Test sequence

• Connect V.A.G 1551/1552 (Connecting scan tool and selecting engine electronics control module: see VAG 1551 SCAN TOOL, CONNECTING .)
• Run engine at idle speed and press buttons -0- and -1- to select "Engine electronics" address word 01.

  Indicated on display

  Fig 1: Scan Tool Display - Intake Air Temperature (IAT) Sensor Test Sequence (1 Of 3)

  Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.
• Press buttons -0- and -8- to select "Read measured value block" function 08 and confirm entry with -Q- button.

  Indicated on display

  Fig 2: Scan Tool Display - Intake Air Temperature (IAT) Sensor Test Sequence (2 Of 3)

  Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.
• Press buttons -0-, -0- and -7- to select "Display group number 7" and confirm entry with -Q- button.

  Indicated on display

  Fig 3: Scan Tool Display - Intake Air Temperature (IAT) Sensor Test Sequence (3 Of 3)

  Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.
• Check intake air temperature value in display field 3.
  • The temperature value must be approx. ambient temperature.

  If a malfunction is present, a constant 136.8 °C will be displayed for the intake air temperature.

• Press --> button
• Press buttons -0- and -6- to select "End output" function 06 and confirm entry with -Q- button.
• Switch ignition off.

If display in field 3 appears unrealistic or a substitute temperature of 136.8 °C is displayed, check IAT sensor and wiring as follows:

• Disconnect 4-pin connector from Manifold Absolute Pressure (MAP) Sensor -G71- with IAT Sensor -G72- (arrow).
Fig 4: Disconnecting Pin Connector From Manifold Absolute Pressure (MAP) Sensor With IAT Sensor
Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.
• Measure resistance between sensor terminals 1 + 2.
Fig 5: Identifying MAP/IAT Sensor Terminals
Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.

• Specification: correlate resistance measurement with chart
Fig 6: MAP/IAT Sensor Temperature Versus Resistance Graph
Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.

Examples:

• 30 °C corresponds to a resistance from 1500 to 2000 Ω
• 80 °C corresponds to a resistance from 275 to 375 Ω

If the specification is not obtained:

• Replace MAP sensor -G71- together with IAT sensor -G72-.
• 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 READINESS CODE, DISPLAYING .

If the DTC memory has been erased or the engine control module was disconnected from permanent battery positive (B+), the readiness code must be generated again: see READINESS CODE, SETTING .

If the specification is obtained:

• Remove wiper arms and plenum cover.

  See Plenum Cover Emoval & Installation

• Connect test box VAG 1598/22 (through my 1999) or VAG 1598/31 (from my 2000) to control module wiring harness.
Fig 7: Connect Test Box Vag 1598/22 Or Vag 1598/31 To Control Module Wiring Harness
Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.
• Check wiring between test box and connector for open circuit according to wiring diagram.
  Fig 8: Identifying MAP/IAT Sensor Harness Connector Terminals

  Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.
  MAP/IAT SENSOR HARNESS CONNECTOR TERMINAL SPECIFICATIONS
  
  

  	Test box socket no.
  Terminal	Through MY 1999	From MY 2000
  1	25	52
  2	13	73

  • Wire resistance: max. 1.5 Ω
• Additionally check wires for short to one another, to vehicle Ground and to battery positive (B+).
  • Specification: INFINITY Ω

If wiring and the resistance measurement values are OK:

• Replace engine control module, see DIESEL DIRECT FUEL INJECTION (DFI) ENGINE CONTROL MODULE (ECM) -J248-, REPLACING .