In the past, a quick test for GP's was to take a test light, clamp one side to battery positive and touch the other side to the tip; if the test light lit you had continunity= good PG. If one was suspect, pull it out and bench test to directly on a battery. A couple of weeks ago with the deep cold we had I cycled my key a couple of times to help the engine start. Soon after my MIL came on and so I checked each GP as usual and found all of them tested okay with the test light; so i figured it was the buss bar. I replaced the buss bar, but a couple of days later, MIL came on again. So yesterday I went and checked them with an ohm meter. 3 were less than 1 ohm, one was 166 ohms. Took it out and bench tested and it lit up. I replaced it and now no more MIL. I even used a test light with a neon bulb which supposed to not light up brightly with a higher resistance in the circuit. Lesson learned