Cooling Fan Circuit Diagnosis Non European Emissions
Circuit Description
The engine cooling fan circuit operates the main cooling fan and the auxiliary cooling fan. The cooling fans are controlled by the engine control module (ECM) based on inputs from the engine coolant temperature (ECT) sensor and the air conditioning pressure (ACP) sensor. The ECM controls the low speed cooling fan operation by internally grounding the ECM connector terminal A10. This energizes the low speed cooling fan relay and operates the main cooling fan at low speed as the cooling fans. The ECM controls the high speed cooling fan operation by internally grounding the ECM connector terminal A14. This energizes the high speed cooling fan relay resulting in high speed fan operation as the cooling fans are now connected in a parallel circuit.
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 fuses EF4 or EF7 become open, immediately after installation, inspect for a short to ground in the wiring of the appropriate circuit. If the fuses become open when the cooling fans are to be turned ON by the ECM, suspect a faulty cooling fan motor. |
| • | The ECM will turn the cooling fans ON at low speed when the coolant temperature is 96°C (205°F). The ECM will turn the cooling fans OFF when the coolant temperature is 93°C (199°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). |
| • | The ECM will turn the cooling fans ON at low speed when the A/C system is ON. The ECM will change the cooling fans from low speed to high speed when the high side A/C pressure is 1938 kPa (28 psi), then return to low speed when the high side A/C pressure is 1510 kPa (219 psi). |
| • | The cooling fan circuit can be inspected quickly by disconnecting the ECM connector and grounding the connector terminal A10. This should create low speed cooling fan operation with the ignition ON. By grounding the ECM connector terminal A14 and turning the ignition ON, high speed cooling fan operation should be achieved. |
Step | Action | Values | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | 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 run 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 1 of the main 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 1 of the main cooling fan connector and ground. Is the repair complete? | -- | System OK | -- | ||||||
11 | Inspect for a damaged terminals in the 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 cases? | -- | Go to Step 14 | Go to Step 13 | ||||||
13 | Repair the power supply circuit.
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 |
Are the resistances equal to the specified value ? | 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. Refer to Relay Replacement . Is the repair complete? | -- | System OK | -- | ||||||
19 |
Is the test light ON? | -- | Go to Step 20 | Go to Step 24 | ||||||
20 | Connect a test light between terminal 1 of the auxiliary cooling fan connector and battery positive. Is the test light ON? | -- | Go to Step 21 | Go to Step 23 | ||||||
21 | Replace the auxiliary cooling fan. Is the repair complete? | -- | System OK | Go to Step 22 | ||||||
22 | Repair an open circuit between the following terminals:
Is the repair complete? | -- | System OK | Go to Step 11 | ||||||
23 | Repair an open circuit between terminal 1 of the auxiliary cooling fan connector and ground. Is the repair complete? | -- | System OK | -- | ||||||
24 |
Is the test light ON for both cases? | -- | Go to Step 26 | Go to Step 25 | ||||||
25 | Repair the open power supply circuit:
Is the repair complete? | -- | System OK | Go to Step 26 | ||||||
26 |
Do the cooling fans run at high speed? | -- | Go to Step 15 | Go to Step 27 | ||||||
27 |
Are the resistances equal to the specified value ? | 0 ohms | Go to Step 29 | Go to Step 28 | ||||||
28 | Repair the open circuit between the specific circuit wiring. Is the repair complete? | -- | System OK | -- | ||||||
29 | Replace the high speed cooling fan relay. Refer to Relay Replacement . Is the repair complete? | -- | System OK | Go to Step 15 |
Cooling Fan Circuit Diagnosis European
Circuit Description
The engine cooling fan circuit operates the main cooling fan and the auxiliary cooling fan. The cooling fans are controlled by the engine control module (ECM) based on inputs from the engine coolant temperature (ECT) sensor and the air conditioning pressure (ACP) sensor. The ECM controls the low speed cooling fan operation by internally grounding the ECM connector terminal K28. This energizes the low speed cooling fan relay and operates the main cooling fan at low speed as the cooling fans. The ECM controls the high speed cooling fan operation by internally grounding the ECM connector terminal K12. This energizes the high speed cooling fan relay resulting in high speed fan operation as the cooling fans are now connected in a parallel circuit.
