Cooling Fan Circuit Diagnosis 0.8L
Circuit Description
Caution: Refer to Electric Coolant Fan Caution in the Preface section.
The engine cooling fan circuit operates the cooling fan. The cooling fan is controlled by the engine control module (ECM) based on input from the coolant temperature sensor (CTS) and the A/C ON/OFF. The ECM controls the low speed cooling fan operation by internally grounding the ECM connector terminal 39. This energizes the low speed cooling fan relay and operates the cooling fan at low speed. The low speed cooling fan operation is achieved by the cooling fan resistor causing a drop in the voltage supplied to the cooling fan. The ECM controls the high speed cooling fan operation by internally grounding the ECM connector terminal 5. This energizes the high speed cooling fan relay, bypassing the radiator fan resistor. This results in high speed cooling fan operation.
Diagnostic Aids
| • | If the owner complained of an overheating problem, it must be determined if the complaint was due to an actual boil over, or the engine coolant temperature gage indicated overheating. If the engine is overheating and the cooling fans are ON, the cooling system should be inspected. |
| • | If the engine fuse block fuse EF15 becomes open, blown, immediately after installation, inspect for a short to ground in the wiring of the appropriate circuit. If the fuse becomes open, blown when the cooling fans are to be turned ON by the engine control module (ECM), suspect a faulty cooling fan motor. |
| • | The ECM will turn the cooling fan ON at low speed when the coolant temperature is 93°C (199°F). The ECM will turn the cooling fans OFF when the coolant temperature is 90°C (194°F). |
| • | The ECM will turn the cooling fans ON at high speed when the coolant temperature is 100°C (212°F). The ECM will change the cooling fans from high speed to low speed when the coolant temperature is 97°C (207°F). |
Step | Action | Values | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Diagnostic Starting Point-Engine Cooling? | -- | Go to Step 2 | |
2 |
Are the fuses OK? | -- | Go to Step 3 | Go to Diagnostic Aids |
3 |
Does the cooling fan run at low speed? | -- | Go to Step 4 | Go to Step 8 |
4 | The cooling fans should run at high speed when the coolant temperature reaches 100°C (212°F). Do the cooling fans run at high speed? | -- | Go to Step 5 | Go to Step 19 |
5 |
Does the cooling fan runs at low speed? | -- | Go to Step 7 | Go to Step 6 |
6 |
Is the repair complete? | -- | System OK | -- |
7 |
Do the cooling fans run at high speed? | -- | System OK | -- |
8 |
Is the test light ON? | -- | Go to Step 9 | Go to Step 12 |
9 | Connect a test light between terminal 2 of cooling fan connector and battery positive. Is the test light ON? | -- | Go to Step 11 | Go to Step 10 |
10 | Repair the open circuit between terminal 2 of cooling fan connector and ground. Is the repair complete? | -- | System OK | -- |
11 | Inspect for a damaged terminal in main cooling fan connector and repair it or replace the main cooling fan. Is the repair complete? | -- | System OK | -- |
12 |
Is the test light ON for both case? | -- | Go to Step 14 | Go to Step 13 |
13 | Repair power supply circuit fuse EF15 and terminal 30 of the low speed cooling fan relay. Is the repair complete? | -- | System OK | Go to Step 14 |
14 |
Does the cooling fan run at low speed? | -- | Go to Step 15 | Go to Step 16 |
15 | Replace the ECM. Is the repair complete? | -- | System OK | -- |
16 |
Is the resistance within the value specified? | 0 ohms | Go to Step 18 | Go to Step 17 |
17 | Repair the open circuit. Is the repair complete? | -- | System OK | -- |
18 | Replace the low speed cooling fan relay. Is the repair complete? | -- | System OK | -- |
19 | Replace the high speed cooling fan relay. Is the repair complete? | -- | System OK | -- |
