Has anyone on here ever encountered the P0480 code, and found the cause of it? Thanks in advance for any help...

 

DTC P0480
Circuit Description
Battery positive voltage is supplied to the coolfan 1 relay from the coolfan 1 fuse. The powertrain control module (PCM) controls the coolfan 1 relay by grounding the low speed coolfan relay control circuit through an internal solid state device called a driver. The primary function of the driver is to supply the ground for the component being controlled. Each driver has a fault line which is monitored by the PCM. When the PCM is commanding a component on, the voltage potential of the control circuit should be low, near 0 volts. When the PCM is commanding the control circuit to a component off, the voltage potential of the circuit should be high, near battery voltage. If the fault detection circuit senses a voltage other than what is expected, the DTC will set.

 

Good info, thank you. I am having PCM rebuilt right now hoping it is at fault since I have already checked fuses, relays, fan motor, grounds, and wiring.

 

Put supposedly rebuilt PCM back in, and have same code and issue! I'm at my wits end with this car. I guess I will take it to dealer...

 

heres the entire procedure for it;

DTC P0480 Cooling Fan Relay 1 Control Circuit
Refer to Cell 20: Engine Cooling Fans for complete circuit details.

Circuit Description
The cooling fan system in this vehicle provides for two separate modes of operation. These are the low speed fan and the high speed fan operating modes. The low speed mode operates both fans at half speed by using a series circuit configuration. The high speed mode operates both fans at full speed by using a parallel circuit configuration. These two operating modes are accomplished using 3 fan control relays.

This system which uses three relays to control two fan motors appears complicated. To aid in better understanding this system it is suggested to follow the circuits in the schematic as you read the description. This aids in understanding the two distinct modes of operating the relays and coolant fans.

The low speed fan operation is established when the PCM commands Fan Relay #1 ON by grounding circuit 335 with an internal driver (relays #2 and #3 are left OFF). This closes the relay switch and allows current to flow from the battery, through the switch contacts on circuit 409 to the Left Hand (LH) cooling fan. Current flow continues out of the fan motor on circuit 532 to relay #3. The un-energized relay #3 switch contacts allow current to flow to circuit 504. This provides power to the Right Hand (RH) cooling fan motor. The low side of the RH cooling fan completes the circuit to ground on circuit 250. This is a series circuit which allows half speed operation for each fan since each fan motor uses half of the supplied battery power.

The high speed operation is established when all three relays are energized. Relays #2 and #3 share the same control circuit to the PCM. This is circuit 473. As in the low speed mode, Relay #1 supplies current flow to the LH cooling fan on circuit 409. Current flow continues through the motor on circuit 532 to relay #3 which is now energized. The switch has now provided a path for current to flow through circuit 250 directly to ground. This circuit now only has the LH fan motor to power and allows it to run at full speed. Relay #2 is also energized and provides current flow on circuit 504 to the RH cooling fan. This fan now has its own dedicated circuit and will operate at full speed. This mode is operating as a parallel circuit.

Conditions for Running the DTC
The engine speed is greater than 400 RPM.
The system voltage is between 6 volts and 18 volts.
Conditions for Setting the DTC
The PCM detects that the commanded state of the driver and the actual state of the control circuit do not match.
All of the above conditions present for a minimum of 5.0 seconds.
Action Taken When the DTC Sets
The PCM illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the PCM stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the PCM records the operating conditions at the time of the failure. The PCM writes the conditions to the Freeze Frame and updates the Failure Records.
Conditions for Clearing the MIL/DTC
The PCM turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A last test failed, or current DTC, clears when the diagnostic runs and does not fail.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Use a scan tool in order to clear the MIL and the DTC.
Diagnostic Aids

Important
Remove any debris from the PCM\TAC module connector surfaces before servicing the PCM\TAC module. Inspect the PCM\TAC module connector gaskets when diagnosing/replacing the modules. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion into the PCM\TAC modules.
For any test that requires probing the PCM or a component harness connector, use the Connector Test Adapter Kit J 35616-A . Using this kit prevents damage to the harness/component terminals. Refer to Using Connector Test Adapters in Wiring Systems.

The following may cause an intermittent:
Poor connections; Refer to Intermittents and Poor Connections Diagnosis in Wiring Systems.
Mis-routed harness.
Rubbed through wire insulation.
Broken wire inside the insulation.
Using Freeze Frame and/or Failure Records data may aid in locating an intermittent condition. If you cannot duplicate the DTC, the information included in the Freeze Frame and/or Failure Records data can aid in determining how many miles since the DTC set. The Fail Counter and Pass Counter can also aid determining how many ignition cycles the diagnostic reported a pass and/or a fail. Operate the vehicle within the same freeze frame conditions (RPM, load, vehicle speed, temperature etc.) that you observed. This isolates when the DTC failed.
For an intermittent, refer to Symptoms .
Cooling Fan Relay #1 Underhood Electrical Center Terminal Identification

Front of Vehicle

Driver Side of Vehicle
Control
B+
Passenger Side of Vehicle

Load
B+


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

Listen for an audible click when the relay operates. Command both the ON and the OFF states. Repeat the commands as necessary.

