Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
This code means that the car's computer found a problem with the system that controls how one of the engine's parts (the intake valve for cylinder 3) turns on and off. It's like a switch that isn't working right.
The P3420 code indicates an issue with the electrical circuit responsible for controlling the deactivation of the intake valve on cylinder 3. The circuit is reading a voltage that is too high.
P3420 is triggered when the Engine Control Module (ECM) detects a high voltage condition in the intake valve control circuit for cylinder 3. This could be due to a malfunctioning solenoid, a wiring issue, or a problem with the ECM itself.
• Check Engine Light is on
• Reduced engine performance
• Engine misfire or rough idle
• Faulty intake valve control solenoid
• Wiring issues or poor connections in the circuit
• Malfunctioning ECM
ECM: Engine Control Module
Solenoid: An electromechanical device used to control a valve
• Use an OBD-II scanner to confirm the code.
• Inspect the wiring and connectors for damage or corrosion.
• Test the intake valve control solenoid for proper operation.
• Replace the intake valve control solenoid if faulty.
• Repair or replace damaged wiring or connectors.
• Reprogram or replace the ECM if necessary.
• OBD-II scanner
• Multimeter
• Socket set
$150 - $500
Moderate
• Honda Accord
• Chevrolet Silverado
• GMC Sierra
• Regular maintenance checks on wiring and connectors
• Use quality fuel to prevent deposits
• Routine engine inspections
Engine Performance
• Don't ignore the Check Engine Light.
• Get the vehicle inspected by a professional as soon as possible.
Check with the vehicle manufacturer for warranty coverage on engine components.
P3420 is a code that has been associated with vehicles using cylinder deactivation technology, which became more common in the 2000s.
Moderate – It's important to address this issue to prevent further engine performance problems.
Driving with this code may lead to reduced engine efficiency and increased emissions.
• Engine at operating temperature
• Vehicle in a safe and stationary position
The intake valve control solenoid for cylinder 3 is typically located on or near the engine cylinder head.
Q: Can I drive with a P3420 code?
A: It's not recommended to drive for long periods with this code as it can lead to further engine issues.
Q: How can I reset the P3420 code?
A: You can clear 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.
Fitment Required · Vehicle-fitment part
Commonly relevant for misfire, ignition-efficiency, and some drivability-related repairs.
Misfire and ignition-related faults commonly involve spark plugs as part of the repair path.
Check the correct plug type, gap, and engine application for your vehicle.
View options on Amazon
Fitment Required · Vehicle-fitment part
Relevant when the fault points toward ignition-coil performance or cylinder-specific ignition issues.
Some ignition faults involve coil performance or cylinder-specific coil problems.
Match the coil to your engine and confirm the failed component before ordering.
View options on AmazonThese parts may be related to this fault category, but a code by itself does not confirm exact fitment or guarantee that replacing a part will solve the problem.