Engine - Coolant Temperature Sensor/Switch: Testing and Inspection
Engine Coolant Temperature (ECT) sensor, checking
Required special tools and test equipment
- VAG 1551 or VAG 1552 Scan Tool (ST) with VAG 1551/3 adapter cable
- VAG 1598/22 test box
- Multimeter US 1119 (Fluke 83 or equivalent)
- VW 1594 connector test kit
- Wiring diagram
Test requirements
- Engine cold
Checking
- Connect VAG 1551 or VAG 1552 scan tool and press buttons -0- and -1- to insert "Engine Electronics" address word 01 (with ignition switched on).Refer to "Scan tool Testing/Scan Tool Connecting and Initial Checks/Connecting VAG 1551/VAG 1552 Scan Tool" Testing and Inspection
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 ->
1 2 3 4
- Compare display with specified value for engine coolant temperature sensor (display field 3):
Display Group 4:
Continuation
- Start engine and let run at idle.
- Temperature value must increase evenly.
If NOT:
- 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
Display Group 4:
Checking wiring
- Connect VAG 1598/22 test box to ECM harness connector.Refer to "Scan Tool Testing/Scan Tool Connecting and Initial Checks/Connecting VAG 1598/22 Test Box" Testing and Inspection
- Disconnect 4-pin connector from ECT sensor -G62-.
- Check wiring resistance for open circuit between ECM/test box and 4-pin ECT sensor connector.
- Connector terminal 1 to ECM/test box socket 53
- Connector terminal 3 to ECM/test box socket 67
- Specified value: max. 1.5 Ohms
- Check wiring for short circuit between ECM/test box and 4-pin harness connector according to wiring diagram.
- Connector terminal 1 to vehicle Ground
- Connector terminal 1 to ECM/test box socket 67
- Connector terminal 1 to terminal 3
- Connector terminal 3 to vehicle Ground
- Specified value: Infinity Ohms
- Check wiring between ECM and 4-pin harness connector for short circuit to battery B+.
- Connector terminal 1 to vehicle Ground
- Connector terminal 3 to vehicle Ground
- Specified value: 0 volts
If wiring is OK:
- Check ECT sensor resistance across terminal 1 (signal) and terminal 3 (ground).
- Check measured resistance value for appropriate temperature range using graph below, illustration (N24-0157).
- Range A: 0-50 ° C (32-122 ° F)
- Range B: 50-100 ° C (122-212 ° F)
Examples:
- At 30° C, ECT sensor resistance should be 1500-2000 Ohms
- At 80° C, ECT sensor resistance should be 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.
Refer to "Moniters, Trips and/or Drive Cycle (Readiness Codes)/Checking Readiness Code" Testing and Inspection
Refer to "Moniters, Trips and/or Drive Cycle (Readiness Codes)/Generating Readiness Code Testing and Inspection