What Does P0480 Code Mean?

OBD-II Code P0480 is defined as a Cooling Fan Relay 1 Control Circuit

The purpose of the electric cooling fan system is to provide extra cooling capacity to the conventional radiator cooling system on hot days, and/or when the A/C is on, and/or when the vehicle is being driven in stop and go traffic which causes insufficient air flow over the radiator. 25 years ago, most cars and light trucks utilized a mechanical cooling fan attached to the front of the engine to increase air flow through the radiator. However, as fuel economy and low emissions became a high automobile design priority, vehicle engine cooling systems incorporated computer controlled electric cooling fan systems and abandoned the less efficient mechanical cooling fan.

When code P0480 is triggered, the power train control module or PCM is commanding the cooling fan to operate, but the PCM is not seeing the proper electrical feedback from the cooling fan circuitry that would indicate the fan is operating properly.

P0480 Symptoms

  • Check Engine Light will illuminate
  • Engine may overheat and/or the Temperature Gauge may read very high 
  • Pinging/detonation on acceleration
  • Emission Test failure for high NOx 
  • Decrease in fuel economy
  • In unusual cases, there are no adverse conditions noticed by the driver
  • In some cases, there may be performance problems, such as dying when coming to a stop and/or misfire-like symptoms

Common Problems That Trigger the P0480 Code

  • Defective Cooling Fan Relay
  • Corroded Cooling Fan Relay terminals 
  • Defective Cooling Fan
  • Defective Cooling Fan wiring and/or connections
  • Problems with the Engine Cooling System 
  • Defective Coolant Temperature Sensor, its wiring/connections
  • Poor Electrical System ground(s)
  • Defective PCM, its wiring/connections
  • Large Parasitic battery drain
  • Defective Battery/Cables

Common Misdiagnoses

  • Cooling Fan
  • Radiator, Water Pump, Thermostat
  • Defective Battery
  • Defective Charging System

Polluting Gases Expelled

  • HCs (Hydrocarbons): Unburned droplets of raw fuel that smell, affect breathing, and contribute to smog
  • NOX (Oxides of Nitrogen): One of the two ingredients that, when exposed to sunlight, cause smog

P0480 Diagnostic Theory for Shops and Technician

I find it best to use a bi-directional scan tool (if possible) to inspect the operation of the cooling fan system. I like to view the commands given by the PCM (or myself) to the cooling fan relays. Then I observe the activation of the cooling fan relays while observing the operation of the cooling fan(s). I like to see a predictable engine temperature that oscillates as the cooling fans go on and off. Usually, I see the PCM activate the cooling fan(s) at around 225 degrees F and they will shut off at about 207 degrees F. This inspection is performed with the Air Conditioning off, the engine idling and the vehicle in Park on a 60+ degree F day.

Common Tests for the Electric Cooling Fan System

  • Retrieve the code and write down the freeze frame information to be used as a baseline to test and verify any diagnosis and repair.
  • Verify that the conventional cooling system works properly and does not leak.
  • Inspect the condition of the cooling fan(s), its wiring/connectors, paying very close attention to the condition of the relay(s). If you see signs of corrosion on the the relay terminals or relay box connections, replace all of the pertinent relays and clean the relay box terminals with electrical contact cleaner, Coat the new relay terminals with dielectric grease to inhibit further corrosion. 
  • It never hurts to do a current draw of the cooling fan motors.
  • If the system uses a duty cycling controller, verify that the fan motors work properly in 5-10% duty cycle increments.
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