Test sequence

• Connect VAG1551 or VAG1552 scan tool, see VAG1551 SCAN TOOL (ST), CONNECTING .
• Start engine and let idle.
• Press buttons -0- and -1- to insert the "Engine Electronics" address word 01.

Indicated on display

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

• Press buttons -0- and -8- to select "Read Measuring Value Block" function 08.
• Press -Q- button to confirm input.

Indicated on display

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

• Press buttons -0-, -0- and -7- to input display group no. 7 (007).
• Press -Q- button to confirm input.
• Indicated on display
  Fig 3: Scan Tool Display - Checking Intake Air Temperature (IAT) Sensor (3 Of 3)

  

If an implausible value appears in display field 3, or a substitute value of 136.8°C is displayed, check intake air temperature sensor and sensor wiring:

• Press --> button.
• Press buttons -0- and -6- to select "End Output" function 06.
• Press -Q- button to confirm input.
• Switch ignition off.
• Disconnect harness connector -1- from intake air temperature sensor -2-.
  Fig 4: Disconnecting Harness Connector From Intake Air Temperature Sensor

  

• Measure resistance across sensor terminals.
  • Specifications: refer to diagram for resistance values
  • Scale A: for temperatures 0° -50°C (32° -122°F). See Fig 5 .
  • Scale B: for temperatures 50° -100°C (122°-212°F)

  Examples:

  • 30°C (86°F) corresponds to 1500-2000 ohms (ohm) resistance
  • 80°C (176°F) corresponds to 275-375ohms (ohm) resistance
  Fig 5: Intake Air Temperature Sensor Resistance Values Graph

  

If resistance is outside the specified range:

• Replace Intake Air Temperature (IAT) sensor -G72-.
• Display readiness code, see READINESS CODE, DISPLAYING .

If DTC memory was erased:

• Create readiness code again, see READINESS CODE, SETTING (UP TO M.Y. 1997) .

If resistance is OK:

• Connect VAG1598/18 test box to Diesel DFI ECM connector.
  Fig 6: Connecting VAG1598/18 Test Box To Diesel DFI ECM Connector

  
• Check wiring for open circuit between test box and harness connector, using wiring diagrams:
  • Terminal 1 and test box socket 64
  • Terminal 2 and test box socket 33
  • Wire resistance: max. 1.5 ohms (ohm)
• Check wiring for short circuit between connector terminals.
  Fig 7: Identifying Intake Air Temperature Sensor Harness Connector Terminals

  

Specification: INFINITY ohm (no continuity)

If wiring is OK:

• Replace Diesel DFI ECM -J248-, see item  3 .
• Display readiness code, see READINESS CODE, DISPLAYING .

If DTC memory was erased:

• Create readiness code again, see READINESS CODE, SETTING (UP TO M.Y. 1997) .