What Does P3494 Mean?
The PCM detected that cylinder 12's exhaust valve control system is not responding correctly to commands. The valve timing or deactivation is not matching expected performance parameters.
Common Causes
35%
Mechanical failure of exhaust valve lifter or locking pin mechanism
30%
Low or contaminated engine oil affecting hydraulic operation
20%
Weak or sticking exhaust valve control solenoid
10%
Blocked oil passages to cylinder 12 valve mechanism
5%
Worn camshaft lobe or rocker arm
Diagnostic Steps
1
Step 1: Check engine oil level and condition; verify proper viscosity oil is being used and oil is not contaminated
2
Step 2: Monitor exhaust valve control solenoid operation with scan tool while commanding activation/deactivation
3
Step 3: Measure oil pressure at idle and operating temperature to ensure adequate hydraulic pressure
4
Step 4: Remove valve cover and inspect cylinder 12 lifter mechanism for proper operation and damage
5
Step 5: Test solenoid flow rate and check for restrictions in oil supply passages
Estimated Repair Cost
$300 - $1,500
Parts + labor, varies by vehicle and location
The PCM detected that cylinder 12's exhaust valve control system is not responding correctly to commands. The valve timing or deactivation is not matching expected performance parameters.
The most common cause of P3494 (Cylinder 12 Exhaust Valve Control Circuit Performance) is: Mechanical failure of exhaust valve lifter or locking pin mechanism
Typical repair costs for P3494 range from $300 to $1,500, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle is safe to drive but may experience rough idle, reduced performance, and poor fuel economy. Extended driving may cause additional engine wear.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P3494 to identify the root cause.
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Quick Info
Category
Powertrain
System
Variable Valve Timing/Cylinder Deactivation
Difficulty
Type
Generic (SAE)
Recommended Tools
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