Engine coolant temperature sensor, checking

If the engine coolant temperature display in the instrument cluster is faulty, check whether the signal reaches the instrument cluster.

• Connect VAG 1551 or VAG 1552 scan tool. See VAG 1551, VAG 1552 SCAN TOOL (ST), CONNECTING AND SELECTING FUNCTIONS .
• Read measuring value block. See READ MEASURING VALUE BLOCK (SCAN TOOL FUNCTION 08) .
• Select channel number 003.

  If the coolant temperature is shown in the display of the scan tool, the instrument cluster is faulty and must be replaced.

  If also the scan tool does not show the coolant temperature in the display, check the multi-pin connector at the instrument cluster.

• Remove instrument cluster. See INSTRUMENT CLUSTER, REMOVING AND INSTALLING  .
• Connect VAG 1598 test box with VAG 1598/4 adapter to yellow 26-pin connector.
• With Fluke 83 multimeter, measure resistance between socket 19 and socket 12 (ground).

  Specified values:

  • Engine coolant temp. 90 °C (194 °F): approx. 110 Ohm
  • Engine coolant temp. 120 °C (248 °F): approx. 50 Ohm
• If you do not get these readings, check wiring to engine coolant temperature sensor.

  See appropriate System Wiring Diagram article.

• If the wiring is OK, replace engine coolant temperature sensor.