Powertrain, generic (extended)

P2657 "A" Rocker Arm Actuator System Stuck On (Bank 2)

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

P2657 is the stuck-on case for bank 2: actuator A keeps the rocker arms of the second bank in their switched mode after the controller has asked for the base setting. On a cylinder deactivation design that could mean valves stay closed on that side; on a two-step design the high-lift profile stays active at idle. No manufacturer documents P2657 publicly; GM's bank 1 test P2647 (2015, 15OBDG05) shows the principle, flagging a pressure ripple below its limit during a deliberate toggle. A solenoid that leaks oil when off, a jammed locking pin or debris in the oil passage of that bank are candidates. Misfires on one bank and a lumpy idle are typical.

Likely causes

Bank 2 solenoid passing oil while switched off
Locking pin stuck in the engaged position
Debris in the bank 2 oil passage

Symptoms

  • Misfire codes on bank 2 cylinders
  • Lumpy idle
  • Poor low-speed driveability

Repair estimate

DifficultyMediumDIY possible
Parts and labour€60–900
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 valve

Related codes

P2656P2655P2647P2662

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