With Manufacturer's Scan Tool
Engine Coolant Temperature (ECT) Sensors -G62- and -G2-, Checking
NOTE: The Motronic Engine Control Module (ECM) -J220- will use a replacement value for an engine start (start temperature replacement value) as soon as there is a Diagnostic Trouble Code (DTC) stored in the DTC memory, which affects the Engine Coolant Temperature (ECT) sensor -G62-. The temperature then rises according to a model stored in the control module. When the engine has reached normal working temperature a fixed replacement value will be displayed after a certain period.
Special tools, workshop equipment, testers, measuring instruments and auxiliary items required
- VAG 1551 Scan tool (or VAG 1552) with VAG 1551/3 adapter cable
NOTE: All functions which could previously be performed with VAG 1551/1552 can also be performed with the VAS 5051.
- VAG 1526 Hand multimeter or VAG 1715 multimeter
- VAG 1594 Adapter set
- VAG 1598/31 Test box
- Electrical Wiring Diagrams
Test prerequisites
- Selector lever must be in position "P" or "N" on vehicles with an automatic transmission.
- Engine must be cold.
Test sequence
NOTE: Only gold plated terminals may be used when servicing the sensor connector terminals.
- Connect VAG 1551 Scan tool (or VAG 1552). Then switch ignition on and select Motronic Engine Control Module (ECM) -J220- with the "Address word" 01. ((VAG 1551 and Motronic Engine Control Module (ECM) -J220-, connecting and selecting).
[1][2][3]Connecting VAG 1551 Scan Tool
Indicated on display:
Rapid data transfer HELP
Select function XX
- Press buttons -0- and -8- for function "Read measured value (data) block" and confirm entry with -Q- button.
Indicated on display:
Read measured value block
Input display group number XXX
- Press buttons -0-, -0- and -4- for "Display group number 4" and confirm entry with -Q- button.
Indicated on display: (1 to 4 = display zones)
Read measured value block 4 ->
1 2 3 4
- Read coolant temperature value in display zone 3.
Specification: approx. coolant temperature
If the specification is not obtained:
- Check according to the following table:
Display 1) Cause
Approx. - 42.0 degrees C Open circuit or short to positive
Approx. 136.0 degrees C Short to ground (GND)
1) If a temperature is displayed which deviates greatly from the ambient temperature of the sensor, check sensor wiring for transfer resistance.
If the specification is obtained:
- Start engine and run at idle speed. The temperature value must increase uniformly
NOTE: If irregular engine running occurs in certain temperature ranges and the temperature figure does not increase without interruption, the temperature signal is temporarily interrupted and the sensor must be replaced.
- Press the -> button.
- Press buttons -0- and -6- for function "End output" and confirm entry with the -Q- button.
- Switch off ignition.
If the display does not indicate as described:
- Replace Engine Coolant Temperature (ECT) sensor -G62- with Engine Coolant Temperature (ECT) sensor -G2-, item 14.
- Check DTC memory, repair malfunctions if necessary and then erase DTC memory.
Reading Diagnostic Trouble Codes
- Read readiness code. If the DTC memory has been erased or the Motronic Engine Control Module (ECM) -J220- was disconnected from battery positive (B+), the readiness code must be generated again.
Monitors, Trips, Drive Cycles and Readiness Codes
Monitors, Trips, Drive Cycles and Readiness Codes
Continuation of check when display reads approx. -42.0 degrees C:
- Pull 4-pin connector -arrow-off Engine Coolant Temperature (ECT) sensor -G62- with Engine Coolant Temperature (ECT) sensor -G2-.
- Jumper connector terminals 3 and 4 using adapter cables from VAG 1594 and observe display.
If display jumps to approx. 136.0 degrees C:
- Press the -> button.
- Press buttons -0- and -6- for function "End output" and confirm entry with the -Q- button.
- Switch off ignition.
- Replace Engine Coolant Temperature (ECT) sensor -G62- with Engine Coolant Temperature (ECT) sensor -G2-, item 14.
- Check DTC memory, repair malfunctions if necessary and then erase DTC memory.
