Boost Pressure Control
Special tools, workshop equipment, test and measuring appliances and auxiliary items required:
- VAG 1390 Hand vacuum pump
- Fluke 83 Multimeter or equivalent
- VW 1594 Adaptor kit
- VAG 1598/22 Test Box
- VAG 1551/1552 Scan Tool using VAG 1551/3 Adaptor cable
- Wiring diagram
Checking requirements:
- No intake or exhaust system leaks.
- No malfunctions in engine and fuel injection system, e.g. start of injection, injectors and compression pressure.
- Engine oil temperature min. 80 °C minimum.
Test sequence:
Observe following if test and measuring instruments are required during a test drive:
- Test and measuring instruments must be secured to rear seat and operated by a 2nd person from this location.
WARNING! If test and measuring instruments are operated from the front passenger's seat and the vehicle is involved in an accident, there is the possibility that the person sitting in this seat could receive serious injuries from the test instruments if the airbag is triggered.
- Boost pressure is measured using the VAG 1551/1552 Scan Tool during a test drive.
- Connect VAG 1551/1552 Scan Tool
Refer to "On Board Diagnostic (OBD II), Connecting and Operating VAG 1551 Scan Tool". Testing and Inspection
- Engine must be running at idle.
- Press 0 and 1 buttons to select address word 01
"Engine electronics"
Display will appear as shown
Rapid data transfer HELP
Select function XX
- Press 0 and 8 buttons to select Function 08
"Read measuring value block"
- Press Q button to enter input
Display will appear as shown
Read measuring value block HELP
Input display group number XXX
- Press 0,1 and 1 buttons to select Display Group 11
- Press Q button to enter input
Display will appear as shown
Read measuring value block 11 ->
840 rpm 938 mbar 978 mbar 92 %
- Accelerate vehicle in 3rd gear (manual transmission) or with driving range 2 selected (automatic transmission) from about 1500 rpm using Wide Open Throttle.
- Press VAG 1551 PRINT button at approx. 3000 rpm.
Specification in-display zone 3: 1700 to 2300 mbar
Read measuring value block 11 ->
3090 rpm 1866 mbar 1917 mbar 62 %
If specification not obtained
- With vehicle stationary perform Output Diagnostic Test Mode to activate the Wastegate Bypass Regulator valve:
Refer to "On Board Diagnostic (OBD II), Output Diagnostic Test Mode (DTM)". Testing and Inspection
Display will appear as shown
Output Diagnostic Test Mode ->
Wastegate Bypass Regulator valve -N75
NOTES:
- The Wastegate Bypass Regulator valve must function and the Boost pressure control valve rod must move to and fro (at least 3 to 4 times, as long as there is vacuum in the reservoir).
- Due to rod location, movement can only be observed by using a mirror.
- Perform Output Diagnostic Test Mode
If rod moves and boost pressure specifications not obtained during test drive:
- Replace turbocharger.
If rod does not move because Wastegate Bypass Regulator valve not working:
- Check Wastegate Bypass Regulator valve N75.
- Check vacuum hoses.
If rod does not move but solenoid operates:
- Connect VAG 1390 hand vacuum pump to Wastegate Bypass Regulator valve and verify that rod moves freely.
If rod does not move easily:
- Replace turbocharger assembly
Wastegate Bypass Regulator valve N75, checking:
- Switch OFF ignition.
- Disconnect Wastegate Bypass Regulator valve.
- Measure resistance between valve terminals.
- Specification: 14 to 20 Ohms
If specification not obtained:
- Replace Wastegate Bypass Regulator valve N75
If specification obtained:
- Switch ON ignition.
- Measure supply voltage between valve connector terminal 1 and engine Ground.
- Specification: approx. battery voltage
If specification not obtained:
- Switch OFF ignition.
- Connect VAG 1598/22 Test Box to Engine Control Module wiring harness.
- Check wiring for open circuit between Test Box and harness connector using wiring diagram.
Terminal 1 + socket 28 + 2
Terminal 2 + socket 15
Internal resistance of wire: 1.5 Ohms maximum
- Also check wires for shorting to one another, to vehicle Ground and to Battery positive.
- Specification: Infinity Ohms
If wiring OK:
- Replace Diesel Direct Injection system Engine Control Module J248.
- Check DTC memory and if necessary create readiness code. If DTC memory has been erased, Readiness code must be created again.
efer to "On Board Diagnostic (OBD II), Readiness Code - Reading/Creating". Testing and Inspection