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 helps control the exhaust valves on one side of the engine. It's like when a switch doesn't work to turn a light on or off.
The P0078 code indicates an issue with the electrical circuit that controls the exhaust valve solenoid for the first bank of the engine.
The exhaust valve control solenoid is responsible for regulating the timing of the exhaust valves in the engine. This code is triggered when the engine control module (ECM) detects a malfunction in the solenoid's circuit on bank 1, which is the side of the engine with cylinder 1.
• Check Engine Light is on
• Poor engine performance
• Increased fuel consumption
• Faulty exhaust valve control solenoid
• Wiring issues such as open or short circuits
• Faulty ECM
Solenoid: A coil of wire acting as a magnet when carrying electric current.
ECM: Engine Control Module, the computer that controls engine functions.
• Scan the vehicle for codes and freeze frame data.
• Inspect the wiring and connectors for damage or corrosion.
• Test the exhaust valve control solenoid for proper operation.
• Replace the exhaust valve control solenoid if faulty.
• Repair or replace damaged wiring or connectors.
• Reprogram or replace the ECM if necessary.
• OBD-II scanner
• Multimeter
• Basic hand tools
$150 - $400
Moderate
• Honda Accord
• Toyota Camry
• Ford F-150
• Regularly inspect and maintain engine wiring.
• Perform routine engine diagnostics.
• Keep the engine control module updated.
Engine Performance
• Have the vehicle inspected by a professional mechanic.
• Avoid driving the vehicle until the issue is resolved to prevent further damage.
Check if the vehicle's powertrain warranty covers this repair.
This code has been reported in vehicles with higher mileage or those that have not been regularly maintained.
Moderate – It should be addressed soon to avoid potential engine damage.
Ignoring this code may lead to increased emissions and potential engine damage.
• Engine at operating temperature
• Vehicle stationary
The exhaust valve control solenoid is typically located near the cylinder head on bank 1 of the engine.
Q: Can I drive with a P0078 code?
A: It's not recommended to drive for extended periods with this code, as it may lead to engine damage.
Q: How do I reset the P0078 code?
A: After repairs, the code can be reset using an OBD-II scanner, but it will return if the underlying issue is not fixed.
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.