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 Fuel Temperature 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 Fuel Temperature 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 Fuel Temperature Sensor (3 Of 3)

  

If an implausible value appears in display field 1, or a substitute value of -5.4 C is displayed, check fuel temperature sensor and sensor and wiring:

• Press --> button.
• Press buttons -0- and -6- to select "End Output" function 06.
• Press -Q- button to confirm input.
• Switch ignition off.
• Disconnect fuel temperature sensor harness connector (connection to Diesel injection pump metering control).
  Fig 4: Identifying Fuel Temperature Sensor Connector Terminals

  

• Measure sensor resistance at terminals 4 and 7. See Fig 4 .
• Measure resistance across sensor terminals 4 and 7.
  • Specifications: refer to diagram
  • 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: Fuel Temperature Sensor Resistance Values Graph

  

If resistance is outside the specified range:

• Replace diesel fuel injection pump, see DIESEL INJECTION PUMP, REMOVING AND INSTALLING  .
• 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 7 and test box socket 63
  • Terminal 4 and test box socket 33
  • Wire resistance: max. 1.5 ohms (ohm)
  Fig 7: Identifying Fuel Temperature Sensor Harness Connector Terminals

  
• Check wiring for short circuit between 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) .