Refer to
Cell 31
for wiring diagrams.
Circuit Description:
Power for the fan motors is supplied through the Cooling Fan fuse in the LH Maxi fuse block. The cooling fan relays are energized when current flows from the Cooling Fan fuse in the IP fuse block through the relay coils to ground through the PCM. The low speed cooling fan relay control circuit is grounded for low speed fan operation. The low speed cooling fan relay and the high speed cooling fan relay control circuits are grounded for high speed operation.
During low speed fan operation the PCM supplies a ground path for the low speed cooling fan relay. This closes the low speed relay contacts, allowing current to flow directly to the R.H. cooling fan and through a resistor to the L.H. cooling fan.
During high speed cooling fan operation the PCM enables both relays, supplying current directly to both cooling fans.
Diagnostic Aids
Check for the following conditions:
| • | Poor connection at the PCM, cooling fan relays, or cooling fan motors. |
| Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection. |
| • | Damaged harness. |
| Inspect the wiring harness for damage. Refer to Intermittents and Poor Connections Diagnosis . |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
Stored diagnostic trouble codes may affect engine cooling fan operation. This diagnostic table may lead to improper diagnosis and replacement of good parts if diagnostic trouble codes are present.
-
Ambient temperature must be greater than 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 ambient temperature.
-
This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed.
Step | Action | Value(s) | Yes | No | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | ||||||||||
Are any PCM DTCs stored? | -- | Diagnose the DTCs first - Go to Powertrain Control Module Diagnosis | ||||||||||
3 |
Observe the cooling fans. Are the cooling fans running? | -- | ||||||||||
4 | With a scan tool, command Fan 1 ON. Do both cooling fans operate? | -- | ||||||||||
5 | With a scan tool, command Fan 2 ON. Does the left side cooling fan run at high speed? | -- | ||||||||||
|
Important: Ambient temperature must be greater than 9°C (48°F).
Are the cooling fans running? | -- | System OK For Intermittent - Go to Diagnostic Aids | ||||||||||
7 | View the A/C Request display on the scan tool. Does the scan tool display Yes? | -- | Go to Powertrain Control Module Controlled Air Conditioning (A/C) Circuit Diagnosis | |||||||||
8 |
Does the test lamp illuminate? | -- | ||||||||||
9 | Probe low speed cooling fan relay switch feed circuit using a test lamp that is connected to a good ground. Does the test lamp illuminate? | -- | ||||||||||
10 |
Are both cooling fans running? | -- | ||||||||||
11 |
Does the test lamp illuminate? | -- | ||||||||||
12 |
Did you find and correct the condition? | -- | ||||||||||
13 |
Did you find and correct the condition? | -- | ||||||||||
14 |
Does the test lamp illuminate when probing each circuit? | -- | ||||||||||
15 | Connect the test lamp between fan feed and ground terminals at both cooling fan connectors. Does the test lamp illuminate at both cooling fan connectors? | -- | ||||||||||
16 | Locate and repair open in fan feed circuit. Refer to Wiring Repairs . Is the action complete? | -- | -- | |||||||||
17 | Locate and repair open in the ground circuit to the affected cooling fan motor(s). Refer to Wiring Repairs . Is the action complete? | -- | -- | |||||||||
18 |
Does the test lamp illuminate? | -- | ||||||||||
19 | Probe high speed cooling fan relay coil feed circuit with a test lamp that is connected to a good ground. Does the test lamp illuminate? | -- | ||||||||||
20 |
Does the left side cooling fan run at high speed? | -- | ||||||||||
21 |
Does the test lamp illuminate? | -- | ||||||||||
22 |
Did you find and correct the condition? | -- | ||||||||||
23 |
Did you find and correct the condition? | -- | ||||||||||
24 |
Does the test lamp illuminate? | -- | ||||||||||
25 | Connect a test lamp between left side cooling fan high speed feed circuit and the fan ground circuit. Does the test lamp illuminate? | -- | ||||||||||
26 | Locate and repair the open in the ground circuit to the left side cooling fan motor. Refer to Wiring Repairs . Is the action complete? | -- | -- | |||||||||
27 | Locate and repair open in high speed fan feed to the left side cooling fan. Refer to Wiring Repairs . Is the action complete? | -- | -- | |||||||||
28 | Locate and repair open in ignition feed (CKT 241) to the affected cooling fan relay. Refer to Wiring Repairs . Is action complete? | -- | -- | |||||||||
29 | Locate and repair cause of no battery feed to the affected fan relay switch feed:
Refer to Wiring Repairs . Is the action complete? | -- | -- | |||||||||
30 | Disconnect the high speed cooling fan relay. Is either cooling fan running? | -- | ||||||||||
31 | Probe the high speed cooling fan relay control circuit with a test lamp that is connected to B+. Does the test lamp illuminate? | -- | ||||||||||
32 | With a scan tool, observe the A/C High Side Pressure. Is the A/C High Side Pressure greater than the specified value? | 1.5V | Go to Diagnostic System Check | |||||||||
33 |
Does the test lamp illuminate? | -- | ||||||||||
34 | Locate and repair the short to ground in the high speed cooling fan relay control circuit. Refer to Wiring Repairs . Is the action complete? | -- | -- | |||||||||
35 | Disconnect the low speed cooling fan relay. Is either cooling fan ON? | -- | ||||||||||
36 | Probe the low speed cooling fan relay control circuit using a test lamp that is connected to B+. Does the test lamp illuminate? | -- | ||||||||||
37 |
Does the test lamp illuminate? | -- | ||||||||||
38 | Locate and repair the short to ground in the low speed cooling fan relay control circuit. Refer to Wiring Repairs . Is the action complete? | -- | -- | |||||||||
39 | Locate and repair short to B+ in affected cooling fan feed circuit. Refer to Wiring Repairs . Is the action complete? | -- | -- | |||||||||
40 |
Did you find and correct the condition? | -- | ||||||||||
41 | Replace the low speed cooling fan relay. Is the action complete? | -- | -- | |||||||||
42 |
Did you find and correct the condition? | -- | ||||||||||
43 | Replace the high speed cooling fan relay. Is the action complete? | -- | -- | |||||||||
|
Important: The replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Is the action complete? | -- | -- | ||||||||||
45 | Test for poor connections. If OK, then replace the affected cooling fan motor. Is the action complete? | -- | -- | |||||||||
46 |
Are the cooling fans running? | -- | ||||||||||
47 | With a scan tool, command Fan 1 ON. Do both cooling fans run at low speed? | -- | ||||||||||
48 | With a scan tool, command Fan 2 ON. Does the left side cooling fan run at high speed? | -- | System OK |
