| Table 1: | Engine Cooling Fan Relay Circuit |
Circuit Description
The powertrain control module (PCM) controls the cooling fan motor through the cooling fan relay. The PCM receives engine coolant temperature readings from the engine coolant temperature (ECT) sensor. The PCM uses the ECT sensor in order to control the cooling fan. The PCM provides a ground path for the control circuit to the cooling fan relay. The PCM turns ON the cooling fan when the engine coolant temperature rises above 97.5°C (208°F). The PCM turns OFF the cooling fan when the engine coolant temperature drops below 92.5°C (199°F).
Conditions for Setting the DTC
| • | Low voltage is indicated at the control terminal of the cooling fan relay |
| • | The engine coolant temperature is below 92.5°C (199°F). |
| • | The condition is present for 5 seconds |
Action Taken When the DTC Sets
| • | The PCM illuminates the malfunction indicator lamp (MIL) after two consecutive ignition cycles in which the diagnostic runs with the fault active. |
| • | The PCM records the operating conditions at the time that the diagnostic fails. The Freeze Frame buffer stores this information. |
Conditions for Clearing the MIL/DTC
| • | The MIL turns OFF after three consecutive trips, during which the diagnostic runs and there are not any faults that are detected. |
| • | A History DTC clears after 40 consecutive warm-up cycles without a fault. |
| • | Use the Clear DTC Information function on the scan tool, or disconnect the PCM battery feed in order to clear the DTC. |
Diagnostic Aids
An engine overheating concern may occur with a DTC P0480 condition. An engine overheating concern may be a boil over occurring, or only the illumination of a warning indicator. Check for any of the following conditions:
| • | A malfunctioning engine temperature gauge or a warning lamp may indicate an engine overheating condition when there is not a boil over occurring. Check the temperature gauge or the warning lamp circuits. Check the engine temperature gauge accuracy by comparing the ECT sensor reading on a scan tool with the gauge reading. |
| • | An engine that is close to overheating when the cooling fan turns ON may have a shifted ECT sensor. Check the ECT sensor for correct calibration. Refer to Temperature Versus Resistance . |
| • | An engine that is hot or overheating when the cooling fan is ON may have a faulty cooling system. |
A fault in the engine cooling fan circuit may cause an intermittent malfunction. Inspect the wiring harness and the components for any of the following conditions:
| • | Backed out terminals |
| • | Incorrect mating of terminals |
| • | Broken electrical connector locks |
| • | Incorrectly formed terminals or damaged terminals |
| • | Faulty terminal-to-wire connections |
| • | Physical damage to the wiring harness |
| • | A broken wire inside the insulation |
| • | Corrosion of electrical connections, of splices, or of terminals |
If a DTC P0480 cannot be duplicated, the Freeze Frame data can be useful in determining vehicle operating conditions when the DTC was set.
Use the following relay cavity table in order to locate the correct cavities to probe during diagnosis. The table layout corresponds to the cavity layout of the relay block.
Relay Cavity Identification | |
|---|---|
Switch Power | |
Switch Load | |
Coil Power | Coil Ground |
Test Description
The numbers below refer to the step numbers in the diagnostic table.
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The Powertrain OBD System Check prompts the technician to complete some basic checks, and to save the applicable freeze frame data on the scan tool. This creates an electronic copy of the data that was taken when the fault occurred. The scan tool saves the information for later reference.
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The cooling fan motor should be OFF if the engine coolant temperature is below the specified value. If the cooling fan runs when the ignition is ON, even though the engine is OFF, check for a faulty ECT sensor reading.
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The cooling fan motor should turn ON and OFF with the scan tool commands. The output controls feature on the scan tool will not operate the engine cooling fan if any DTCs are present.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | |||
Is the cooling fan OFF when the engine coolant temperature is below the specified value? | 90°C (194°F) | |||
Did the cooling fan turn ON and OFF with the scan tool? | -- | Go to Diagnostic Aids | ||
4 |
Is the cooling fan OFF? | 90°C (194°F) | ||
5 | Probe the connector cavity 2 of the cooling fan relay with a test lamp connected to B+. Refer to the Relay Cavity Identification table in Diagnostic Aids. Did the test lamp illuminate? | -- | ||
6 | Repair the short to voltage in the power feed circuit between the cooling fan relay and the cooling fan motor. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
7 |
Was a repair necessary | -- | ||
8 |
Did the test lamp illuminate? | -- | ||
9 | Probe the connector cavity 4 of the cooling fan relay with a test lamp to ground. Did the test lamp illuminate? | -- | ||
10 | Connect a fused jumper wire between the connector cavities 3 and 4 of the cooling fan relay. Is the cooling fan motor ON? | -- | ||
11 |
Did the test lamp illuminate? | -- | ||
12 |
Was a repair necessary? | -- | ||
13 |
Was a repair necessary? | -- | ||
14 |
Was a repair necessary? | -- | ||
15 | Repair the open in the ignition feed circuit between the cooling fan relay terminal 1 and the junction block. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
16 | Repair the open in the battery feed circuit between the cooling fan relay terminal 4 and the fuse box. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
17 | Replace the cooling fan relay. Refer to Engine Cooling Fan Relay Replacement . Is the action complete? | -- | -- | |
18 | Replace the PCM. Is the action complete? | -- | -- | |
19 | Replace the cooling fan motor. Refer to Engine Cooling Fan Replacement in Engine Cooling. Is the action complete? | -- | -- | |
20 |
Are any DTCs displayed on the scan tool? | -- | Go to the applicable DTC table | System OK |
