I think there is a way to test a relay for power or to make sure it clicks when you engage it. They're easy to replace. I had the relay go bad on the fog light setup on my 4Runner. If your SES light goes out and comes back on it might be a loose connection at the relay or the relay getting ready to go bad.
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69 Z28 JL8 4 wheel disc brakes - being restored
09 Silverado Z71
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