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Home >> Volkswagen >> 2001 >> Passat GLX Wagon (3B6) V6-2.8L (ATQ) >> Repair and Diagnosis >> Powertrain Management >> Computers and Control Systems >> Sensors and Switches - Computers and Control Systems >> Coolant Temperature Sensor/Switch (For Computer) >> Testing and Inspection >> With Manufacturer's Scan Tool

With Manufacturer's Scan Tool



Engine Coolant Temperature (ECT) sensor, checking

Special tools and equipment

- V.A.G 1551 Scan Tool (or VAG 1552 mobile scan tool) with VAG 1551/3 cable
- VAG 1598/31 test box
- VAG 1526 multimeter or VAG 1715 multimeter
- VAG 1594 connector test kit
- Wiring diagram

Test condition

- Engine must be cold.

Test sequence

- Connect V.A.G 1551 scan tool (VAG 1552). Switch ignition on and select Engine Control Module (ECM) using address word 01. [1][2][3]Connecting VAG 1551 Scan Tool

Indicated on display

Rapid data transfer HELP
Select function XX

- Press buttons -0- and -8- to select "Read measuring value block" function 08. Press -Q- button to confirm input.

Indicated on display

Read Measuring Value Block HELP
Input display group number XX

- Press 0, 0 and 4 for function "display group number 4", and then press Q to exit from input mode.

Indicated on display (1 - 4 = display fields)

Read Measuring Value Block 4 ->
1 2 3 4

- Read coolant temperature value in display field 3.
Specification: approx. coolant temperature

If specified value is not obtained:

- Continue testing according to following table:

Indication1) Cause
approx. -48°C Break or short to B+
approx. 143°C Short circuit to Ground

1) If a temperature is indicated which differs greatly from ambient temperature of sensor, check sensor wires for contact resistance.

If the specified value is met:
- Start engine, and let it idle.

The temperature should climb uniformly

NOTE:
- The temperature climbs in increments of 1.0 °C.
- If the engine shows problems in certain temperature ranges and if the temperature does not climb uniformly, the temperature signal is intermittent and the sensor should be replaced.

- Press -> button.
- Press buttons -0- and -6- to select "End Output" function 06. Press -Q- button to confirm input.

Continuation of test if indication is approx. -48°C:

- Pull 4-way connector off Engine Coolant Temperature (ECT) sensor -G62-.
- Connect together terminals 3 + 4 of connector using auxiliary wires from VAG 1594, and observe what is indicated on display.

If indication jumps to approx. 143°C:
- Press -> button.
- Press buttons -0- and -6- to select "End data transfer" function 06. Press -Q- button to confirm input.
- Switch ignition off.
- Replace Engine Coolant Temperature (ECT) sensor -G62-.

If indication remains at approx. -48°C:
- Press -> button.
- Press buttons -0- and -6- to select "End data transfer" function 06. Press -Q- button to confirm input.
- Switch ignition off.
- Check wires (see wiring diagram)

Continuation of test if indication is approx. 143°C:

- Pull 4-way connector off Engine Coolant Temperature (ECT) sensor -G62-.

If indication jumps to approx. -48°C:
- Press -> button.
- Press buttons -0- and -6- to select "End data transfer" function 06. Press -Q- button to confirm input.
- Switch ignition off.
- Replace Engine Coolant Temperature (ECT) sensor -G62-.

If indication remains at approx. 143°C:
- Press -> button.
- Press buttons -0- and -6- to select "End data transfer" function 06. Press -Q- button to confirm input.
- Switch ignition off.
- Check wires (see wiring diagram)

Checking wires





- Connect VAG 1598/31 test box to control module wiring harness. Engine Control Module (ECM) is not connected.
- Pull 4-way connector off Engine Coolant Temperature (ECT) sensor -G62-.






- Check for breaks in wires between test box and 4-way connector (see wiring diagram).
Terminal 3 + socket 108
Terminal 4 + socket 93
Wire resistance: max. 1.5 Ohms

- Check wire between test box and terminal 3 of 4-way connector for short to terminal 4 wire and to vehicle ground (see wiring diagram).
Terminal 4 + socket 108
Terminal 4 + vehicle Ground (GND)
Expected value: infinity Ohms

- Also check both wires for shorts to battery B+.

If no malfunctions are found in wire:






- Measure resistance at Engine Coolant Temperature (ECT) sensor -G62-, terminals C (signal) and D (Ground (GND)).






Range A shows the resistance values for the temperature range from 0-50 °C, and range B shows the values for the temperature range from 50-100 °C.

Examples of how to read the diagram:
- 30 °C is in range A and corresponds to a resistance of 1.5-2.0 Kohms
- 80 °C is in range B and corresponds to a resistance of 275-375 Ohms

If specified value is not obtained:
- Replace Engine Coolant Temperature (ECT) sensor -G62-.

If no DTCs are found in the wires and the resistance values are in order:
- Replace Engine Control Module (ECM).

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