KC-478

1/31/22, 6:25 PM
Article
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Variable Geometry Turbocharger ( VGT
) Function Test ( 2551-08-03-02 ), OBD13 Model
Year ( MY ) 2014 And Newer
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Internal Content
Overview
The VGT Function Test has been improved to provide an accurate
graphical representation of turbo position during a sweep test.
Changes that have been made include:
2551-08-03-02 Variable Geometry Turbocharger Function test is
replacing the sector gear gauge tool as the primary method of
VGT diagnosis with more accuracy and less discrepancy.
VGT actuator motor effort has been removed from the
operation because it was resulting in misdiagnosis of the
turbocharger.
A plot of Variable Geometry Turbocharger position (black) and
error / status codes from Variable Geometry Turbocharger ( VGT
) / Smart Remote Actuator ( SRA ) (blue) has been added to the
operation for diagnosis.
Test Information
When performing the test:
Use the Step Test under option A for analysis. The step test is a
sweep of the VGT mechanism from open-close-open that takes
approximately 10 seconds. The graph must be manually
evaluated to determine a pass on the Step Test. Do not rely on
the green check mark status to determine a pass. The following
linked videos use a cutaway to illustrate what is happening
during the Step Test:
Actuator view End view Side view
; Live UI
https://volvo-trkna-prod1.pegacloud.net/prweb/PRAuth/app/VolvoKM_/iNPUIKpeinqPJi2G0hH930k43USdE1gb*/!TABTHREAD5?pyActivity=%40basec…
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Do not use the Full Stroke Test for VGT analysis as it is currently
under revision.
The Step Test can be repeated multiple times and at any
temperature that there is believed to be a problem.
See the image below for more information:
Interpreting Results:
Example 1 – Normal function turbocharger
Actuator closes to 0 - 5% during the step test AND
Status code from the VGT / SRA equals 0 or 7
No further troubleshooting is required, no component
replacement is required.
; Live UI
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Example 2 – Turbocharger actuator is unable to close to 0 - 5%
Symptom: VGT Actuator is unable to close to 0 - 5% during the
step test OR
Status code from the VGT / SRA changes from 7 - Test
Mode to 3 - Slow or Unable to Close
Result: Requires further troubleshooting to determine if the
actuator or the turbocharger is the defective component.
Dismount the actuator from the turbocharger and repeat the
Step Test with the actuator free. If the test again fails replace
only the actuator. If the actuator test passes, replace the
complete turbocharger.
; Live UI
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Example 3 – Turbocharger actuator is unable to close to 0 - 5%
Symptom: Turbo actuator is unable to close to 0 - 5% during the
Step Test.
Note: In this example, the status code from the VGT / SRA
does not change from 7 - Test Mode
Result: Requires further troubleshooting to determine if the
actuator or the turbocharger is the defective component.
Dismount the actuator from the turbocharger and repeat the
Step Test with the actuator free. If the test again fails replace
only the actuator. If the actuator test passes, replace the
complete turbocharger.
Note: This is a problem that will typically cause parked
regeneration failure.
; Live UI
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