P3402
System
Powertrain (Engine)
Scanner required
Full-system scanner (engine, ABS, SRS, transmission, service resets)

Cylinder 2 Deactivation System Performance

Understand P3402, common causes, and the right SEAFLO pump to diagnose it.

Active Fuel Management (AFM/DOD) system cannot deactivate or reactivate cylinder 2 as commanded — common on GM V6/V8 with cylinder deactivation.

Common symptoms

  • Ticking or misfire on affected cylinder
  • P0302 may accompany
  • Rough idle
  • Check engine light
  • Reduced fuel economy benefit lost

Typical causes

  • Failed AFM lifter on cylinder 2
  • Low oil pressure to AFM solenoids
  • Wrong oil viscosity or low oil level
  • AFM solenoid oil passage blockage
  • Collapsed AFM lifter on cylinder 2

What scanner do you need?

Full-system scanner (engine, ABS, SRS, transmission, service resets)

Use live data and freeze frame to confirm the fault before replacing parts. ABS, SRS, and network U-codes usually require a full-system scanner.

Diagnostic tips

  • Record freeze frame data when the code first sets
  • Clear the code only after fixing the root cause
  • Check for related pending codes that point to a common issue
  • Verify battery voltage is above 12.4V before chasing sensor codes

Frequently asked questions

Can I diagnose P3402 with a basic code reader?
P3402 may set in the engine module, but related diagnostics often benefit from an enhanced or full-system scanner with live data and freeze frame.
Is it safe to drive with P3402?
It depends on the code and symptoms. Flashing check engine lights and misfire codes should be addressed immediately. Consult a professional if unsure.