Powertrain, generic (extended)

P2648 "A" Rocker Arm Actuator Control Circuit Low (Bank 1)

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P2648 points to a low-side electrical fault on the control line of rocker arm actuator A, bank 1: the line reads low, typically a short to ground or a solenoid with shorted turns. GM's 2015 table 15OBDG05 tests the driver for short-to-ground faults with ignition in crank or run and more than 11 V, trips after 100 bad samples out of 120 and lights the MIL at once (Type A). In GM's 2004 table for the Honda-made L66 V6 of 3.5 litres, the controller expects a return signal whenever it energises the VTEC solenoid; 0 V for 2 s sets the code. Check for chafed wiring against the head, a wet connector or a failed solenoid. Without switching the engine runs only in base lift.

Likely causes

Control wire chafed through to ground
Shorted turns in the solenoid winding
Moisture or oil bridging pins in the connector

Symptoms

  • MIL on immediately
  • No switching to the second lift stage
  • Reduced top-end power

Repair estimate

DifficultyMediumDIY possible
Parts and labour€60–400
Time0.5–2 h

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

Parts involved

rocker arm actuator a b1oil control valvewiring harness

Related codes

P2645P2649P2658P2653

References: gsi.ext.gm.com, gsi.ext.gm.com, law.cornell.edu.