Powertrain, shared range

P3428 Cylinder 4 Deactivation/Intake Valve Control Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

P3428 means the wire that switches cylinder 4's deactivation solenoid is tied to voltage. GM's bulletin 20-NA-038 lists cylinders 1, 4, 6 and 7 as the ones its AFM V8s switch to V4 mode, which makes cylinder 4 a standard candidate. In the 2019 documents for L84, L86 and the Corvette LT4, GM judges the circuit with the low-side stage switched on: a supply path of less than half an ohm counts as a short, and 20 bad results within 25 produce a Type B entry and the lamp after two trips. Because the low-side stage sinks the current, a line stuck at battery voltage can push the output into overcurrent, so after repair the module should be checked too. P3427 is the short to ground, P3425 the open. The truck or car keeps all cylinders running.

Likely causes

Cylinder 4 control wire shorted to a 12 V feed
Low-resistance winding in the cylinder 4 solenoid
Overloaded output stage in the engine control module

Symptoms

  • Check engine lamp on
  • No V4 or reduced-cylinder operation

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

P3425P3426P3427P3432P3420P3404

References: law.cornell.edu, gsi.ext.gm.com, gsi.ext.gm.com, static.nhtsa.gov.