Audi Workshop Service and Repair Manuals

Notes:

• ◆ Fitting location of coolant temperature sender .

Test requirements:

• ● Engine cold

Test sequence

• ‒ Connect up vehicle diagnostic, testing and information system VAS 5051 or fault reader V.A.G 1551 and select engine electronics control unit with "Address word" 01 => Page 01-8.
  For this purpose, the engine must be running at idle speed

• ‒ Enter "08" to select the function "Reading measured value block" and confirm entry with Q key.

• ‒ Enter "004" for "display group number 004" and confirm entry with Q key.

• ‒ Check display in display zone 3.

If display zone 3 shows an implausible value:

• ‒ Disconnect connector on coolant temperature sender.

Coolant temperature sender with square plug:

• ‒ → Connect multimeter to contacts 1 and 3 of sender to measure resistance.

Coolant temperature sender with oval plug:

• ‒ → Connect multimeter to contacts 3 and 4 of sender to measure resistance.

All models:

Range A shows resistance values for temperature range 0...50 oC and range B the values for temperature range 50...100 oC.

→ Sample readings:

• ◆ 30 oC corresponds to a resistance of 1500...2000 ω
• ◆ 80 oC corresponds to a resistance of 275..375 ω

If specified value is not attained:

• ‒ Replace coolant temperature sender.

If specified value is attained:

• ‒ Connect the V.A.G 1598/31 test box to wiring harness leading to engine control unit; the engine control unit should not be connected => Page 24-22.

Coolant temperature sender with square plug:

• ‒ → Check for open circuit and short to positive or earth in the following wiring connections:

Coolant temperature sender with oval plug:

• ‒ → Check for open circuit and short to positive or earth in the following wiring connections:

All models:

• ‒ Test for short circuits between the two wires.
• ‒ Rectify any open/short circuit as necessary.

If no wiring fault is detected:

• ‒ Fit a new engine control unit => Page 24-26.