Powertrain, generic (extended)

P2656 "A" Rocker Arm Actuator System Performance/Stuck Off (Bank 2)

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

For bank 2, P2656 reports that actuator A was told to switch the rocker arms but the expected change in valve lift did not show up, or it was too small. Since such engines give every bank a separate oil feed and solenoid, a clogged screen or sticking spool on that side alone is enough. No manufacturer publishes P2656; GM's bank 1 test (P2646 in 15OBDG05) shows the usual method: an intrusive lift toggle at moderate load and warm oil, judged by oil-pressure ripple. CARB permits two-step systems to flag faults only once emissions exceed the threshold, but every such failure must then be caught. Low oil level, wrong viscosity and sludge deserve the first look.

Likely causes

Low, wrong or sludged engine oil
Clogged oil screen or sticking spool at the bank 2 solenoid
Seized locking pin in a bank 2 rocker arm

Symptoms

  • MIL on after a completed test
  • Weaker response at higher engine speed
  • Higher fuel consumption

Repair estimate

DifficultyMediumDIY possible
Parts and labour€50–900
Time0.5–3.5 h

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

Parts involved

rocker arm actuator a b2oil control valveoil supply

Related codes

P2657P2655P2646P2661

References: law.cornell.edu, gsi.ext.gm.com, en.wikipedia.org.