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2005 Chevrolet Tahoe 5.3L P0480: Cooling Fan Runs After Engine Off - Diagnosis & Fix

Model: 2005 Chevy Tahoe 5.3L Fault Code: P0480 Posted: 2017-01-11 18:56

I'm new here, so please be patient with me. I've noticed that approximately two hours after turning off my engine, the cooling fan starts running at a low speed—even when the key is out of the ignition. This behavior is not normal and has been happening for some time. I had the vehicle scanned, and the only fault code detected is P0480—though the symptoms seem different from what I've seen in other posts. I’ve already replaced the cooling fan relay (Relay #1), which is located either in the main fuse box or a separate relay box under the hood near the radiator. However, after replacing it, the issue returned and my battery drained overnight. I’m now wondering if the problem lies with another relay or deeper wiring issues. I’ve also observed that during startup, the engine idles unevenly—revving up and down for about 20 seconds. The vehicle has been driven for over 8 years with around 170,000 miles. We've never cleaned the engine compartment, and all major components—including water pumps, headlamp relay, belts, hoses, and pulleys—have been replaced recently. The only other codes I recall were related to knock sensors; I may need to re-scan for additional faults. I appreciate any insights or troubleshooting steps that could help resolve this issue.

Related fault codes
P0480
Comments (11)
Anonymous 2017-01-12 08:11

Try replacing the cooling fan relay #1—first, check if it's located in the main fuse box or a separate relay compartment under the hood. This area is typically just rearward of the main fuse box and holds multiple fan relays and fuses.

Anonymous 2017-01-12 08:55

Thanks for the help! I'll update you once I get back home with results after trying the relay replacement.

Anonymous 2017-01-16 08:18

I replaced Relay #1, and initially thought it fixed the issue. However, this morning the fan started running again, and my battery was completely drained. Could replacing the other two relays in the system make a difference? I'm not sure if there's a circuit overload or grounding issue.

Anonymous 2017-01-16 09:19

If your only code is still P0480, you'll need to inspect the wiring, circuit paths, and components—especially why two relays have failed. Start by measuring the amp draw of the fan motors; a high current draw can cause relay contacts to overheat or fuse. While I don’t have the system diagram on hand right now, I’ll try to locate it and share it later.

Anonymous 2017-01-16 09:36

I’ve noticed that the engine idle is unstable—it revs up and down during startup for about 20 seconds. The Tahoe has been driven for over eight years with 170,000 miles. The engine bay looks clean and well-maintained, but we've never performed a full cleaning. We've replaced water pumps, headlamp relay, two sets of belts, all hoses, idler pulleys, and tensioners. The only other codes I recall were knock sensor-related; I’ll need to re-scan for any additional faults. Thanks for your time and insight!

Anonymous 2017-01-18 11:17

The issue was resolved! There’s a box located just under the battery, near the radiator. It has two connectors with many wires secured by a 6mm bolt. After removing it, I found that one plug was wet and had severe corrosion on the bottom male pins. The male side has a blue cover over the pins. I removed this cover to access the pins better. Upon inspection, one pin appeared to have growth touching the metal casing—likely causing a short circuit. I cleaned all pins with contact cleaner, used a small wire brush, dried them thoroughly, and applied electric grease. Note: The gasket should be installed on the male plug side.

Anonymous 2018-06-15 21:29

Thanks for sharing this! This exactly matches what happened in my father’s truck. After cleaning the corroded pins, the fan stopped running after shutdown. I’m very grateful for your post!

Anonymous 2018-06-15 21:36

You're welcome—happy to help!

Anonymous 2018-11-30 09:29

The blue connector on the PCM module was causing P0480. After unplugging it, a large amount of water came out. I blew out the moisture and applied dielectric compound before reconnecting. Now, the fan stops after engine shutdown, and there’s no more battery drain in the morning. I hope this also resolves unrelated intermittent codes like 171 and 172—those were likely caused by water intrusion affecting about ten pins on the connector.

Anonymous 2021-02-06 12:55

This is a life-saver! There aren’t many YouTube videos covering this issue. It took me some time to figure out how to disconnect the wires—on my model, the bolt behind the connector is 7mm, not 6mm. I found the same problem: severe corrosion at the bottom of several pins on the blue plug. After cleaning and applying dielectric grease, the fan stopped running after shutdown. Thanks a million!

Anonymous 2021-05-20 00:14

A friend recently bought a 2005 Chevrolet Tahoe 5.3 with the same issue—the cooling fan runs after engine shutdown. After going through the full diagnostic process, I pulled the PCM connector and found massive corrosion on several pins at the bottom of the blue-side plug. One male pin had actually come loose and was stuck in the female socket. While there’s a lot of information about circuit diagnostics, posts like this one—and videos on YouTube—are rare. This seems to be a common issue with older 5.3L engines. Chevrolet should consider addressing this through a recall! Thanks for sharing—#Clovern