Refer to
Power, Ground, and Cooling Fans
in Engine Controls Schematics.
.
Circuit Description
The electric cooling fans are controlled by the body control module (BCM) which enables the fans through the powertrain control module (PCM). The PCM enables the ground path for the 3 cooling fan relays. The relays are used to control the high current flow to power the cooling fan motors. When minimum cooling is required, the BCM will command the PCM to energize cooling fan relay #1. Since both fans are connected in series through the Mode Control relay, both fans will operate at low speed. When maximum cooling is required, the BCM will command the PCM to energize all 3 cooling fan relays. Power is supplied to the left fan through cooling fan relay #1 and is grounded through the Mode Control relay. The right fan is powered directly through cooling fan relay #2, causing both fans to operate at high speed.
Cooling Fan Run-On
The PCM usually powers down 10 to 30 seconds after the ignition is turned off. Since the cooling fan is PCM controlled, the PCM may remain powered for up to 7 minutes after the ignition is turned off in order to provide a ground to energize the cooling fan relay.
This is called a fan run-on and will occur if any of the following combinations of conditions exist when the ignition is turned off:
| • | The engine coolant temperature (ECT) is more than 100°C (212°F) and the intake air temperature (IAT) is more than 80°C (176°F). |
| • | The ECT is more than 112°C (234°F) and the IAT is more than 70°C (158°F). |
| • | The ECT is more than 116°C (241°F). |
The PCM and the cooling fan will remain on until these combinations of conditions no longer exist, up to a maximum of 7 minutes.
If the cooling fan is off when the PCM powers down, the fan will remain off regardless of temperature until the ignition is turned on again.
Diagnostic Aids
If the owner complained of an overheating problem, determine if the complaint was due to an actual boil over, or the warning indicator lamp. If the engine is actually overheating, but the cooling fan is not coming on, the ECT sensor has probably shifted out of calibration and should be replaced.
If the engine is overheating and the cooling fans are on, the cooling system should be inspected. Refer to Engine Overheating in Engine Cooling.
The body function controller (BFC) will command the PCM to enable the low speed fans on at 106°C (223°F) and off at 103°C (217°F) and the high speed fans on at 111°C (232°F). and off at 108°C (226°F).
Test Description
The numbers below refer to the step numbers on the diagnostic table:
-
Ambient temperature must be above 9°C (48°F) before the PCM will enable the cooling fans due to A/C request. The PCM will enable the cooling fans if A/C refrigerant pressure increases, regardless of the ambient temperature.
-
The replacement PCM must be programmed and the Crankshaft Position System Variation Learn procedure must be performed.
Step | Action | Value(s) | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | |||||||
2 |
Are any PCM DTCs stored? | -- | Go to Step 3 | |||||||
3 |
Are both cooling fans running? | 100°C (212°F) | Go to Step 32 | Go to Step 4 | ||||||
4 |
Is the right or left cooling fan running at low speed? | -- | Go to Step 5 | Go to Step 8 | ||||||
5 |
Are both cooling fans running at high speed? | -- | Go to Step 6 | Go to Step 58 | ||||||
|
Important: The ambient temperature must be above 9°C (48°F).
Are both cooling fans on? | -- | Go to Diagnostic Aids | Go to Step 7 | |||||||
7 | Use a scan tool in order to observe the A/C Request. Does the A/C Request read Yes? | -- | Go to Step 78 | Go to Air Conditioning (A/C) Compressor Control Circuit Diagnosis | ||||||
8 | Are either of the cooling fans running? | -- | Go to Step 9 | Go to Step 16 | ||||||
9 | Is the left cooling fan running? | -- | Go to Step 10 | Go to Step 14 | ||||||
10 |
Is the left cooling fan running? | -- | Go to Step 11 | Go to Step 81 | ||||||
11 | Remove the mode control relay. Refer to Air Conditioning (A/C) Compressor and Cooling Fan Relays Replacement in HVAC. Is the left cooling fan running? | -- | Go to Step 12 | Go to Step 13 | ||||||
12 | Repair the short to ground in the mode control relay to the left cooling fan circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 82 | -- | ||||||
13 |
Did you find and correct the condition? | -- | Go to Step 82 | Go to Step 71 | ||||||
14 |
Is the right cooling fan running? | -- | Go to Step 15 | Go to Step 72 | ||||||
15 |
Did you find and correct the condition? | -- | Go to Step 82 | Go to Step 80 | ||||||
