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 has found a problem with the wires or signals that control the exhaust valve for cylinder number 3. It's like a broken switch in a toy that makes it stop working.
The engine control module (ECM) monitors the exhaust valve control circuit for each cylinder. If it detects an open circuit or a problem in the control circuit for cylinder 3, it triggers the P3421 code.
The P3421 code indicates that the ECM has detected an open circuit or malfunction in the exhaust valve control circuit for cylinder 3. This can affect the variable valve timing, leading to performance issues.
• Check Engine Light is on
• Reduced engine performance
• Engine misfire or rough idle
• Decreased fuel efficiency
• Faulty exhaust valve control solenoid
• Open or shorted wiring in the exhaust valve control circuit
• Poor electrical connection in the circuit
• Faulty ECM
ECM: Engine Control Module, the computer that controls engine functions.
Solenoid: An electromechanical device used to control a valve.
• Use an OBD-II scanner to confirm the code.
• Inspect the wiring and connectors for cylinder 3 exhaust valve control circuit.
• Test the exhaust valve control solenoid for proper operation.
• Check the ECM for faults.
• Repair or replace damaged wiring or connectors.
• Replace the faulty exhaust valve control solenoid.
• Reprogram or replace the ECM if necessary.
• OBD-II scanner
• Multimeter
• Basic hand tools
$150 - $500
Moderate
• Chevrolet Silverado
• GMC Sierra
• Cadillac Escalade
• Regular maintenance and inspection of wiring and connectors.
• Timely replacement of faulty components.
• Use high-quality replacement parts.
Engine Performance
• Do not ignore the Check Engine Light.
• Seek professional diagnosis if unsure.
• Avoid driving aggressively until repaired.
Check if the vehicle is still under warranty for powertrain components.
This code is commonly associated with vehicles that have variable valve timing systems and has been reported in models with higher mileage.
Moderate – Address the issue soon to avoid potential engine damage.
Driving with a malfunctioning exhaust valve can lead to increased emissions and potential safety issues.
• Engine at operating temperature
• Vehicle stationary
The exhaust valve control solenoid for cylinder 3 is typically located on or near the cylinder head.
Q: Can I drive with a P3421 code?
A: It's not recommended to drive for extended periods with this code, as it can lead to performance issues and potential engine damage.
Q: How can I reset the P3421 code?
A: You can reset the code using an OBD-II scanner, but it's important to fix the underlying issue first.
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Universal · Digital multimeter
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Useful when diagnosis points toward damaged wiring, corroded terminals, or connector repairs.
Useful if diagnosis points toward damaged connectors, wiring, or terminal repairs.
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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.
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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.