GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 Epica 🢒 Engine 🢒 Engine Controls - 2.5L (LBK) 🢒 DTC P0480 or P0481

Circuit Description

The Cooling Fan Relay 1 or ELEC FAN LOW relay, and Cooling Fan Relay 2 and 3 or ELEC FAN HIGH relay and the ELEC FAN CONT relay are controlled by the engine control module (ECM). The ELEC FAN HIGH relay and the ELEC FAN CONT relay share one control circuit. Battery positive voltage is supplied to the relay coil. The ECM monitors the voltage level on the control circuit of the relay. When the relay is off, voltage level should be near battery voltage on the control circuit of the relay. When the relay is commanded on, voltage level will be low on the control circuit of the relay. The ECM will provide ground on the control circuit of the relay using a low side driver. If the ECM detects a improper voltage level on the control circuit of the relay, a DTC will set.

DTC Descriptor

This diagnostic procedure supports the following DTCs:

    • DTC P0480 Cooling Fan Relay 1 Control Circuit
    • DTC P0481 Cooling Fan Relay 2 and 3 Control Circuit

Conditions for Running the DTC
    • The ignition is ON or the engine is operating.
    • The ignition 1voltage is more than 10 volts.
    • DTCs P0480 and P0481 run continuously once the above conditions are met.

Conditions for Setting the DTC

The ECM detects one of the following conditions on the control circuit of one of the relays for 25 seconds:

    • An open
    • A short to ground
    • A short to voltage

Action Taken When the DTC Sets
    • The control module stores the DTC information into memory when the diagnostic runs and fails.
    • The malfunction indicator lamp (MIL) will not illuminate.
    • The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
    • The driver information center, if equipped, may display a message.

Conditions for Clearing the DTC
    • A current DTC Last Test Failed clears when the diagnostic runs and passes.
    • A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
    • Clear the DTC with a scan tool.

Diagnostic Aids
    • For an intermittent condition, refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
    • The following tables illustrate the ELEC FAN LOW relay, ELEC FAN HIGH relay and the ELEC FAN CONT relay terminal locations in the underhood fuse block:

ELEC FAN LOW Relay Terminal Identification

B+ - Switch

Control

B+ - Coil

Auxiliary Cooling Fan Supply Voltage

Front of Vehicle

ELEC FAN HIGH Relay Terminal Identification

B+ - Switch

Control

B+ - Coil

Main Cooling Fan Supply Voltage

Front of Vehicle

ELEC FAN CONT Relay Terminal Identification

Ground

Control

Main Cooling Fan Supply Voltage

--

B+ - Coil

Voltage from Auxiliary Cooling Fan

Front of Vehicle

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. A test lamp that remains illuminated indicates a short to ground on the control circuit. A test lamp that does not illuminate indicates an open or short to voltage on the control circuit.

    2.

  2. This step tests the control circuit for high resistance.

Step

Action

Values

Yes

No

Schematic Reference: Engine Cooling Schematics

Connector End View Reference: Cooling System Connector End Views

1

Did you perform the Diagnostic System Check - Engine Controls?

--

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2
  1. Turn ON the ignition, with the engine OFF.
  2. With a scan tool, command the Fans Low Speed ON and OFF.

Does the ELEC FAN LOW relay turn ON and OFF with each command?

--

Go to Step 3

Go to Step 4

3

With a scan tool, command the Fans High Speed ON and OFF.

Do the ELEC FAN HIGH and ELEC FAN CONT relays turn ON and OFF with each command?

--

Go to Diagnostic Aids

Go to Step 4

4
  1. Turn OFF the ignition.
  2. Disconnect the affected relay.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the battery positive voltage circuit of the affected relay coil with a test lamp connected to a good ground.

Does the test lamp illuminate?

--

Go to Step 5

Go to Step 13

5
  1. Turn ON the ignition, with the engine OFF.
  2. Probe the control circuit of the affected relay with a test lamp connected to battery positive.
  3. With a scan tool, command the affected relay ON and OFF.

Does the test lamp turn ON and OFF?

--

Go to Step 7

Go to Step 6

6

Does the test lamp remain illuminated?

--

Go to Step 9

Go to Step 10

7
  1. Turn OFF the ignition.
  2. Disconnect the ENG 1 fuse in the underhood fuse block.
  3. Measure the resistance of the battery positive circuit of the affected relay coil from the ENG 1 fuse terminal to the relay terminal.

Is the resistance less than the specified value?

3 ohms

Go to Step 8

Go to Step 13

8
  1. Turn ON the ignition, with the engine OFF.

    2. Important: Use the J 35616-200 Test Lamp Kit for this test. If the J 35616-200 is not available, use a test lamp that measures between 25-30 ohms.

  2. Probe the control circuit of the affected relay with a test lamp connected to battery positive voltage.
  3. With a scan tool, command the affected relay ON.
  4. Measure the voltage from the probe of the test lamp to a good ground with a DMM.

Is the voltage less than the specified value?

2.5 V

Go to Step 11

Go to Step 10

9

Test the control circuit of the affected relay for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 16

Go to Step 12

10

Test the control circuit of the affected relay for one of the following conditions:

    • An open
    • A short to voltage
    • High resistance

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 16

Go to Step 12

11

Test for shorted terminals and poor connections at the affected relay. Refer to Testing for Intermittent Conditions and Poor Connections and Repairing Connector Terminals in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 16

Go to Step 14

12

Test for shorted terminals and poor connections at the engine control module (ECM). Refer to Testing for Intermittent Conditions and Poor Connections and Repairing Connector Terminals in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 16

Go to Step 15

13

Repair an open or high resistance in the battery positive voltage circuit of the affected relay coil. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 16

--

14

Replace the affected relay. Refer to Relay Replacement in Wiring Systems.

Did you complete the replacement?

--

Go to Step 16

--

15

Replace the ECM. Refer to Engine Control Module Replacement in Engine Controls - 2.5L.

Did you complete the replacement?

--

Go to Step 16

--

16
  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

--

Go to Step 2

Go to Step 17

17

Observe the Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List in Engine Controls - 2.5L

System OK