16 |
Important: Use the J 35616 Connector Test Adapter Kit test lead to probe the underhood fuse block. Does the test lamp illuminate? | -- | Go to Step 18 | Go to Step 17 | ||||||
17 | Repair the open in the fuse circuit of the cooling fan #1 . Did you complete the repair? | -- | Go to Step 82 | -- | ||||||
18 |
Important: Use the J 35616 Connector Test Adapter Kit test lead to probe into the underhood fuse block. Does the test lamp illuminate? | -- | Go to Step 20 | Go to Step 19 | ||||||
19 | Repair an open in the battery rail power circuit. Did you complete the repair? | -- | Go to Step 82 | -- | ||||||
20 |
Important: Use the J 35616 Connector Test Adapter Kit test lead to probe into the underhood fuse block. Does the test lamp illuminate? | -- | Go to Step 21 | Go to Step 27 | ||||||
21 |
Important: Use the J 35616 Connector Test Adapter Kit test lead to probe into the underhood fuse block. Does the test lamp illuminate? | -- | Go to Step 22 | Go to Step 25 | ||||||
22 |
Important: Use the J 35616 Connector Test Adapter Kit test lead to probe into the underhood fuse block. Are both cooling fans running? | -- | Go to Step 23 | Go to Step 24 | ||||||
23 |
Did you find and correct the condition? | -- | Go to Step 82 | Go to Step 37 | ||||||
24 |
Did you find and correct the condition? | -- | Go to Step 82 | Go to Step 64 | ||||||
25 |
Important: Use the J 35616 Connector Test Adapter Kit test lead to probe into the underhood fuse block. Does the test lamp illuminate? | -- | Go to Step 78 | Go to Step 26 | ||||||
26 |
Did you find and correct the condition? | -- | Go to Step 82 | -- | ||||||
27 |
Important: Use the J 35616 Connector Test Adapter Kit test lead to probe into the underhood fuse block. Important: Use the J 35616 Connector Test Adapter Kit test lead to probe into the underhood fuse block. Does the test lamp illuminate? | -- | Go to Step 28 | Go to Step 31 | ||||||
28 |
Important: Use the J 35616 Connector Test Adapter Kit test lead to probe into the underhood fuse block. Connect a test lamp between the mode control relay cavity 30 and cavity 87A in the underhood fuse block. Does the test lamp illuminate? | -- | Go to Step 30 | Go to Step 29 | ||||||
29 |
Did you find and correct the condition? | -- | Go to Step 82 | Go to Step 57 | ||||||
30 |
Did you find and correct the condition? | -- | Go to Step 82 | Go to Step 71 | ||||||
31 |
Did you find and correct the condition? | -- | Go to Step 82 | Go to Step 56 | ||||||
32 | Use a scan tool in order to observe the A/C Request. Does the A/C request read Yes? | -- | Go to Air Conditioning (A/C) Compressor Control Circuit Diagnosis | Go to Step 33 | ||||||
33 | Are both cooling fans running at low speed? | -- | Go to Step 34 | Go to Step 40 | ||||||
34 | Remove the fan control relay #1. Refer to Air Conditioning (A/C) Compressor and Cooling Fan Relays Replacement . Are the cooling fans running? | -- | Go to Step 35 | Go to Step 36 | ||||||
35 |
Did you find and correct the condition? | -- | Go to Step 82 | -- | ||||||
36 |
Important: Use the J 35616 Connector Test Adapter Kit test lead to probe into the underhood fuse block. Does the test lamp illuminate? | -- | Go to Step 38 | Go to Step 37 | ||||||
37 | Replace the fan control relay #1. Refer to Air Conditioning (A/C) Compressor and Cooling Fan Relays Replacement . Did you complete the repair? | -- | Go to Step 82 | -- | ||||||
38 |
Important: Use the J 35616 Connector Test Adapter Kit test lead to probe into the underhood fuse block. Does the test lamp illuminate? | -- | Go to Step 39 | Go to Step 78 | ||||||
39 |
Did you find and correct the condition? | -- | Go to Step 82 | -- | ||||||
40 | Are both cooling fans running at high speed? | -- | Go to Step 41 | Go to Step 42 | ||||||
41 | Use a scan tool in order to observe the A/C Pressure voltage. Is the voltage less than the specified value? | 1.2 V | Go to Step 78 | Go to Step 44 | ||||||
42 |
Is the right cooling fan running at high speed? | -- | Go to Step 43 | Go to Step 78 | ||||||
43 |
Did you find and correct the condition? | -- | Go to Step 82 | Go to Step 52 | ||||||
44 |
Is the voltage approximately equal to the specified value? | 0.0 V | Go to Step 46 | Go to Step 45 | ||||||
45 |
Does the voltage approximately equal the specified value? | 0.0 V | Go to Step 78 | Go to Step 51 | ||||||
46 |
Does the test lamp illuminate? | -- | Go to Step 47 | Go to Step 49 | ||||||
47 |
Does the voltage approximately equal the specified value? | 5.0 V | Go to Step 48 | Go to Step 50 | ||||||
