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Air Induction Systems: Turbocharger

NOTE: VAS 5051 scan tool with VAG 5051/1 adapter cable and VAG 1598/31 test box or VAG 1551 with 1551/3A adapter cable are necessary to diagnose faulty turbocharger. Follow test equipment manufacturer's instructions for scan tool operation. The following tests are written specifically for turbocharger test VAG 1397A. A generic turbocharger test may not be capable of performing all necessary test functions.
NOTE: Before beginning testing procedure, drive vehicle quickly for at least 2 miles without stopping. To avoid an accident, a second ride along mechanic should participate in testing of turbocharger.
  1. Check all turbocharger hose and pipe connections for disconnected parts, leaks, torn or broken hoses. Connect VAS 5051 or equivalent scan tool to DLC. DLC is located behind cover under left side of steering column. See COMPONENT LOCATIONS  . Start engine. Using scan tool, initiate output Diagnostic Test Mode (DTM). See FUNCTION 03 - OUTPUT DIAGNOSTIC TEST MODE under SELF-DIAGNOSTIC SYSTEM in appropriate SELF-DIAGNOSTICS article. Scan tool should perform output DTM. If all actuators operate as specified, go to next step. If all actuators do not operate as specified, repair as necessary.
    2. NOTE: Charge pressure (turbo boost) level is measured with turbocharger tester VAG 1327A. VAS 5051 or VAG 1551 scan tool is used to verify that charge pressure is being received by ECM.
  2. Working in engine compartment, connect turbocharger tester VAG 1397A to intake manifold connection. See Fig 1 . Route measuring hose under rear edge of hood and into passenger compartment.
  3. Turn turbocharger tester on. Switch range selector to position "1" (absolute pressure). While engine is idling, on scan tool observe Measured Value Block DISPLAY GROUP 115.
  4. Test drive vehicle, accelerating at full throttle from 2000 RPM. At about 2500 RPM simultaneously press PRINT button on VAS 5051 or VAG 1551 scan tool and recall button "M" on turbocharger tester. Specified value on turbocharger tester should be 1.7-1.8 bar. Specified value in display group 115 display zone 4 on scan tool should be 1700-1800 m/bar. If displayed value is below specification, go to next step. If displayed value is above specification, go to step  6 . If displayed value is as specified, go to step  8 .
  5. If charge pressure is below specified value perform following tests:
    6. NOTE: If charge pressure is too high, fuel supply is interrupted in order to protect engine. This may result in engine misfire at high engine speeds.
  6. If charge pressure is above specified value perform following tests:
    • Vacuum unit for WBR valve faulty. See TURBOCHARGER in REMOVAL & INSTALLATION article.
    • Hose connection to vacuum unit for charge pressure limiter leaks. Go to step  7 .
    • When WBR valve sticks in closed position. See TURBOCHARGER in REMOVAL & INSTALLATION article.
  7. Check all hose and pipe connections. See appropriate diagram in VACUUM DIAGRAMS article, to aid in identifying turbocharger systems hoses and connections. If problem is found, repair as necessary. After repair, go to next step.
  8. Using scan tool, clear DTCs and generate a ECM readiness code. See FUNCTION 05 - CLEARING DIAGNOSTIC TROUBLE CODES and READINESS CODE under SELF-DIAGNOSTIC SYSTEM in appropriate SELF-DIAGNOSTICS article. Test drive vehicle. Using scan tool, retrieve DTCs. If DTC does not reset, testing is complete.
Fig 1: Connecting Turbocharger Tester
G00073541Courtesy of AUDI OF AMERICA, INC.
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