Cylinder 3 Deactivation/Intake Valve Control Circuit High
The P3420 code indicates that the powertrain control module (PCM) has detected a high voltage condition in the cylinder 3 deactivation/intake valve control circuit. This circuit is part of the cylinder deactivation system (also known as Active Fuel Management or Displacement on Demand) used to improve fuel economy by shutting down cylinders under light load. A high voltage reading suggests a short to power, a faulty actuator, or a wiring issue.
01. Most Common Causes
- Short to voltage in the wiring harness of cylinder 3 deactivation solenoid
- Faulty cylinder 3 deactivation solenoid (stuck open or shorted internally)
- Corroded or damaged connector at the solenoid or PCM
- Failed PCM (rare)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Reduced fuel economy
- Engine misfire or rough idle
- Loss of power or hesitation during acceleration
03. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data. Clear code and test drive to see if it returns.
Step 2: Visually inspect the wiring and connector for cylinder 3 deactivation solenoid for damage, corrosion, or shorts.
Step 3: Use a multimeter to check the solenoid resistance (typically 20-30 ohms) and compare to specifications.
Step 4: Check for voltage at the solenoid connector with key on; should be battery voltage on one pin and a ground signal from PCM on the other. If voltage is high or missing, trace circuit.
Step 5: If wiring and solenoid are good, suspect PCM fault; perform a PCM test or reprogramming if necessary.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances with this code, as it can cause engine misfire, reduced fuel economy, and potential damage to the catalytic converter. Have it diagnosed promptly.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for diagnosis and repair, depending on whether it's a simple wiring fix or solenoid replacement. Parts cost around $30-$80 for the solenoid.