This test can detect a partially shorted coil which would cause excessive current flow. Leaving the circuit energized for 2 minutes allows the coil to warm up. When warm the coil may open (amps drop to 0), or short (goes above 0.75 amp).

Identify and test the relay coil terminals in order to avoid improper diagnosis.

Listen for an audible click when the relay operates. Repeat the procedure as necessary.

If you do not find any trouble in the control circuit or the connection at the PCM, the PCM may be faulty. However, this is an extremely unlikely failure.

Step
Action
Value(s)
Yes
No

1
Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?
--
Go to Step 2
Go to Powertrain On Board Diagnostic (OBD) System Check

2
Turn ON the ignition leaving the engine OFF.
Command the relay ON and OFF using a scan tool.
Does the relay turn ON and OFF when commanded?
--
Go to Step 3
Go to Step 5

3
Turn OFF the ignition.
Disconnect the PCM connector C1 located on the same side as the manufacturer's logo. Refer to PCM/TAC Module Replacement .
Turn ON the ignition.
Measure current from the relay control circuit in the PCM harness connector to ground for 2 minutes using DMM J 39200 on 40 amp scale.

Important
Replace the relay if the DMM goes to 0 during the current draw test.


Does the current draw measure less than the specified value?
0.75A
Go to Diagnostic Aids
Go to Step 4

4
Turn OFF the ignition.
Disconnect the relay.
Measure the resistance from the relay control circuit in the PCM harness connector to ground using the DMM J 39200 . Refer to Testing for Continuity in Wiring Systems.
Does the DMM display infinite resistance?
--
Go to Step 12
Go to Step 10

5
Turn OFF the ignition.
Disconnect the relay.
Connect the test lamp J 34142-B between the FC relay 1 control circuit and the FC relay 1 B+ supply circuit at the underhood electrical center. Refer to Diagnostic Aids for terminal identification.
Turn ON the ignition.
Command the relay ON and OFF using a scan tool.
Does the test lamp turn ON and OFF with each command?
--
Go to Step 8
Go to Step 6

6
Probe the FC relay 1 B+ supply circuits at the underhood electrical center with the test lamp J 34142-B connected to ground.

Is the test lamp illuminated?
--
Go to Step 7
Go to Step 11

7
Turn OFF the ignition.
Reconnect the relay.
Disconnect the PCM connector C1 located on the same side as the manufacturer's logo. Refer to PCM/TAC Module Replacement .
Turn ON the ignition leaving the engine OFF.
Momentarily probe the relay control circuit in the PCM harness connector with a fused jumper wire connected to ground. Refer to Probing Electrical Connectors and Using Fused Jumper Wires in Wiring Systems.
Does the relay turn ON when the control circuit is grounded and turn OFF when the control circuit is opened?
--
Go to Step 9
Go to Step 10

8
Inspect for poor connections at the relay. Refer to Intermittents and Poor Connections Diagnosis in Wiring Systems.
If you find a poor connection, repair as necessary. Refer to Repairing Connector Terminals in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 14
Go to Step 12

9
Inspect for poor connections at the PCM. Refer to Intermittents and Poor Connections Diagnosis in Wiring Systems.
If you find a poor connection, repair as necessary. Refer to Repairing Connector Terminals in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 14
Go to Step 13

10
Repair the relay control circuit. Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?
--
Go to Step 14
--

11
Repair the relay B+ supply circuit. Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?
--
Go to Step 14
--

12
Replace the relay.

Is the replacement complete?
--
Go to Step 14
--

13

Important:
Program the replacement PCM. Refer to PCM/TAC Module Replacement .


Replace the PCM.

Is the action complete?
--
Go to Step 14
--

14
Select the Diagnostic Trouble Code (DTC) option and the Clear DTC option using the scan tool.
Start engine and idle at normal operating temperature.
Select the Diagnostic Trouble Code (DTC) option and the Specific DTC option, then enter the DTC number using the scan tool.
Operate vehicle within the Conditions for Running this DTC as specified in the supporting text, if applicable.
Does the scan tool indicate that this test failed?
--
Go to Step 2
Go to Step 15

15
Select the Capture Info option and the Review Info option using the scan tool.

Does the scan tool display any DTCs that you have not diagnosed?
--
Go to the applicable DTC table
System OK



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Thanks for chiming in Bill. The shop that rebuilt my PCM said it did have a burned up board that controls the fan 1. I still have same code and symptoms. They are going to swap me out for another PCM. How do I do the relearn procedure? Thank you.

 

I gave up, and took it to Chevy dealer...

 

Where did you have the pcm repaired at? and please keep us posted as I have done the same checks as you, relay and fuses. I by passed the relays and fans came on no prob. how ever from the scan tool I could not command the fans to come on. I hope mine is just a pcm but I am curious what the dealer finds on yours.