OBD II Fault Code

  • OBD II P3478

OBD-II Code Decreased engine performance is defined as a Cylinder 10 Exhaust Valve Control Circuit Performance

In an effort to meet fuel and emissions standards, many manufacturers are utilizing cylinder deactivation systems. This system allows the engine's control module (PCM) to disable select cylinders when additional power is not needed from the engine, such as at idle or when cruising on the highway. If the engine's control module (PCM) determines that the Exhaust Valve for cylinder number ten is not Turning on or off the way it is being commanded, the PCM will set code P3478.

Decreased engine performance Symptoms

  • Decreased engine performance
  • Increased fuel consumption

Common Problems That Trigger the P3478 Code

  • Engine oil level is too low
  • Powertrain Control Module (PCM) failure
  • Variable valve timing solenoid failure
  • Wiring issue
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