Cylinder 8 Deactivation/Intake Valve Control Circuit Open
What does P3408 mean?
The P3408 code means the vehicle's onboard diagnostic system has detected: Cylinder 8 Deactivation/Intake Valve Control Circuit Open. This is a moderate severity code.
Common Symptoms
- Check Engine Light on
- Rough running at cruise speed
- Engine vibration during deactivation
- Tapping noise from cylinder 8
- Decreased fuel economy
Probable Causes (Ranked by Likelihood)
- Failed cylinder 8 deactivation solenoid Very High
- Open circuit in cylinder 8 solenoid wiring High
- Corroded connector at the solenoid Moderate
- ECM driver circuit fault Moderate
- Collapsed deactivation lifter on cylinder 8 Low
Step-by-Step Diagnostic Procedure
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Test cylinder 8 deactivation solenoid resistance
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Inspect solenoid wiring for open circuits
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Check connector for corrosion or damage
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Command the solenoid on/off with a scan tool
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Inspect lifter if solenoid tests good but deactivation fails
Frequently Asked Questions
Is P3408 only found on V8 engines?
Yes, cylinder 8 exists only on V8 (or larger) engines. This code is specific to the deactivation system on cylinder 8.
Can I disable the deactivation system to avoid these codes?
Yes, aftermarket AFM/MDS delete kits and tuners are available that disable the cylinder deactivation system. This eliminates the deactivation-related codes and potential lifter failures.
Are collapsed lifters a common problem?
Yes, particularly on GM V8 engines with AFM. Collapsed deactivation lifters are a well-known issue and can cause ticking noises, misfires, and check engine lights.