Engine Coolant Temperature (ECT) Sensor - Checking
24 07 09May 24, 2007
2010627, Supersedes Technical Bulletin Group 24 number 07-07 dated Mar. 9, 2007 due to addition of City Golf, City Jetta Models.
Engine Coolant Temperature (ECT) Sensor -G62- Checking
Condition
Vehicle Information
Technical Background
Not applicable.
Production Solution
Not applicable.
Service
Use the following when ECT or cooling system faults are present in fault memory.
Applies to vehicle and engine codes listed in the table.
Engine Coolant Temperature (ECT) Sensor, Checking
WARNING
The cooling system is under pressure. Danger of scalding when opening! Allow engine to cool before opening cooling system.
Do not use this procedure or replace Engine Coolant Temperature Sensor -G62- if no fault codes are stored or fault codes unrelated to coolant system are present. Check vehicle history, if Engine Coolant Temperature Sensor -G62- has already been replaced, it is not likely to be defective.
Before completing repair, see note below regarding fault code information and other possible causes.
Note:
If DTCs P1296, P2181, P0128 or P3081 are occurring without electrical faults (P0116-P0118) and replacement of Engine Coolant Temperature Sensor -G62- and its terminals repaired, check thermostat and cooling system for proper operation. Ensure fan control unit part no. is valid for vehicle, if equipped. Always see ETKA for the latest part(s) information.
Tip:
The Engine Control Module (ECM) will use a replacement temperature value for an engine start as soon as there is a 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 ECM. When the engine has reached normal working temperature a fixed replacement value will be displayed after a certain period. This fixed value is also dependent on intake air temperature.
Note:
Only gold-plated terminals must be used to repair the terminals in the wiring harness connector for the Engine Coolant Temperature (ECT) Sensor -G62-.
Special Tools and Equipment
See Required Parts and Tools
Checking Conditions
1. Fuses of Motronic Engine Control Module (ECM) -J220- must be valid. See ElsaWeb; Electrical Wiring Diagrams, Troubleshooting and Component Locations.
2. Parking brake must be engaged or daylight running lights will be switched ON.
3. For vehicles with automatic transmission, selector lever must be in Park position.
4. Ground connections between engine and chassis must be valid.
5. Engine must be cold (50°C (122°F) maximum).
6. Battery must be fully charged and in good condition.
Test Sequence
Note:
While following tests in this Technical Bulletin, always visually inspect terminals of electrical connectors for damage, corrosion and secure fit. Repair as necessary.
^ Connect VAS 5051/5052 diagnostic tool.
^ Switch ignition ON.
^ Select "Vehicle Self-Diagnosis".
^ Select vehicle system "01 - Engine electronics".
^ Select diagnosis function "011 - Measured values".
Input "4" on keypad to select "Display group 4" or "7" for "Display group 7" (as indicated in above table). See Service.
^ Confirm with "Q" button.
^ Read coolant temperature value in "Field 3" or "Field 4" (as indicated in above table). See Service.
Specification: approx. coolant temperature
If the specification is not obtained:
Perform check according to table shown.
1) If a temperature is displayed which deviates greatly from the ambient temperature of the sensor; -G62- sensor or its wiring have high resistance or a short to B+.
While observing the displayed temperature, gently wiggle ECT connector.
Tip:
Refer to component locations in ElsaWeb for location of ECT sensor -G62-.
If display fluctuates by more than 3°:
^ Replace ECT sensor. See ElsaWeb. If sensor was already replaced, repeat wiggle test.
If temperature still fluctuates more than 3°:
^ Replace wiring harness connector terminals.
Continue:
Start engine and run at idle speed. Observe temperature value for uniform consistent increase until 85° C (185°F) is attained.
The temperature rises in steps of 1.0°C.
Temperature may drop slightly as thermostat opens. This is normal.
If irregular engine running occurs in certain temperature ranges or the temperature figure changes erratically, the temperature signal is temporarily interrupted and the sensor must be replaced.
^ Select backward arrow on navigation bar.
^ Select diagnosis function "022 - End output".
Tip:
If temperature display rises uniformly and all specifications are normal. Proceed to "-G62- Resistance Measurement" (see below).
Continuation of Check When Display Approx. - 40°C (- 40°F)
^ Disconnect 4-pin connector from Engine Coolant Temperature (ECT) Sensor -G62- (arrow).
^ Connect VAS 5258 to 4 pin -G62- connector from vehicle engine harness. ECT sensor remains disconnected.
^ Bridge VAS 5258 test probes 3 + 4 using auxiliary cables from VAG 1594C and observe display.
If display jumps to approx. 140°C (284°F):
^ Select backward arrow on navigation bar.
^ Select diagnosis function "022 - End output".
^ Switch ignition OFF.
^ Replace Engine Coolant Temperature (ECT) sensor -G62-. See ElsaWeb.
^ Check DTC memory, if necessary, repair any malfunctions and then erase DTC memory.
^ Read readiness code. If DTC memory has been erased, readiness code must be generated again.
