P340C: Deactivation/Exhaust Valve Control Circuit Bank 1

What does P340C mean?

Generic electrical fault on the cylinder deactivation/exhaust valve control circuit on bank 1. On engines with cylinder deactivation the exhaust valves of a switched-off cylinder are held closed together with its intake valves, typically by switchable rocker arms or lifters that oil-pressure solenoids control; this code covers the bank's control circuit for the exhaust-side actuators. While it is faulty the module stops deactivating cylinders on that bank, so the engine runs on all cylinders and uses slightly more fuel.

The code tells you which monitor failed, not which part is broken. Test before replacing parts.

Symptoms

• Check engine light on
• Cylinder deactivation inactive, slightly higher fuel consumption

Common causes

• High Deactivation solenoid failed
• Medium Wiring break or unplugged connector

Likelihood is a general estimate across vehicles; your make and model may differ.