What Does P3421 Mean?
The PCM detected an open circuit or complete loss of continuity in the cylinder 3 exhaust valve control circuit. This prevents proper operation of the exhaust valve deactivation system for cylinder 3.
Common Causes
35%
Broken or disconnected wiring in exhaust valve control circuit
30%
Failed cylinder 3 exhaust valve control solenoid (internal open)
20%
Corroded or damaged electrical connector terminals
10%
Blown fuse or fusible link in solenoid power supply circuit
5%
PCM connector terminal damage or corrosion
Diagnostic Steps
1
Step 1: Check all fuses related to variable valve control system for continuity
2
Step 2: Inspect cylinder 3 exhaust valve solenoid connector for proper seating and terminal integrity
3
Step 3: Disconnect solenoid and measure resistance; infinite resistance confirms open solenoid
4
Step 4: Test continuity from PCM connector to solenoid connector on control circuit
5
Step 5: Inspect PCM connector terminals for pushed-back pins or corrosion
Estimated Repair Cost
$150 - $700
Parts + labor, varies by vehicle and location
The PCM detected an open circuit or complete loss of continuity in the cylinder 3 exhaust valve control circuit. This prevents proper operation of the exhaust valve deactivation system for cylinder 3.
The most common cause of P3421 (Cylinder 3 Exhaust Valve Control Circuit/Open) is: Broken or disconnected wiring in exhaust valve control circuit
Typical repair costs for P3421 range from $150 to $700, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to drive but fuel economy and emissions will be negatively impacted. Cylinder deactivation will not function properly.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P3421 to identify the root cause.
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Quick Info
Category
Powertrain
System
Variable Valve Timing/Cylinder Deactivation System
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
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