Powertrain, shared range

P349E Cylinder 7 Deactivation/Intake Valve Performance

Check engine lightOn

EmissionsRelevant

Drive cycleRequired

Limp modeNo

P349E covers cylinder 7: deactivation was commanded, yet the cylinder kept its valve events. In GM's DFM design the intake lifter is unlocked first, while the exhaust lifter can only release once its cam lobe is back on the base circle; a sluggish pin therefore tends to leave the exhaust side working. GM's L84 and L87 check spots this through manifold pressure at each 90 degrees of crank rotation and stores a Type B code once 22 out of 25 opportunities have failed. Tula Technology, a specialist in skip-fire control, patented a check that combines intake pressure pulses with measured versus modelled crankshaft acceleration (US9891137B2). The wiring codes for cylinder 7 are P3449, P3451 and P3452. A driver may hear ticking and see the lamp.

Likely causes

Sluggish locking pin, mostly in the exhaust lifter of cylinder 7

Oil solenoid of cylinder 7 not opening fully

Low, thin or aerated oil

Symptoms

Ticking from the valve train
Check engine lamp on
Cylinder deactivation inhibited, higher consumption

Repair estimate

DifficultyHardWorkshop job

Parts and labour€100–4,500

Time0–14 h

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

Parts involved

liftervalve traincylinder deactivation solenoidengine oil

References: gsi.ext.gm.com, static.nhtsa.gov, patents.google.com.