Test requirements
* The Engine Control Module () - 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 → Chapter „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 near Ambient temperature (veh. completely cooled down)
– Switch the ignition Off.
If the specified value was Not obtained:
– Continue test according to the following table:
Indicated Cause Test
approx. - 40.0° C Open circuit or short circuit to (B+) → Anchor
approx. 140.0° C Short circuit to Ground → Anchor
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, if the temperature does not climb uniformly or the temperature signal is intermittent.
– Switch the ignition OFF.
– Replace the the Engine Coolant Temperature () Sensor - G62 or G83- .
Checking internal resistance
– Disconnect the Engine Coolant Temperature () Sensor -G62 or G83- electrical harness connector.
– Using a multimeter, check the Engine Coolant Temperature () Sensor -G62 or G83- terminals 1 to 2 for resistance.
Use the chart below for the specified values:
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 value was Not obtained:
– Replace the Engine Coolant Temperature () Sensor -G62 or G83- .
Testing if display is approx. - 40.0° C
– Disconnect the Engine Coolant Temperature () Sensor -G62 or G83- electrical harness connector .
– Using a jumper wire, connect the Engine Coolant Temperature () Sensor -G62 or G83- electrical harness connector terminals 1 to 2.
– Check the value indicated on the scan tool display.
If the value jumps to approx. 140.0° C:
– Switch the ignition OFF.
– Replace the Engine Coolant Temperature () Sensor -G62 or G83- .
If indication remains at approx. -40.0° C:
Checking wiring
– Remove the Engine Control Module () -J623-. Refer to the Repair Manual.
– Using a multi-meter, check the Engine Coolant Temperature () Sensor -G62 or G83- electrical harness connector terminal 1 to the Engine Control Module () -J623- electrical harness connector for an open circuit or a short to voltage, refer to the chart below for the appropriate sensor. Refer to Wiring Diagrams for pin locations.
1
Engine Coolant Temperature () Sensor -G62 - electrical harness connector terminals Engine Control Module () -J623- electrical connector T60 terminals
1 14
2 10
2
Engine Coolant Temperature () Sensor -2 G83- electrical harness connector terminals Engine Control Module () -J623- electrical connector T94 terminals
1 18
2 12
A TONE GEN TO THESE TERMINALS ABOVE ON T94 WILL LEAD THE WAY!
Specified values: 1.5 Ω Max. and 0 volts disconnected from .
If the specified value was Not obtained:
– Check the wiring for an open or short circuit to Battery (+).
– Check the electrical harness connector for damage, corrosion, loose or broken terminals.
– If necessary, repair the faulty wiring connection.
If no malfunction is detected in the signal circuit:
– Using a multi-meter, check terminal 2 of the sensor to engine ground.
Specified value: 1.5 Ω Max
If the specified value was Not obtained:
– Check the wiring for an open circuit or high resistance.
– Check the electrical harness connector for damage, corrosion, loose or broken terminals.
– If necessary, repair the faulty wiring connection.
If no malfunction is detected in the ground circuit:
– Replace the Engine Control Module () -J623-. Refer to the Repair Manual.
Testing if display approx. 140.0° C
– Disconnect the Engine Coolant Temperature () Sensor -G62 or G83- electrical harness connector .
– Turn the ignition switch ON.
If indication jumps to approx. -40.0° C:
– Switch ignition OFF.
– Replace the Engine Coolant Temperature () Sensor -G62 or G83- .
If indication remains at approx. 140.0° C:
Checking wiring
– Remove the Engine Control Module () -J623-. Refer to the Repair Manual.
– Disconnect the harness connector at the sensor.
– Using a multi-meter, check the signal circuit of the Engine Coolant Temperature () Sensor -G62 or G83- electrical harness connector terminal 1 to engine ground. Refer to Wiring Diagrams for pin locations.
Specified value: OL or no continuity.
If the specified value was Not obtained:
– Check the wiring for a short circuit to Ground.
– Check the electrical harness connector for damage, corrosion, loose or broken terminals.
– If necessary, repair the faulty wiring connection.
If no malfunction is detected in the wiring:
– Replace the Engine Control Module () -J623-. Refer to the Repair Manual.
Final procedures
After the repair work, the following work steps must be performed in the following sequence:
1 - Check the memory. Refer to → Chapter „Diagnostic Mode 03 - Read Memory“.
2 - If necessary, erase the memory. Refer to → Chapter „Diagnostic Mode 04 - Erase Memory“.
3 - If the memory was erased, generate readiness code. Refer to → Chapter „Readiness Code“.