48 | Replace the A/C pressure sensor. Refer to Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement in HVAC Systems. Did you complete the repair? | -- | Go to Step 82 | -- | ||||||
49 |
Did you find and correct the condition? | -- | Go to Step 82 | -- | ||||||
50 |
Did you find and correct the condition? | -- | Go to Step 82 | -- | ||||||
51 |
Did you find and correct the condition? | -- | Go to Step 82 | -- | ||||||
52 |
Is the right cooling fan running at high speed? | -- | Go to Step 53 | Go to Step 71 | ||||||
53 | Remove the fan control relay #2. Refer to Air Conditioning (A/C) Compressor and Cooling Fan Relays Replacement . Is the right cooling fan running at high speed? | -- | Go to Step 54 | Go to Step 55 | ||||||
54 |
Did you find and correct the condition? | -- | Go to Step 82 | -- | ||||||
55 |
Did you find and correct the condition? | -- | Go to Step 82 | Go to Step 77 | ||||||
56 |
Did you find and correct the condition? | -- | Go to Step 82 | Go to Step 80 | ||||||
57 |
Did you find and correct the condition? | -- | Go to Step 82 | Go to Step 81 | ||||||
58 | Remove the mode control relay. Refer to Air Conditioning (A/C) Compressor and Cooling Fan Relays Replacement . Do the cooling fan motors turn off? | -- | Go to Step 62 | Go to Step 59 | ||||||
59 |
Important: Use the J 35616 Connector Test Adapter Kit test lead to probe into the underhood fuse block. Does the test lamp illuminate? | -- | Go to Step 62 | Go to Step 60 | ||||||
60 |
Important: Use the J 35616 Connector Test Adapter Kit test lead to probe into the underhood fuse block. Does the test lamp illuminate? | -- | Go to Step 79 | Go to Step 61 | ||||||
61 |
Did you find and correct the condition? | -- | Go to Step 82 | Go to Step 78 | ||||||
62 |
Does the test lamp illuminate? | -- | Go to Step 63 | Go to Step 65 | ||||||
63 |
Does the test lamp illuminate? | -- | Go to Step 64 | Go to Step 72 | ||||||
64 |
Did you find and correct the condition? | -- | Go to Step 82 | -- | ||||||
65 |
Important: Use the J 35616 Connector Test Adapter Kit test lead to probe into the underhood fuse block. Does the test lamp illuminate? | -- | Go to Step 67 | Go to Step 66 | ||||||
66 |
Did you find and correct the condition? | -- | Go to Step 82 | -- | ||||||
67 |
Important: Use the J 35616 Connector Test Adapter Kit test lead to probe into the underhood fuse block. Does the test lamp illuminate? | -- | Go to Step 69 | Go to Step 68 | ||||||
68 |
Did you find and correct the condition? | -- | Go to Step 82 | -- | ||||||
69 |
Did you find and correct the condition? | -- | Go to Step 82 | Go to Step 70 | ||||||
70 |
Did you find and correct the condition? | -- | Go to Step 82 | Go to Step 71 | ||||||
71 | Replace the mode control relay. Refer to Air Conditioning (A/C) Compressor and Cooling Fan Relays Replacement . Did you complete the repair? | -- | Go to Step 82 | -- | ||||||
72 |
Important: Use the J 35616 Connector Test Adapter Kit test lead to probe into the underhood fuse block. Does the test lamp illuminate? | -- | Go to Step 74 | Go to Step 73 | ||||||
73 |
Did you find and correct the condition? | -- | Go to Step 82 | -- | ||||||
74 |
Important: Use the J 35616 Connector Test Adapter Kit test lead to probe into the underhood fuse block. Does the test lamp illuminate? | -- | Go to Step 76 | Go to Step 75 | ||||||
75 |
Did you find and correct the condition? | -- | Go to Step 82 | -- | ||||||
76 |
Did you find and correct the condition? | -- | Go to Step 82 | Go to Step 77 | ||||||
77 | Replace the fan control relay #2. Refer to Air Conditioning (A/C) Compressor and Cooling Fan Relays Replacement . Did you complete the repair? | -- | Go to Step 82 | -- | ||||||
|
Important:: The replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the repair? | -- | Go to Step 82 | -- | |||||||
79 | Repair the open in cavity 85 of the mode control relay and cavity 86 of the control circuit to the PCM for the fan control relay #2 . Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 82 | -- | ||||||
80 | Replace the left cooling fan motor. Refer to Engine Cooling Fan Replacement in HVAC Systems. Did you complete the repair? | -- | Go to Step 82 | -- | ||||||
81 | Replace the right cooling fan motor. Refer to Engine Cooling Fan Replacement . in HVAC Systems Did you complete the repair? | -- | Go to Step 82 | -- | ||||||
82 |
Are both cooling fans running? | 100°C (212°F) | Go to Step 32 | Go to Step 83 | ||||||
83 |
Are both cooling fans running at low speed? | -- | Go to Step 84 | Go to Step 8 | ||||||
84 |
Are both cooling fans running at high speed? | -- | System OK | Go to Step 58 |
