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 - Fuel Temperature 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 - Fuel Temperature 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 - Fuel Temperature Sensor Test Sequence (3 Of 3)

  Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.
• Check fuel temperature value in display field 1.
  • The temperature value must be approx. ambient temperature.

  If a malfunction is present a constant -5.4 C will be displayed for the fuel temperature.

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

If display field 1 appears unrealistic or a substitute temperature of -5.4 °C is displayed, check fuel temperature sensor and wiring as follows:

• Disconnect 10-pin connector for fuel temperature sensor (connection to injection pump metering unit) -arrow-.
Fig 4: Disconnecting Pin Connector For Fuel Temperature Sensor (Connection To Injection Pump Metering Unit)
Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.
• Measure sensor resistance at connector terminals 4 + 7.
Fig 5: Identifying 10-Pin Connector Terminals
Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.

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

Examples:

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

If the specification is not obtained:

• Replace injection pump, see INJECTION PUMP, REMOVING AND INSTALLING .
• 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: Connecting 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 10-Pin Harness Connector Terminals

  Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.
  10-PIN HARNESS CONNECTOR TERMINAL SPECIFICATIONS (FUEL TEMPERATURE SENSOR)
  
  

  	Test box socket no.
  Terminal	Through MY 1999	From MY 2000
  4	76	103
  7	53	111

  • Wire resistance: max. 1.5 Ω

  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 .