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 fuses Ef4 or Ef7 becomes open immediately after installation, inspect for a short to ground in the wiring of the appropriate circuit. If the fuses become open when the cooling fans are to be turned ON by the ECM, suspect a faulty cooling fan motor. |
| • | The ECM will turn the cooling fans ON at low speed when the coolant temperature is 97°C (207°F). The ECM will turn the cooling fans OFF when the coolant temperature is 94°C (201°F). |
| • | The ECM will turn the cooling fans ON at high speed when the coolant temperature is 101°C (214°F). The ECM will change the cooling fans from high speed to low speed when the coolant temperature is 98°C (208°F). |
| • | The ECM will turn the cooling fans ON at low speed when the A/C system is ON. The ECM will change the cooling fans from low speed to high speed when the high side A/C pressure is 1 859 kPa (269, psi) then return to low speed when the high side A/C pressure is 1 449 kPa (210 psi). |
| • | The cooling fan circuit can be inspected quickly by disconnecting the ECM connector and grounding the connector terminal K28. This should create low speed cooling fan operation with the ignition switch ON. By grounding the ECM connector terminals K12 and turning the ignition switch to ON, high speed cooling fan operation should be achieved. |
Step | Action | Values | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | 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 101°C (214°F). Do the cooling fans run at high speed? | -- | Go to Step 5 | Go to Step 19 | ||||
5 |
Does the cooling fan run 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 |
Does the test light illuminate? | -- | Go to Step 9 | Go to Step 12 | ||||
9 | Connect a test light between the main cooling fan connector terminal 1 and the battery positive terminal. Does the test light illuminate? | -- | Go to Step 11 | Go to Step 10 | ||||
10 | Repair the open circuit between the main cooling fan connector terminal 1 and ground. Is the repair complete? | -- | System OK | -- | ||||
11 | Inspect for a damaged terminal in the 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 cases? | -- | Go to Step 14 | Go to Step 13 | ||||
13 | Repair the power supply circuit.
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 replacement complete? | -- | System OK | -- | ||||
16 |
Is the resistance the specified value? | 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 |
Does the test light illuminate? | -- | Go to Step 20 | Go to Step 24 | ||||
20 | Connect a test light between the auxiliary cooling fan connector terminal 1 and the battery positive terminal. Does the test light illuminate? | -- | Go to Step 21 | Go to Step 23 | ||||
21 | Replace the auxiliary cooling fan. Is the replacement complete? | -- | System OK | Go to Step 22 | ||||
22 | Repair an open circuit between the following terminals:
Is the repair complete? | -- | System OK | Go to Step 11 | ||||
23 | Repair an open circuit between the auxiliary cooling fan connector terminal 1 and ground. Is the repair complete? | -- | System OK | -- | ||||
24 |
Does the test light illuminate for both cases? | -- | Go to Step 26 | Go to Step 25 | ||||
25 | Repair the open power supply circuit:
Is the repair complete? | -- | System OK | Go to Step 26 | ||||
26 |
Does the cooling fans run at high speed? | -- | Go to Step 15 | Go to Step 27 | ||||
27 |
Is the resistance equal to the specified value? | 0 ohms | Go to Step 29 | Go to Step 28 | ||||
28 | Repair the open circuit between the specific circuit wiring. Is the repair complete? | -- | System OK | -- | ||||
29 | Replace the high speed cooling fan relay. Refer to Relay Replacement . Is the replacement complete? | -- | System OK | Go to Step 15 |
Cooling Fan Circuit Diagnosis North American Emissions
Circuit Description
The engine cooling fan circuit operates the main cooling fan and the auxiliary cooling fan. The cooling fans are controlled by the engine control module (ECM) based on inputs from the engine coolant temperature (ECT) sensor and the air conditioning pressure (ACP) sensor. The ECM controls the low speed cooling fan operation by internally grounding the ECM connector terminal 93. This energizes the low speed cooling fan relay and operates the main cooling fan at low speed as the cooling fans. The ECM controls the high speed cooling fan operation by internally grounding the ECM connector terminals 93 and 102 at the same time. This energizes the high speed cooling fan relay resulting in high speed fan operation as the cooling fans are now connected in a parallel circuit.
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 fuses EF4 or EF7 become open, immediately after installation, inspect for a short to ground in the wiring of the appropriate circuit. If the fuses become open when the cooling fans are to be turned ON by the ECM, suspect a faulty cooling fan motor. |
| • | The ECM will turn the cooling fans ON at low speed when the coolant temperature is 96°C (205°F). |
| • | The ECM will turn the cooling fans ON at high speed when the coolant temperature is 99°C (210°F). |
| • | The ECM will turn the cooling fans ON at low speed when the A/C system is ON. The ECM will change the cooling fans from low speed to high speed when the high side A/C pressure is 1 862 kPa (270 psi), then return to low speed when the high side A/C pressure is 1 449 kPa (210 psi). |
