P3421Cylinder Deactivation (AFM/DoD)

Cylinder 2 Deactivation/Intake Valve Control Circuit/Open

P3421 indicates an open or malfunction in the cylinder 2 deactivation or intake valve control circuit on a GM AFM/DoD engine. Points to the cylinder 2 lifter oil manifold solenoid or its wiring.

🚗 Yes usually, but a stuck lifter risks valvetrain damage.
MEDIUM
severity
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🎯 Top Causes, Ranked by Likelihood

#1Cylinder 2 AFM solenoid open or failed$300-$700
40%
The lifter oil manifold solenoid for cylinder 2 is open or not responding.
#2Open or corroded wiring / connector$100-$300
30%
Break in the control circuit to the solenoid.
#3Stuck or collapsed cylinder 2 lifter$1200-$2500
20%
A failed deactivating lifter on cylinder 2.
#4Low oil pressure$50-$300
10%
Low oil pressure prevents lifter actuation.

🩺 Common Symptoms

💰 Repair Cost: DIY vs Shop

DIY Cost
$100-$700
Shop Cost
$300-$2500

📋 Free OBD2 Code Cheat Sheet

The 50 most common codes with likely cause and DIY fix cost. Sent once, no spam.

🔧 How to Diagnose P3421

1Check for cylinder 2 misfire codes
2Inspect the cylinder 2 solenoid connector and wiring
3Test solenoid resistance and command it with a scan tool
4Replace the solenoid or lifter as needed

❓ Frequently Asked Questions

What is P3421?
An open or fault in the cylinder 2 deactivation valve control circuit, typically the AFM solenoid or wiring.
Can a lifter cause P3421?
Yes, a stuck cylinder 2 AFM lifter can set it, usually with a tick and misfire.
How much to fix P3421?
Wiring or solenoid repair is a few hundred dollars; a lifter job runs $1500 or more.

🔗 Related Codes

P3400P3425P0302P0300
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