Engine Coolant Temperature Sensor 1, 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 Motronic 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
-- Observe safety precautions. Refer to SAFETY PRECAUTIONS
-- Observe Clean Working Conditions. Refer to CLEAN WORKING CONDITIONS
-- 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 indication remains at approx. -40.0° C:
-- Continue test according to the following table:
| Indicated | Cause | Test |
|---|---|---|
| approx. - 40.0° C | Open circuit or short circuit to voltage | ENGINE COOLANT TEMPERATURE SENSOR 1, CHECKING |
| approx. 140.0° C | Short circuit to Ground | ENGINE COOLANT TEMPERATURE SENSOR 1, CHECKING |
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- Refer to the Repair information.
Checking internal resistance
-- Disconnect the Engine Coolant Temperature (ECT) Sensor -G62- electrical harness connector.
-- 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:
Specified values:
| ECT Temperature vs Resistance | ||
| Temp (C) | min. value ohms | max. value ohms |
| - 40 | 36816 | 43714 |
| - 35 | 28840 | 33978 |
| - 25 | 17680 | 20530 |
| - 15 | 10940 | 12534 |
| - 5 | 6897 | 7804 |
| 0 | 5535 | 6226 |
| 5 | 4443 | 4970 |
| 15 | 2923 | 3235 |
| 25 | 1978 | 2167 |
| 35 | 1369 | 1486 |
| 45 | 965 | 1039 |
| 55 | 692 | 738 |
| 65 | 503 | 533 |
| 75 | 372 | 392 |
| 85 | 279 | 292 |
| 95 | 213 | 223 |
| 105 | 164 | 172 |
| 115 | 127 | 134 |
| 125 | 99 | 106 |
| 135 | 78 | 84 |
If the specified values were Not obtained:
-- Replace the Engine Coolant Temperature (ECT) Sensor - G62- Refer to the Repair information.