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B2580 trouble code GM

Diagnose and fix B2580 code on GM

The B2580 code refers to a problem with the vehicle’s lighting systems. Many GM vehicles use a high beam relay to switch on the high beam lights. However, not all systems are the same. If the vehicle has daytime running lights, GM uses the high beams at reduced power to provide the DRL function. To dim the lights, GM uses a pulsing voltage to reduce the amount of current used by the DRL. GM has had plenty of problems with this DRL system and has issued several safety RECALLS. See these

GM DRL lights don’t work

No headlights Trailblazer Envoy

What causes the B2580 code?

When you turn on your high beams or use the flash to pass function, the headlight switch doesn’t actually switch power to the high beams. It just acts as a signal to the body control module (BCM). The BCM sees the request and provides ground to the control coil inside the high beam headlight relay located in the underhood fuse box. The control coil gets power from the underhood fuse box. Once the control coil receives ground, the contacts close and power flows through the relay and on to the high beam headlights.

The BCM measures the amount of voltage present on the ground circuit. If the control coil is shorted to ground or has an internal short, the BCM will detect that and set a B2580 trouble code.

Diagnose and fix B2580 trouble code

Listen in the underhood fuse box for the relay click when

DRL relay

19116058 GM DRL relay

you turn on the headlights. That would indicate that the power to the control coil is present and the coil is energizes and moving the contacts. Then test for power at the high beam headlight socket. If the relay doesn’t click, swap it with another relay of the same size and number and see if that solves the problem. If so, replace the bad relay.

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Posted on by Rick Muscoplat

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