Reading Diagnostic Trouble Codes
- Read readiness code. If the DTC memory has been erased or the Motronic Engine Control Module (ECM) -J220- was disconnected from battery positive (B+), the readiness code must be generated again.
Monitors, Trips, Drive Cycles and Readiness Codes
Monitors, Trips, Drive Cycles and Readiness Codes
If display remains at approx. -42.0 degrees C:
- Press the -> button.
- Press buttons -0- and -6- for function "End output" and confirm entry with the -Q- button.
- Switch off ignition.
- Check wiring referring to Electrical Wiring Diagrams.
Continuation of check when display reads approx. 136.0 degrees C:
- Pull 4-pin connector -arrow-off Engine Coolant Temperature (ECT) sensor -G62- with Engine Coolant Temperature (ECT) sensor -G2-.
If display jumps to approx. -42.0 degrees C:
- Press the -> button.
- Press buttons -0- and -6- for function "End output" and confirm entry with the -Q- button.
- Switch off ignition.
- Replace Engine Coolant Temperature (ECT) sensor -G62- with Engine Coolant Temperature (ECT) sensor -G2-, item 14.
- Check DTC memory, repair malfunctions if necessary and then erase DTC memory.
Reading Diagnostic Trouble Codes
- Read readiness code. If the DTC memory has been erased or the Motronic Engine Control Module (ECM) -J220- was disconnected from battery positive (B+), the readiness code must be generated again.
Monitors, Trips, Drive Cycles and Readiness Codes
Monitors, Trips, Drive Cycles and Readiness Codes
If display remains at approx. 136.0 degrees C:
- Press the -> button.
- Press buttons -0- and -6- for function "End output" and confirm entry with the -Q- button.
- Switch off ignition.
- Check wiring referring to Electrical Wiring Diagrams.
Checking wiring
- Remove wiper arms and cowl panel:
- Connect VAG 1598/31 test box to control module wiring harness. The Motronic Engine Control Module (ECM) -J220- remains disconnected.
- Check wiring for open circuit between test box and 4-pin connector referring to Electrical Wiring Diagrams.
Terminal 3 and socket 93
Terminal 4 and socket 108
Wire resistance: max. 1.5 ohms
- Additionally check wiring for short to one another, to vehicle ground (GND) and to battery positive.
Specification: infinity ohms
If no wiring malfunction is detected:
- Perform resistance measurement on Engine Coolant Temperature (ECT) sensor -G62- terminal C (signal) and D (ground).
Scale A shows resistance values for temperature range 0 to 50 degrees C and scale B the values for temperature range 50 to 100 degrees C.
Examples:
- 30 degrees C is in range A and corresponds to a resistance of 1.5 to 2.0 k ohms
- 80 degrees C is in range B and corresponds to a resistance of 275 to 375 ohms
If the specification is not obtained:
- Replace Engine Coolant Temperature (ECT) sensor -G62- with Engine Coolant Temperature (ECT) sensor -G2-, item 14.
- Check DTC memory, repair malfunctions if necessary and then erase DTC memory.
Reading Diagnostic Trouble Codes
- Read readiness code. If the DTC memory has been erased or the Motronic Engine Control Module (ECM) -J220- was disconnected from battery positive (B+), the readiness code must be generated again.
Monitors, Trips, Drive Cycles and Readiness Codes
Monitors, Trips, Drive Cycles and Readiness Codes
If there is no Diagnostic Trouble Code (DTC) in the wiring and the resistance measurement values are OK.:
- Replace Motronic Engine Control Module (ECM) -J220-.
- Check DTC memory, repair malfunctions if necessary and then erase DTC memory.
Reading Diagnostic Trouble Codes
- Erase learned values and adapt Motronic Engine Control Module (ECM) -J220- again.
- Read readiness code. If the DTC memory has been erased or the Motronic Engine Control Module (ECM) -J220- was disconnected from battery positive (B+), the readiness code must be generated again.
Monitors, Trips, Drive Cycles and Readiness Codes
Monitors, Trips, Drive Cycles and Readiness Codes