Powertrain, shared range

P3408 Cylinder 1 Exhaust Valve Control Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

If an engine has its own actuator for the exhaust valves of cylinder 1, P3408 marks a control circuit that reads high, usually a short to battery voltage. No manufacturer documents this code publicly. For comparison, GM checks the intake-side P3404 with the driver switched on and flags under 0.5 ohm to supply. A GM patent application switches intake and exhaust valves together through one shared hydraulic valve, exhaust side first, and describes no separate exhaust channel either. With one solenoid per cylinder, as on GM's DFM, the code is not needed. Siblings: P3405 open, P3406 function, P3407 short to ground; P3404 is the intake-side equivalent.

Likely causes

Control wire shorted to a supply voltage
Shorted coil in the exhaust valve actuator
Output stage fault in the engine control module

Symptoms

  • Check engine lamp on
  • Cylinder deactivation disabled

Repair estimate

DifficultyMediumDIY possible
Parts and labour€60–900
Time0.5–4 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

cylinder deactivation solenoidwiring harnessecm

Related codes

P3405P3406P3407P3404P3400

References: law.cornell.edu, gsi.ext.gm.com, patents.google.com.