Engine Code AHU

Special Tools, Testers And Auxiliary Items:
- VAG1397A turbocharger tester

Checking Conditions:
- No malfunctions stored in Diagnostic Trouble Code (DTC) memory
- Perform output Diagnostic Test Mode (DTM)
- No leaks from intake and exhaust systems
- Wastegate control line is not blocked, loose or leaking
- No engine or fuel injection mechanical malfunctions, e.g. start of injection, fuel injectors and compression pressure
- Engine oil temperature 80°C (176°F) minimum
- Measure boost pressure under full load, while driving on open road.
- Duration of test per measurement: 10 seconds maximum




Procedure:
- Disconnect harness connector -2- from wastegate bypass regulator valve -1- (-N75-).
Reconnect -N75- after check.





- Disconnect connecting hose running between intake manifold and Diesel Direct Fuel Injection (DFI) Engine Control Module (ECM) -J248-.
- Using tee, connect VAG1397A turbocharger tester and select measuring range II.

NOTES:
- To operate the VAG1397A turbocharger tester see manufacturers operating instructions.
- Make sure that all of the hoses are connected so there is no possibility of leakage.
- If boost is being measured while driving, a second person must be used to read and operate turbocharger tester.
- Make sure that the pressure hose is not trapped between the hood and the body.

- Measure boost pressure at wide open throttle.
While driving on an open road:
- In 2nd gear (manual) or with transmission range selector lever in position 1 (automatic).
- Under acceleration at wide open throttle while watching the tachometer.

NOTE: Do not apply the brakes while taking boost measurements (unless of course it becomes necessary). The engine control module responds to braking by reducing fuel quantity; which can lead to incorrect boost measurements.

- Press "M" button (memory) on VAG 1397A turbocharger tester when engine speed falls between 3500 and 4000 RPM, then read out boost values.

Specification: 0.50 to 0.65 bar (relative pressure).

If specified boost pressure NOT obtained:
- Check wastegate bypass regulator valve and replace if necessary.
- Repeat boost pressure check.

If specified boost pressure still NOT obtained:
- Replace turbocharger.

If boost pressure is exceeded:
- Check wastegate bypass regulator valve -N75-.
Flow between turbocharger and valve to wastegate should not be blocked when connector is disconnected.
- Make sure that turbocharger wastegate valve is securely mounted on turbocharger.
- Check wastegate and operating rod, replace if necessary.
- Check wastegate shaft mounting in turbocharger for ease of movement. If corroded together; replace turbocharger.