Powertrain, shared range

P3403 Cylinder 1 Deactivation/Intake Valve Control Circuit Low

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

The engine computer drives the deactivation valve for cylinder 1 through an output stage that checks its own wiring. P3403 means that check found the control line pulled to ground. GM documents it for the L84 and L86 V8s (2019): with the driver off, an impedance below 0.5 ohm to ground counts as a fault, and 20 failures in 25 samples taken every 250 ms set a Type B code, so the lamp comes on after the second trip. Ford's VDE monitor flags the same short via its smart driver within 5 seconds. An open line is P3401, a short to battery voltage P3404, a mechanical failure P3402. The engine then stays in all-cylinder mode, mainly costing fuel.

Likely causes

Control wire chafed against the engine and shorted to ground
Internal short in the cylinder 1 deactivation solenoid
Oil or water in the solenoid connector
Faulty output driver in the engine control module

Symptoms

  • Check engine lamp on after two trips
  • Engine no longer switches to reduced-cylinder mode
  • Somewhat higher fuel consumption

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

P3401P3402P3404P3407P3400

References: law.cornell.edu, gsi.ext.gm.com, gsi.ext.gm.com, fordservicecontent.com.