Test sequence

• Connect Scan Tool VAG 1551 ((VAG 1552) and select engine electronics control unit. Run engine at idle speed and press buttons -0- and -1- to select "Engine electronics" address word 01. (Connecting Scan Tool and selecting engine electronics control unit; see VAG 1551 SCAN TOOL, CONNECTING .)

Indicated on display:

• Press buttons -0- and -8- for the function "Read measured value block" and confirm entry with -Q- button.

Indicated on display:

• Press buttons -0-, -1- and -0- for "Display group number 10" and confirm entry with -Q- button.
• Observe display in display field 1.
• Specification: 230 to 370 mg/H
  Fig 3: Scan Tool Display - Checking Mass Air Flow (MAF) Sensor -G70 (3 Of 5)

  Courtesy of VOLKSWAGEN OF AMERICA, INC.

If the specification is not obtained:

• Check exhaust gas recirculation:

  See EXHAUST GAS RECIRCULATION, CHECKING

If the specification is obtained:

• Road test vehicle with a 2nd technician to observe display.

Observe valid safety precautions when road testing, see SAFETY PRECAUTIONS .

• Accelerate vehicle in 3rd gear (vehicles with manual transmission) or 2nd gear (vehicles with automatic transmission) from about 1500 rpm using wide open throttle.
• Press PRINT button on VAG 1551 at approx. 3000 rpm. The accelerator pedal must be fully depressed at this moment in time.
• Specification in display field 4: 100% (accelerator pedal position/throttle)
  Fig 4: Scan Tool Display - Checking Mass Air Flow (MAF) Sensor -G70 (4 Of 5)

  Courtesy of VOLKSWAGEN OF AMERICA, INC.

If the specification is not obtained:

• Repeat test and accelerate vehicle at wide open throttle.
• Specification in display field 1: above 800 mg/H (mass air flow drawn in).
  Fig 5: Scan Tool Display - Checking Mass Air Flow (MAF) Sensor -G70 (5 Of 5)

  Courtesy of VOLKSWAGEN OF AMERICA, INC.

If the specification is not obtained:

• Press the --> button.
• Press buttons -0- and -6- to select "End output" function 06 and confirm entry with the -Q- button.
• Switch off ignition.
• Replace MAF sensor.
• Check DTC memory and, if necessary, repair any malfunctions and then erase; see DIAGNOSTIC TROUBLE CODE (DTC) MEMORY, CHECKING AND ERASING .
• Read readiness code, see READING READINESS CODE . If the DTC memory has been erased or the Diesel Direct Fuel Injection Engine Control Module -J248- was disconnected from permanent battery positive (B+), the readiness code must be generated again; see READINESS CODE, SETTING .

If a constant 550 mg/H (predetermined replacement value) is displayed in display field 1.

• press --> the button.
• Press buttons -0- and -6- for the function "End output" and confirm entry with the -Q- button.
• Switch off ignition.
• Pull 5 -pin connector off MAF sensor -arrow-.
Fig 6: Pulling Pin Connector Off MAF Sensor
Courtesy of VOLKSWAGEN OF AMERICA, INC.
• Switch on ignition.
• Measure MAF sensor voltage supply between following connector contacts:
  Fig 7: Identifying MAF Sensor Harness Connector Terminals

  Courtesy of VOLKSWAGEN OF AMERICA, INC.
  MAF SENSOR VOLTAGE CHECK
  
  

  Terminal on -G70	Specification
  2 + Ground	App. battery voltage
  2 + 3	App. battery voltage
  4 + Ground	Approx. 5 V
  4 + 3	Approx. 5 V

If the specifications are not obtained:

• Switch off ignition.
• Remove wiper arms and plenum cover:

  See Plenum Cover Emoval & Installation

• Connect test box VAG 1598/31 to control module wiring harness.
Fig 8: Connecting Test Box VAG 1598/31 To Control Module Wiring Harness
Courtesy of VOLKSWAGEN OF AMERICA, INC.
• Check wiring between test box and connector for open circuit using wiring diagram.

  Terminal 2+ socket 1 and 2

  Terminal 3+ socket 49

  Terminal 4+ socket 30

  Terminal 5+ socket 68

  Wire resistance: max. 1.5 Ω

Fig 9: Identifying MAF Sensor Harness Connector Terminals
Courtesy of VOLKSWAGEN OF AMERICA, INC.
• Check wires for short to one another, to vehicle Ground and to battery positive (B+).

  Specification: INFINITY Ω

If no malfunction is detected in the wiring:

• Replace Diesel Direct Fuel Injection (DFI) Engine Control Module (ECM) -J248-, see DIESEL DIRECT FUEL INJECTION (DFI) ENGINE CONTROL MODULE .