Test sequence

• Connect VAG1551 or VAG1552 scan tool.
  1. 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 Engine Coolant Temperature (ECT) 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 Engine Coolant Temperature (ECT) 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 Engine Coolant Temperature (ECT) Sensor (3 Of 3)

  
• Check ECT value in display field 4.

Value must increase uniformly and without interruption

If an unreasonable value appears in display field 4, or the fuel temperature has been supplied as a substitute, check the ECT sensor and wiring connections to the sensor as follows:

• 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 from ECT sensor -1-.
  Fig 4: Disconnecting Harness Connector From ECT Sensor

  

• Measure resistance between sensor terminals 1 and 3. See Fig 4 .
  • Specifications: refer to diagram for resistance values
  • Scale A: for temperatures 0° -50°C (32°-122°F)
  • 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: ECT Sensor Resistance Values Graph

  

If resistance is outside the specified range:

• Replace engine coolant temperature sensor -G62-.
• 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 4 -pin connector and test box, using wiring diagram.
  Fig 7: Checking Wiring For Open Circuit Between ECT Sensor Pin Connector And Test Box

  
  • Terminal 1 + test box socket 33
  • Terminal 3 + test box socket 14
  • Wire resistance: 1.5 ohms (ohm) maximum
• Check wiring for short circuit between terminals at 4-pin connector.
  1. Specification: INFINITY ohm (no continuity)

If wiring is OK:

• Replace Diesel DFI ECM -J248-, see item  3 .
• Check and erase DTC memory, see ERASE DTC MEMORY (SCAN TOOL FUNCTION 05) .