^ If display remains at approx. - 40°C (- 40°F):
^ Select backward arrow on navigation bar.
^ Select diagnosis function "022 - End output".
^ Switch ignition OFF.
^ Proceed to "Checking Wiring".
Continuation of Check When Display Approx. 140°C (284°F)
Disconnect 4-pin connector from Engine Coolant Temperature (ECT) Sensor -G62- (arrow).
If display jumps to approx. - 40°C (- 40°F):
^ Select backward arrow on navigation bar.
^ Select diagnosis function "022 - End output".
^ Switch ignition OFF.
^ Replace Engine Coolant Temperature (ECT) Sensor -G62-. See ElsaWeb.
^ Check DTC memory, if necessary, repair any malfunctions and then erase DTC memory.
^ Read readiness code. If DTC memory has been erased, readiness code must be generated again.
If display remains at approx. 140°C (284°F):
^ Select backward arrow on navigation bar.
^ Select diagnosis function "022 - End output".
^ Switch ignition OFF.
^ Proceed to "Checking Wiring".
Checking Wiring
Tip:
Refer to applicable Repair Manual section for instructions regarding engine or diesel control module access.
^ Connect correct VAG 1598 test box, (as indicated in above table). See Service, to control module wiring harness. Engine control module is not connected by this action.
^ Disconnect 4-pin connector from Engine Coolant Temperature (ECT) Sensor -G62- (arrow).
^ Connect VAS 5258 connector to 4 pin -G62- connector from vehicle engine harness. ECT sensor remains disconnected.
Note:
For all engines except TDI and Passat.
^ Check wire for open circuit between VAG 1598 test box and VAS 5258 according to wiring diagram.
VAS 5258 probe 3 + Socket 93
VAS 5258 probe 4 + Socket 108
Wire resistance: max. 1.5 ohms
Note:
For Passat with engine codes: ATW, AUG, AWM, ATQ.
^ Check wires between VAG 1598 test box and VAS5258 for open circuit according to wiring diagram.
VAS 5258 probe 3 + Socket 108
VAS 5258 probe 4 + Socket 93
Wire resistance: max. 1.5 ohms
Note:
For TDI with engine code ALH.
^ Check wires between VAG 1598 test box and VAS 5258 for open circuit using wiring diagram.
VAS 5258 probe 3 + Socket 112
VAS 5258 probe 4 + Socket 104
Wire resistance: max. 1.5 ohms
Note:
For TDI-PD vehicle with engine codes BEW, BHW.
^ Connect adapter cable (VAG 1598/39-1 and 1598/39-2) to test box (VAG 1598/42).
^ Check wires between VAG 1598 test box and VAS 5258 for open circuit according to wiring diagram.
VAS 5258 probe 3 + Socket 52
VAS 5258 probe 4 + Socket 53
Wire resistance: max. 1.5 ohms
Note:
Continued for all vehicles.
Using probes 3 and 4 of VAS 5258, check wires for short circuit to each other, to vehicle Ground (GND) and to B+.
Specification: infinity ohms
^ Disconnect VAS 5258 from engine harness.
If wiring malfunctions are detected:
^ Locate problem using wiring diagram and repair using VAS 1978 repair kit.
If no wiring malfunctions are detected:
^ Proceed to "-G62- Resistance Measurement".
-G62- Resistance Measurement
Tip:
If -G62- sensor was already replaced in preceding steps, skip this step and continue to second read readiness code step (see below).
Perform resistance measurement on Engine Coolant Temperature (ECT) Sensor -G62-.
^ Connect correct VAS 5258 connector to ECT sensor.
^ Disconnect VAS 5258 from engine harness.
^ Connect Multimeter to VAS 5258 test probes 3 and 4.
Scale A shows resistance values for temperature range 0-50°C (32-122°F).
Scale B shows values for temperature range 50-100°C (122°F-212°F).
Examples:
30°C (86°F) corresponds to a resistance from 1.5 to 2.0 k ohms.
80°C (176°F) corresponds to a resistance from 275 to 375 ohms.
If the specification is not obtained:
^ Replace Engine Coolant Temperature (ECT) sensor -G62-. See ElsaWeb.
^ Check DTC memory, if necessary, repair any malfunctions and then erase DTC memory.
^ Read readiness code. If DTC memory has been erased, readiness code must be generated.
If there is no malfunction in the wiring and the resistance measurement values are valid:
^ Replace Engine Coolant Temperature (ECT) sensor -G62-. See ElsaWeb.
^ Read readiness code. If DTC memory has been erased, readiness code must be generated.
Note:
If DTCs P1296, P2181, P0128 or P3081 are occurring without electrical faults (P0116-P0118) and replacement of Engine Coolant Temperature Sensor -G62- and its terminals repaired, check thermostat and cooling system for proper operation. Ensure fan control unit part no. is valid for vehicle, if equipped. Always see ETKA for the latest part(s) information.
Warranty
Information only.
Required Parts and Tools