Symptoms:

• The exhaust back pressure regulator will be disabled, in either a closed or open position
• Reduced engine performance and insufficient turbocharger pressure
• The check engine warning light with be illuminated

Causes:

• Damaged electrical wiring and connectors
• Shorted or open exhaust back pressure sensor harness
• Faulty PCM, in very rare cases

Possible Solutions:

• Clearing or replacing a clogged back pressure tube
• Replacing or cleaning a faulty exhaust back pressure sensor
• Replacing or repairing a shorted or open exhaust back pressure sensor
• Manually test individual circuits within the exhaust back pressure system, and replace any faulty components
• In rare cases, replacing a faulty PCM