No aftermarket electronics of any kind installed on/in your truck?
it only does it "while truck is in neutral or a gear with the brake not applied"?
What happens if you apply the brake or speed up while it is doing this?
does it start doing it when you are going 40mph or any speed?
it only does it "while truck is in neutral or a gear with the brake not applied"?
What happens if you apply the brake or speed up while it is doing this?
does it start doing it when you are going 40mph or any speed?