Electric Cooling Fan Diagnosis Functional Check
| Table 1: | Fan Relay Operation Matrix |
Refer to
Coolant Fans/Relays
for
wiring view.
Circuit Description
To determine if a fault is present perform the Cooling Fan Functional Check. If DTC P1660 is set, or sets during the functional check, it must be diagnosed before proceeding with any of the symptom tables. When the PCM commands low speed fan operation it grounds Cooling Fan Relay 1 which allows current to flow through both cooling fans in a series circuit to ground. If the PCM commands high speed fan operation it grounds all the cooling fan relays, including Fan Relay 1, which changes the circuit to a parallel circuit to ground. If a fault occurs certain symptoms will occur due to the series/parallel circuit design.
The PCM will command fan operation when:
| • | Low Speed Fan Operation |
| - | Engine coolant temperature exceeds approximately 106°C (229°F). |
| - | Transmission fluid temperature exceeds 150°C (302°F). |
| - | A/C operation is requested. |
| - | After the vehicle is shut OFF if the coolant temperature at key-off is more than 151°C (304°F) and system voltage was more than 12 volts. The fans will stay ON for approximately 3 minutes. |
The fans will switch from low to OFF when the coolant drops below 102°C (216°F).
| • | High Speed Fan Operation |
| - | Engine coolant temperature reaches 112°C (234°F). |
| - | Transmission temperature is more than 151°C (304°F). |
| - | When certain DTCs set. |
The fans will switch from high to low (except DTCs set) when the coolant drops below 106°C (229°F).
| • | If the cooling fans operate when commanded OFF and DTC P1660 is not set either a cooling fan relay is stuck ON or a cooling fan circuit is shorted to power. |
| • | Whenever a repair is completed repeat the Cooling Fan Functional Check. This will help diagnose possible multiple failures, for example: two water contaminated relays. |
Operational Mode | OFF | LOW FANS | HIGH FANS |
Low Speed Cooling Fan Relay (#1) | De-Energized | Energized | Energized |
Series/ Parallel Cooling Fan Relay (#2) | De-Energized | De-Energized | Energized |
High Speed Cooling Fan (#3) | De-Energized | De-Energized | Energized |
*The Series/Parallel Cooling Fan Relay is a dual position switch and while de-energized, supplies a ground path for the low speed fan circuit. | |||
Test Description
Number(s) below refer to the step number(s) on the Functional Table.
-
The Powertrain OBD System Check must be performed first so that mis-diagnosis is avoided, due to the PCM commanding the fans ON due to a DTC set, etc.
-
Checking to see if there is a fault on the cooling fan relay control circuits.
-
Checking to see if any A/C DTCs will set. If A/C DTCs set they must be diagnosed before proceeding with the Cooling Fan Functional Check.
-
Commanding fans ON in sequence to determine the symptom (fault-if any) present.
Step | Action | Value(s) | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to A Powertrain On Board Diagnostic (OBD) System Check | ||||||||
Did the Driver 1 display ever indicate a FAULT? | 5°C - 100°C (41°F - 212°F) | Go to DTC P1660 Cooling Fan Control Circuits | ||||||||
With the engine idling turn A/C ON to maximum cooling. Have any other DTC(s) failed this ignition? | -- | Go to DTC(s) that are set | ||||||||
4 |
Does the test lamp illuminate on both terminals? | -- | ||||||||
Do both cooling fans operate as commanded? | 100°C (212°F) | System OK | ||||||||
6 | Does only Cooling Fan #1 (left) operate with Fan Relay 1 commanded ON then both fans operate when All Relays are commanded ON? | -- | ||||||||
7 | Repair CKT 504 shorted to ground. Is the repair complete? | -- | -- | |||||||
8 | Does neither cooling fan operate with Fan Relay 1 commanded ON then only Cooling Fan #2 (right) operate with All Relays commanded ON? | -- | Go to Electric Cooling Fan Diagnosis (Symptom Tables) (Table 1) | |||||||
9 | Does neither cooling fan operate with Fan Relay 1 commanded ON then only Cooling Fan #1 (left) operate with All Relays commanded ON? | -- | Go to Electric Cooling Fan Diagnosis (Symptom Tables) (Table 2) | |||||||
10 | Do both cooling fans operate with Fan Relay 1 commanded ON then only Cooling Fan #2 (right) operate with All Relays commanded ON? | -- | Go to Electric Cooling Fan Diagnosis (Symptom Tables) (Table 3) | |||||||
11 | Do both cooling fans operate with Fan Relay 1 commanded ON then only Cooling Fan #1 (left) operate with All Relays commanded ON? | -- | Go to Electric Cooling Fan Diagnosis (Symptom Tables) (Table 4) | |||||||
12 | Does neither cooling fan operate when Fan Relay 1 is commanded ON and also when All Relays are commanded ON? | -- | Go to Electric Cooling Fan Diagnosis (Symptom Tables) (Table 5) | |||||||
13 | Does either cooling fan operate when All Relays is commanded OFF? | -- | Go to Diagnostic Aids | |||||||
14 | Repair the cause of no voltage. Possible cause include the following:
Is the repair complete? | -- | -- |
Electric Cooling Fan Diagnosis Symptom Tables
