DIAGNOSIS AND TESTING

TURBOCHARGER BOOST PRESSURE

Low turbocharger boost pressure can cause poor engine performance and driveability concerns. The following procedure will test the turbocharger boost pressure.

Causes of low boost pressure include the following:

• Restricted air inlet system
• Leak in charge air cooler system
• Restricted/high pressure drop across charge air cooler
• Damaged turbocharger compressor wheel housing
• Turbocharger wastegate stuck open
• Excessive exhaust restriction

Causes of excessively high boost pressure include:

• Turbocharger wastegate stuck closed
• Turbocharger wastegate signal line leaking or damaged
• Damaged wastegate command valve O-rings
• Wastegate command valve mechanically stuck in actuated position

Several Diagnostic Trouble Codes (DTCs) can be set that will indicate high or low system boost levels. There is a DTC for circuit faults relating to the electronically controlled wastegate command valve.

(Refer to 11 - EXHAUST SYSTEM/TURBOCHARGER SYSTEM/CHARGE AIR COOLER AND PLUMBING - DIAGNOSIS AND TESTING) for diagnosing of low or high boost pressure due to leaks.