So the service manual doesn't say much. They have a kind of cryptic diagram of how to test the wiper amplifier with a test lamp on page EL-95. I suppose you could try that. I'm unclear if you're grounding pins 1,3,and 6 all at the same time, or moving the ground around. If I'm reading it correctly, the light should be connected through pins 2 and 4, and when grounding pins 1, and 3, it should not light up - but grounding pin 6 should cause the light to come on.
You can check out the service manual at
www.infinitiservicemanual.com