P3420
Moderate Severity (Level 3)Cylinder 3 Deactivation/Intake Valve Control Circuit High
P3420 usually means cylinder 3 Deactivation/Intake Valve Control Circuit High.
Can you still drive with P3420?
⚠️Short-distance driving is usually OK, but have this diagnosed within a week to prevent further damage.
Typical repair cost: $80 – $1200
Severity Level 3 — Moderate
This code indicates a moderate issue that may affect vehicle performance and fuel economy. Continued driving is possible in most cases, but prompt diagnosis and repair are recommended to prevent further damage.
Common Symptoms
- Engine performance reading abnormally high or staying at maximum
- Engine may run rich or have poor fuel economy (PCM sees faulty signal)
- Check Engine Light illuminated
- Diagnostic trouble code (DTC) stored in module memory
Possible Causes
- Failed engine sensor or actuator — internal short causing abnormally high voltage signal to the control module
- Wiring shorted to a 5V reference or 12V power wire in the same harness — wires melted together or chafing at a common point
- Poor ground connection for the powertrain/engine system — high resistance in ground path causes voltage to read high
- Faulty voltage regulator or power supply within the sensor
Common Fixes
- Scan vehicle with a professional-grade OBD2 scanner to read all stored codes and freeze frame data — note the conditions when the code set ($7-87 at shop, free at auto parts store for basic scan)
- Visually inspect the powertrain/engine system wiring harness and connectors — look for chafed wires, melted insulation, green corrosion, loose pins, or rodent damage (often free to check yourself, $120 diagnostic fee at shop)
- Test engine sensor or actuator with a multimeter at the connector — compare readings to factory service manual specs. If out of spec, replace engine sensor or actuator ($80-1200)
- Check the reference voltage supply to engine sensor or actuator — should be steady 5V (or 12V) — if low, trace back to PCM/BCM voltage regulator ($156-591 if module repair needed)
- Perform a voltage drop test on the ground side of the powertrain/engine system circuit — more than 0.1V drop means a bad ground that must be cleaned/repaired ($72-276 at shop)
Estimated Repair Cost
These are estimated costs based on generic repair data. Actual costs may vary depending on your vehicle, location, and labor rates.
Frequently Asked Questions
What does P3420 mean?
P3420 stands for "Cylinder 3 Deactivation/Intake Valve Control Circuit High". P3420 usually means cylinder 3 Deactivation/Intake Valve Control Circuit High.
Can you drive with P3420?
Short-distance driving is usually OK, but have this diagnosed within a week to prevent further damage.
How much does it cost to fix P3420?
Repair costs for P3420 typically range from $80 to $1200, depending on your vehicle make, model, and local labor rates. Common fixes include: Scan vehicle with a professional-grade OBD2 scanner to read all stored codes and freeze frame data — note the conditions when the code set ($7-87 at shop, free at auto parts store for basic scan); Visually inspect the powertrain/engine system wiring harness and connectors — look for chafed wires, melted insulation, green corrosion, loose pins, or rodent damage (often free to check yourself, $120 diagnostic fee at shop); Test engine sensor or actuator with a multimeter at the connector — compare readings to factory service manual specs. If out of spec, replace engine sensor or actuator ($80-1200).
Will P3420 clear itself?
Explore Repair Costs
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