Engine Coolant Temperature Sensor Checking: Notes
- Cooling system is under pressure.
- Danger of scalding when opening!
Use only gold-plated terminals when servicing terminals in the electrical harness connector of Engine Coolant Temperature (ECT) Sensor -G62-.
Special tools and workshop equipment required
- Multimeter.
- Jumper wire.
- Wiring diagram.
Test requirements
- The Engine Control Module (ECM) - J623- fuses OK.
- Battery voltage at least 12.5 volts.
- All electrical consumers such as, lights and rear window defroster, switched off.
- Vehicles with automatic transmission, shift selector lever into position "P" or "N".
- A/C switched off.
- Ground connections between engine/transmission/chassis OK.
- Ignition switched off.
- Engine cold.
Test procedure
-- Perform a preliminary check to verify the customers complaint. Refer to PRELIMINARY CHECK .
Start diagnosis
-- Connect the scan tool.
-- Switch the ignition On.
-- Using the scan tool, check the coolant temperature:
| Diagnostic text | Specified value | |||
|---|---|---|---|---|
| Coolant temperature | Approx. coolant temperature | |||
If the specified value is not obtained:
-- Continue test according to the following table:
| Indicated | Cause | Test |
|---|---|---|
| approx. -40.0°C | Open circuit or short circuit to (B+) | TESTING IF DISPLAY IS APPROX. - 40.0°C: |
| approx. 140.0°C | Short circuit to Ground | TESTING IF DISPLAY APPROX. 140.0°C: |
If the specified value was obtained:
-- Start the engine and let it run at idle.
The temperature value must increase uniformly 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.
-- Replace the Engine Coolant Temperature (ECT) Sensor - G62-.
Checking internal resistance
-- Disconnect the Engine Coolant Temperature (ECT) Sensor -G62- electrical harness connector -arrow-.
-- Using a multimeter, check the Engine Coolant Temperature (ECT) Sensor -G62- terminals 1 to 2 for resistance.
Use the chart below for the specified values:
- Area A: Resistance values 0 to 50°C.
- Area B: Resistance values 50 to 100°C.
Specified values:
- Range A, 30°C equals a resistance of 1.5 to 2.0 K Ω
- Range B, 80°C equals a resistance of 275 to 375 Ω
If any of the specified values were Not obtained:
-- Replace the Engine Coolant Temperature (ECT) Sensor - G62-.