With Manufacturer's Scan Tool

Engine Coolant Temperature (ECT) sensor, checking

Special tools and equipment
- VAG1551 or VAG1552 Scan Tool (ST) with VAG1551/3 adapter cable
- VAG1598/22 test box
- Multimeter US1119 (Fluke 83 or equivalent)
- VW1594 connector test kit
- Wiring diagram

Checking requirements
- Engine cold

NOTE: The Engine Control Module (ECM) will use the intake air temperature as a replacement value for an engine start (start temperature replacement value) as soon as there is a Diagnostic Trouble Code (DTC) stored in DTC memory for the Engine Coolant Temperature (ECT) sensor -G62-. The temperature then rises according to a program stored in the ECM. When the engine has reached normal operating temperature a fixed replacement value will be displayed. This fixed value is also dependent upon the intake air temperature.

Checking
- Connect VAG1551 or VAG1552 scan tool and press buttons -0- and -1- to insert "Engine Electronics" address word 01 (with ignition switched; engine not running.

Indicated on display

Rapid data transfer HELP
Select function XX

- Press buttons -0- and -8- to select "Read Measuring Value Block" function 08, and press -Q- button to confirm input.

Indicated on display

Read Measuring Value Block HELP
Input display group number XXX

- Press buttons -0-, -0- and -4- to input display group number 4 (004), and press -Q- button to confirm input.

Indicated on display (1-4 = display fields)

Read Measuring Value Block 4 ->
1234

- Compare display with specified value for engine coolant temperature sensor (display field 3):

Display Group 4:

- Start engine and let run at idle.

Temperature value must increase evenly.

If displayed values are NOT OK:
- Press -> button.
- Press buttons -0- and -6- to select "End Output" function 06, and press -Q- button to confirm input.
- Switch ignition off.
- Replace Engine Coolant Temperature (ECT) sensor -G62-.

NOTE:
- Temperature is displayed in increments of 1.5 °C.
- If malfunctions occur within certain temperature ranges while the engine is running, and the temperature values do not increase without interruption, the temperature signal is intermittently interrupted and the sensor must be replaced.

Evaluation of display group 4, display field 3




Continuation of check when display reads approx. - 46 °C:






- Disconnect 4-pin connector -1- from Engine Coolant Temperature ECT sensor -2-.
- Bridge harness connector terminals 1 and 3 using adapter cables from VW1594 connector test kit.

When display is approx. 141°C:
- Press -> button.
- Press buttons -0- and -6- to select "End Output" function 06, and press -Q- button to confirm input.
- Switch ignition off.
- Replace Engine Coolant Temperature (ECT) sensor -G62-.

When display is approx. -46°C:
- Press -> button.
- Press buttons -0- and -6- to select "End Output" function 06, and press -Q- button to confirm input.
- Switch ignition off.
- Check wiring using appropriate wiring diagram.

Continuation of check when display reads approx. 141°C:






- Disconnect 4-pin connector -1- from Engine Coolant Temperature ECT sensor -2-.

When display is approx. -46°C:
- Press -> button.
- Press buttons -0- and -6- to select "End Output" function 06, and press -Q- button to confirm input.
- Switch ignition off.
- Replace Engine Coolant Temperature (ECT) sensor -G62-.

When display is approx. 141°C:

- Press -> button.
- Press buttons -0- and -6- to select "End Output" function 06, and press -Q- button to confirm input.
- Switch ignition off.
- Check wiring using appropriate wiring diagram.

Wiring, checking






- Connect VAG1598/22 test box to ECM harness connector.




- Disconnect 4-pin connector -1- from Engine Coolant Temperature (ECT) sensor -2-.

- Check wire between test box socket 67 and 4 pin connector terminal 3 for open circuit using wiring diagram.
Specified value: max. 1.5 Ohms

- Check wire between test box socket 53 and 4 pin connector terminal 1 for open circuit using wiring diagram.
Specified value: max. 1.5 Ohms

- Check wiring for short circuit between ECM/test box and 4-pin harness connector terminal 1 using wiring diagram.
Connector terminal 1 to vehicle Ground
Connector terminal 1 to ECM/test box socket 67
Specified value: Infinity Ohms

- Check wiring between ECM and 4-pin harness connector terminals 1 and 3 for short circuit to battery B+.
Specified value: Infinity Ohms

If wiring is OK:






- Check ECT sensor resistance across terminal 1 (signal) and terminal 3 (Ground).






The graph is divided into two temperature ranges:
Range A: 0-50°C (32-122°F)
Range B: 50-105°C (122-221°F)

Examples:
30°C (86°F) is in range A and corresponds to a resistance of 1.5-2.0 k Ohms
80°C (176°F) is in range Band corresponds to a resistance of 275- 375 Ohms

If resistance is NOT OK:
- Replace Engine Coolant Temperature (ECT) sensor -G62-.
- Check readiness code. If Diagnostic Trouble Code (DTC) memory has been erased, or ECM was disconnected, generate new readiness code. Monitors, Trips, Drive Cycles and Readiness Codes

If the wiring is OK and the resistance measurement values are OK.:
- Replace Motronic ECM -J220-. Service and Repair