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 deactivation or intake valve control circuit for cylinder 3. This system uses solenoids or actuators to disable intake valves during low-load conditions to improve fuel economy. A high voltage reading suggests a short to power, a faulty actuator, or a wiring issue. This can prevent proper valve operation, leading to reduced fuel efficiency, rough idle, or misfires.
1. Most Common Causes
- Short to battery voltage in the wiring harness of the cylinder 3 deactivation/valve solenoid
- Faulty cylinder 3 valve control/deactivation solenoid (open or internally shorted coil)
- Loose, corroded, or damaged connector at the solenoid or PCM
- Internal output driver failure in the PCM/ECM
- Mechanical issues with the deactivation lifter/tappet (sticking) causing electrical feedback
2. Symptoms You Will Notice
- Check Engine Light on
- Reduced fuel economy
- Rough idle or engine misfire
- Possible hesitation or lack of power
3. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
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 for voltage at the solenoid connector with key on; should be battery voltage. If high, check for short to power.
Step 4: Test the solenoid resistance; compare to specs. Replace if out of range.
Step 5: Clear code and test drive; if code returns, inspect PCM for faults.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances as it can cause reduced fuel economy and potential engine damage from misfires. Have it diagnosed promptly.
How much does it cost to fix?▼
Typically $50-$150 for diagnosis and repair, but if the solenoid needs replacement, parts and labor can range from $200-$400.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.