Turbocharger: Testing and Inspection

TURBOCHARGER

The turbocharger, charge air cooler and exhaust gas recirculation systems operate with one another and must be tested as a complete system. It is important that all components of the air intake system be thoroughly tested any time a symptom is present for one of these components.


It is typical to notice a small amount of engine oil in the air intake system. This comes from the crankcase ventilation and may weep out of hose connections that are not clamped properly. This does not mean that the turbocharger requires replacement.


If DTC's or the performance of the vehicle lead to the determination that the boost pressure and/or mass air flow values are out of range, the systems listed should be inspected.


NOTE: Also a continuous air leak may result in an intermittent symptom. The ECM monitors the sensor readings continuously but only sets a DTC or reduces the engine torque when these readings are outside of the tolerances, which may occur under certain driving conditions.

Inspect the following:

- Air intake system plumbing: Loose or broken hoses or fittings may create an air leak resulting in a loss of pressure and mass air flow. (A smoke machine does not create enough pressure to find a leak in the air intake system).
- Turbo Resonator: Inspect the resonator (muffler, connected to the turbocharger) for air leaks at the seam between the two shells.
- Charge Air Cooler: A charge air cooler damaged by tools or external debris may leak air.
- Exhaust Gas Recirculation (EGR) valve: A sticking EGR valve influences the mass air flow causing implausibility with MAF, which displays one or more DTC's. Don't replace the EGR valve if no DTC's are present. Use the actuator test in DRBIII(R) to move the EGR valve at idle speed. The MAF value should alternate between 500 to 600 mg/strk at 5% ratio (almost closed) and 200 to 300 mg/strk at 95% ratio (almost opened) when the "EGR Positioner" is being actuated by DRBIII(R).
- Mass Air Flow Sensor (MAF): The mass air flow, measured and provided by the MAF is critical for calculations performed by the ECM and may result in several DTC’s related to the air intake system if not accurate.
- Boost Pressure Sensor.
- Turbocharger: See TURBOCHARGER DIAGNOSTIC PROCEDURE. Consider that an operating turbocharger creates a flow sound, which is normal and does not require replacement. Other sounds like whistling are potentially caused by the resonator or improper line connections.

TURBOCHARGER DIAGNOSTIC PROCEDURE

1. Visually inspect all the blades of the turbocharger compressor and turbine wheel for damage which may have been caused by foreign particles. For example if the air filter was improperly installed or an incorrect air filter was installed.
2. Start the engine and let it run at idle speed. Perform the actuator test using the scan tool. The connecting rod of the actuator should move back and forth when the "Boost Pressure Sol" is being actuated by scan tool in short intervals. Also note that the values for both MAF and Boost Pressure should alternate slightly if both sensors work properly.

CAUTION: Do NOT try to move the actuator mechanism by pushing or pulling the connecting rod. There is a worm gear attached to the actuator mechanism, which doesn't allow any movement from its output side.

3. If the actuator mechanism doesn't move at all check power and ground supply of the actuator.
4. If the actuator mechanism doesn't move even though the electrical connection has been verified or moves erratically the turbocharger is defective and must be replaced as an entire assembly.