| • | The cooling fan circuit can be inspected quickly by disconnecting the ECM connector and grounding the connector terminal 93. This should create low speed cooling fan operation with the ignition ON. By grounding the ECM connector terminals 93 and 102 and turning the ignition ON, high speed cooling fan operation should be achieved. |
Step | Action | Values | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |
2 |
Are the fuses OK? | -- | Go to Step 3 | Go to Diagnostic Aids |
3 |
Is the fuse OK? | -- | Go to Step 4 | Go to Diagnostic Aids |
4 |
Do the cooling fans run at low speed? | 96°C (205°F) | Go to Step 5 | Go to Step 10 |
5 |
Does the cooling fan run at high speed? | 99°C (210°F) | Go to Step 6 | Go to Step 33 |
6 |
Does the A/C compressor clutch engage? | -- | Go to Step 8 | Go to Step 7 |
7 |
Does the A/C compressor clutch engage? | -- | Go to Step 8 | -- |
8 | Do the cooling fans run at low speed? | -- | Go to Step 9 | Go to Step 31 |
9 |
Do the cooling fans run at high speed? | 1 862 kPa (270 psi) | System OK | -- |
10 |
Is the test light ON? | -- | Go to Step 11 | Go to Step 12 |
11 |
Is the test light ON? | -- | Go to Step 28 | Go to Step 17 |
12 |
Is the test light ON? | -- | Go to Step 13 | Go to Step 24 |
13 |
Do the cooling fans run at low speed? | -- | Go to Step 30 | Go to Step 14 |
14 | Inspect for an open wire between the low speed cooling fan relay connector terminal 86 and the engine control module (ECM) connector terminal 93. Is the condition found? | -- | Go to Step 25 | Go to Step 15 |
15 |
Is the test light ON? | -- | Go to Step 16 | Go to Step 23 |
16 | Connect a fused jumper between the low speed cooling fan relay connector terminals 30 and 87. Do the cooling fans run at low speed? | -- | Go to Step 26 | Go to Step 17 |
17 |
Do the cooling fans run at low speed? | 0 ohms | Go to Step 27 | Go to Step 18 |
18 | Inspect the wire between the low speed cooling fan relay connector terminal 87 to the auxiliary cooling fan connector terminal 2 for an open. Is the condition found? | -- | Go to Step 26 | Go to Step 17 |
19 | Inspect the wire between the auxiliary cooling fan connector terminal 1 and the cooling fan control relay connector terminal 30 for an open. Is the condition found? | -- | Go to Step 22 | Go to Step 20 |
20 | Inspect the wire between the cooling fan control relay connector terminal 87a and the main cooling fan connector terminal 2 for an open. Is the condition found? | -- | Go to Step 22 | Go to Step 21 |
21 | Inspect for an open wire between the main cooling fan connector terminal 1 and ground. Is the condition found? | -- | Go to Step 22 | Go to Step 29 |
22 | Repair the open wire as needed. Is the repair complete? | -- | System OK | -- |
23 | Repair the open between the low speed cooling fan relay connector terminal 30 and the battery. Is the repair complete? | -- | System OK | -- |
24 | Repair the open between the low speed cooling fan relay connector terminal 85 and the ignition switch. Is the repair complete? | -- | System OK | -- |
25 | Repair the open wire between the low speed cooling fan relay connector terminal 86 and the ECM connector terminal 93. Is the repair complete? | -- | System OK | -- |
26 | Replace the low speed cooling fan relay. Is the replacement complete? | -- | System OK | -- |
27 | Replace the cooling fan control relay. Is the replacement complete? | -- | System OK | -- |
28 | Replace the auxiliary cooling fan. Is the replacement complete? | -- | System OK | -- |
29 | Replace the ECM. Is the replacement complete? | -- | System OK | -- |
30 |
Is the test light ON? | -- | Go to Step 31 | Go to Step 12 |
31 |
Is the test light ON? | -- | Go to Step 33 | Go to Step 43 |
32 |
Is the test light ON? | -- | Go to Step 33 | Go to Step 43 |
33 |
Is the test light ON? | -- | Go to Step 34 | Go to Step 44 |
34 |
Is the test light ON? | -- | Go to Step 35 | Go to Step 45 |
35 |
Is the test light ON? | -- | Go to Step 36 | Go to Step 46 |
36 |
Do the cooling fans run at high speed? | -- | Go to Step 29 | Go to Step 37 |
37 |
Is the condition found? | -- | Go to Step 22 | Go to Step 38 |
38 |
Is the test light ON? | -- | Go to Step 39 | Go to Step 47 |
39 |
Is the test light ON? | -- | Go to Step 40 | Go to Step 48 |
40 |
Do the cooling fans run at high speed? | -- | Go to Step 42 | Go to Step 41 |
41 |
Do the cooling fans run at high speed? | -- | Go to Step 27 | -- |
42 | Replace the high speed cooling fan relay. Is the replacement complete? | -- | System OK | -- |
43 | Repair the open wire between the high speed cooling fan relay connector terminal 85 and the ignition switch. Is the repair complete? | -- | System OK | -- |
44 | Repair the open wire between the high speed cooling fan relay connector terminal 30 and the battery. Is the repair complete? | -- | System OK | -- |
45 | Repair the open wire between the cooling fan control relay connector terminal 85 and the ignition switch. Is the repair complete? | -- | System OK | -- |
46 | Repair the open wire between the cooling fan control relay connector terminal 87 and ground. Is the repair complete? | -- | System OK | -- |
47 | Repair the open wire between the high speed cooling fan relay connector terminal 87 and the main cooling fan connector terminal 2. Is the repair complete? | -- | System OK | -- |
48 | Repair the open wire between the cooling fan control relay connector terminal 86 and the ECM connector terminal 102. Is the repair complete? | -- | System OK | -- |
