P3493

Code

Generic P — Powertrain

Cylinder 12 Exhaust Valve Control Circuit/Open

Brand: Generic

Type: P — Powertrain

Views: UK: 20 EN: 39 RU: 28

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Page language: EN

Causes

Open or broken wiring in the exhaust valve control circuit for cylinder 12
Intermittent or poor connector contact (corrosion, bent pins) at the solenoid or harness
Faulty exhaust valve control solenoid/actuator on cylinder 12
Blown fuse or poor power/ground supply to the valve control bank
Short to voltage or ground in the harness
PCM/ECM driver failure (less common)

Symptoms

Check Engine Light (MIL) on
Possible misfire or rough running when cylinder 12 is affected
Reduced engine power or poor throttle response
Reduced fuel economy and increased emissions
Rough idle or vibration localized to cylinder 12 operation in some conditions

What to check

Read stored freeze frame and freeze data with a scan tool; note conditions when code set
Retrieve live data: exhaust/intake valve command status, cylinder 12 misfire counts, and PCM outputs
Visually inspect wiring harness and connector at cylinder 12 solenoid for damage, corrosion, or disconnection
Check related fuses and main power/ground points for the valve actuator bank
Measure solenoid resistance at the connector (with harness disconnected) and compare to factory spec
Back-probe the solenoid connector with engine running or while commanding the valve (use a scan tool) to observe voltage or PWM behavior

Signal parameters

Typical solenoid coil resistance: ~10–50 ohms (varies by design) — compare to vehicle spec
Control type: PCM supplies/controls a switched 12 V or ground with PWM (duty cycle varies with command)
Expected voltage: battery voltage at supply pin; switching pin will show 0–12 V or a PWM waveform when commanded
PWM frequency: often tens to a few hundred Hz (refer to manufacturer spec)
When circuit is open: no continuity between solenoid pins, no PWM or switching voltage present at the solenoid connector when commanded

Diagnostic algorithm

Confirm and record P3493, clear codes and perform a short drive cycle to verify the code returns. Note freeze frame/live conditions.
Visual inspection: check connector at cylinder 12 solenoid and wiring along the harness for damage, pins pushed out, corrosion, or water intrusion.
Check fuses and power/ground for the valve actuator bank. Repair any poor grounds or blown fuses.
With ignition off, disconnect the solenoid and measure coil resistance to ground and between pins. Compare to spec. Infinite/open or significantly out-of-spec resistance indicates a faulty solenoid or open wiring.
Reconnect and back-probe the connector. With a scan tool, command the exhaust valve and observe voltage/PWM at the control pin and battery voltage at the supply pin. No switching while commanded suggests open supply/driver or wiring break.
Perform a continuity check between the PCM connector pin and the solenoid connector pin to locate opens or shorts. Repair any damaged wiring and recheck.
If wiring and solenoid are good, swap the solenoid with another cylinder to see if the DTC follows the solenoid. If it follows the solenoid, replace the solenoid/actuator.
If the fault remains on cylinder 12 after a good solenoid and repaired wiring, suspect PCM driver fault and verify with manufacturer-specific tests before replacing the PCM.
Clear codes and perform full functional test/road test to confirm repair. Document and re-check for related codes.

Likely causes

Disconnected or corroded connector at cylinder 12 exhaust valve solenoid
Open wire (chafed, pinched, broken) in solenoid circuit for cylinder 12
Failed exhaust valve control solenoid/actuator at cylinder 12
Blown fuse or poor shared ground
PCM output driver fault (after wiring and actuator tests)

Fault status

⚠️ Status

PCM detected an open or abnormal condition in the exhaust valve control circuit for cylinder 12. The circuit did not respond to commanded operation and triggered a stored DTC.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.5 hours