Boost Pressure Control

Special Tools, Testers And Auxiliary Items:
- VAG 1551/1552 Scan Tool with VAG 1551/3 adaptor cable
- VAG 1397 A Turbocharger tester
- VAG 1598/18 Test Box
- Fluke 83 multimeter (or equivalent)
- VW 1594 adaptor kit
- Wiring diagram

Test Sequence:
- Connect VAG 1551/1552 Scan Tool
- Start engine and let idle
- Press 0 and 1 buttons to select address word 01 "engine electronics"

NOTE: To check boost pressure control it is essential that boost pressure first be measured without the influence of pressure limiting (control). Check Turbocharger

- Measure boost pressure using VAG 1551 Scan Tool during a test drive

CAUTION: When "on the road" measurements are required for diagnosis, for obvious safety reasons, always use a second technician to take the instrument readings.

- Ensure that Wastegate Bypass Regulator valve N75 harness connector is connected
- Connect VAG 1551/1552 Scan Tool
- Start engine and let 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 XX

- Press 1 and 1 buttons to display group number 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 from about 1500 rpm using Wide Open Throttle
- Press PRINT button on VAG 1551 at about 3000 rpm
Display will appear as shown:

Read measuring value block 11
3090 rpm 1866 mbar 1917 mbar 62%

VAG 1551 Specified value: 1720 to 1950 mbar (display zone 3)

If measured boost pressure is too low:
- Check Wastegate Bypass Regulator valve

Wastegate Bypass Regulator Valve, Electrical Checks:
- Switch OFF ignition
- Disconnect Wastegate Bypass Regulator valve harness connector
- Switch Fluke 83 multimeter to resistance range





- Connect multimeter between valve terminals and measure resistance
Specification: 25 to 45 Ohms.

If specification not obtained:
- Replace Wastegate Bypass Regulator valve N75
- Display the readiness code

If DTC memory was erased:
- Create readiness code again

Wastegate Bypass Regulator Valve N75, Voltage Supply Checking:
- Switch OFF ignition
- Disconnect Wastegate Bypass Regulator valve harness connector
- Switch Fluke 83 multimeter to 20 Volt measurement range





- Connect Fluke 83 multimeter between terminal 1 and Ground using jumper wires from VW 1594 adaptor kit
- Switch ON ignition
Specification: approx battery voltage.

If specification not obtained:
- Check wiring connection to Wastegate Bypass Regulator valve N75
- Switch OFF Ignition





- Connect VAG 1598/18 Test Box to ECM harness connector





- Check wiring for open circuit between Test Box and connector using wiring diagram:
terminal 1 + socket 68
terminal 2 + socket 47
Wire resistance: max. 1.5 Ohms.

- Also check wires for shorting to one another
Specification: Infinite Ohms.

- Repair any open or short circuit as necessary.

If neither an open nor short circuit exists:
- Replace Diesel direct injection system ECM J248
- Display the readiness code

If DTC memory was erased:
- Create readiness code again