P3490

Code

Generic P — Powertrain

Cylinder 12 Deactivation/Intake Valve Control Circuit Performance

Brand: Generic

Type: P — Powertrain

Views: UK: 21 EN: 36 RU: 25

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Page language: EN

Causes

Open or shorted wiring to cylinder 12 deactivation/valve control solenoid
Corroded, loose or damaged connector at the solenoid or PCM
Failed deactivation solenoid/actuator (stuck or electrically failed)
Low engine oil pressure, contaminated oil, or incorrect oil level affecting actuation
Internal valve deactivation mechanism jammed or mechanically stuck
Faulty PCM or driver circuit

Symptoms

Malfunction indicator lamp (MIL) illuminated
Rough idle or vibration from engine due to cylinder behavior change
Reduced fuel economy (if cylinder deactivation not functioning)
Possible engine power reduction or limp-home behavior
Audible valvetrain noise or irregular ticking if a valve is stuck

What to check

Scan for freeze frame and related codes; note conditions when code set
Check engine oil level and condition (contamination, viscosity)
Visual inspection of wiring harness and connectors at cylinder 12 solenoid and PCM
Backprobe connector and measure supply voltage, ground and command signal with ignition on and while commanding the circuit
Measure resistance of the solenoid/actuator coil (compare to spec) and check for short to ground/short to battery
Use a scan tool to command the cylinder 12 deactivation/valve actuator on/off and watch live data/response

Signal parameters

Supply voltage to solenoid: ~12 V (battery voltage) with ignition ON (spec may vary)
Command signal: PWM or switched ground from PCM; duty cycle 0–100% or on/off depending on system
Solenoid coil resistance: typically low ohms (example 6–30 Ω) — consult OEM spec
Expected current draw: typically under a few amps when energized (spec dependent)
Circuit continuity: near zero ohms from solenoid to PCM driver pin; infinite/open = open circuit

Diagnostic algorithm

Retrieve stored data (freeze frame, pending codes) and clear the code. Test-drive to see if code returns and note conditions.
Perform a visual inspection of the cylinder 12 solenoid harness and connector. Repair any physical damage, corrosion, or loose terminals.
Check engine oil level and condition; change oil if severely contaminated or outside spec, then retest.
With connector disconnected, measure solenoid coil resistance. Compare to OEM spec; replace if out of range or open/shorted.
Reconnect and backprobe connector. With ignition ON, verify supply voltage and ground presence. With a scan tool, command the actuator and observe command voltage/PWM and solenoid response.
Perform voltage drop tests on supply and ground circuits while commanding the solenoid to detect high resistance connections.
Check for shorts: measure resistance from the command pin to battery and ground to detect unintended short circuits.
Swap the solenoid/actuator with a known-good cylinder (if identical and allowed) to isolate component vs. wiring/PCM.
If wiring and solenoid check good but commands not seen or driver behaves erratically, inspect PCM connector pins for damage and consider PCM/driver testing per OEM procedures.
After repairs or replacements, clear codes and verify proper operation over varied conditions.

Likely causes

Faulty or intermittently failing solenoid for cylinder 12
Wire chafe causing intermittent short to ground or battery
Poor connector contact (corrosion/water intrusion)
Low/dirty oil preventing hydraulic actuation
PCM driver output degraded or damaged (less common)

Fault status

⚠️ Status

Cylinder 12 Deactivation/Intake Valve Control Circuit Performance — commanded actuator response did not match expected response; electrical or mechanical fault possible.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.5-3.0 hours