• Have the vehicle inspected by a professional mechanic.
• Avoid driving the vehicle if the transmission is not shifting properly.
Transmission components may be covered under the powertrain warranty. Check with your vehicle manufacturer.
P078F is a relatively uncommon code, typically associated with modern vehicles with advanced transmission control systems.
Moderate – Address the issue soon to prevent further transmission damage.
Driving with a malfunctioning transmission can lead to unsafe driving conditions. Address the issue promptly.
• Vehicle engine running
• Transmission in various gears
The transmission mode switch is typically located on or near the transmission housing.
Q: Can I drive with a P078F code?
A: It's not recommended to drive with this code as it can lead to further transmission damage.
Q: How can I reset the P078F code?
A: You can reset the code with an OBD-II scanner, but it's important to fix the underlying issue first.
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.