It's connected to a eS656 (not that that matters much). I've had several sensor related problems lately with the Sharp "73" sensors, so I'm well in practice with diagnosing them. The symptoms don't make any sense though.
Initially, I put my meter on the sensor pins (entrance sensor PI1). The meter readings weren't even close to what they should be ... so it took a few minutes to determine if I was pinning it out correctly. The ground is present, the 5vdc supply voltage is 0.859vdc steady, and the PENT signal voltage is 1.25vdc steady, no change blocked or unblocked.
I have 6 of the Sharp "73"s in my car, so I tried each of them, no change. The sensor never changes state, supply voltage always low. Then I falsely concluded that the finisher controller board was bad. A few days later, I installed the controller and ran the adjustments. Yes, it's not the controller.
Next I pinned out the 16" of harness. Not a lot of harness. No shorts or opens. Here's the interesting part: When I unplug PI1, the supply voltage comes back to 5.01vdc. When you unplug any of the sensors the supply voltage comes back to 5.01vdc. I can take it a step further. I tracked the 5v back to a trace on the surface of the finisher controller. The only thing between J17-7 (PI1 supply voltage) and the surface trace is resistor R158. The surface trace remains at 5.01vdc. The other side of R158, J17-7 drops out to 0.859vdc. And the signal PENT never changes state from 1.25vdc. All the sensors respond this way.
Does this logically lead you to any conclusions? I'm still puzzled. =^..^=
Initially, I put my meter on the sensor pins (entrance sensor PI1). The meter readings weren't even close to what they should be ... so it took a few minutes to determine if I was pinning it out correctly. The ground is present, the 5vdc supply voltage is 0.859vdc steady, and the PENT signal voltage is 1.25vdc steady, no change blocked or unblocked.
I have 6 of the Sharp "73"s in my car, so I tried each of them, no change. The sensor never changes state, supply voltage always low. Then I falsely concluded that the finisher controller board was bad. A few days later, I installed the controller and ran the adjustments. Yes, it's not the controller.
Next I pinned out the 16" of harness. Not a lot of harness. No shorts or opens. Here's the interesting part: When I unplug PI1, the supply voltage comes back to 5.01vdc. When you unplug any of the sensors the supply voltage comes back to 5.01vdc. I can take it a step further. I tracked the 5v back to a trace on the surface of the finisher controller. The only thing between J17-7 (PI1 supply voltage) and the surface trace is resistor R158. The surface trace remains at 5.01vdc. The other side of R158, J17-7 drops out to 0.859vdc. And the signal PENT never changes state from 1.25vdc. All the sensors respond this way.
Does this logically lead you to any conclusions? I'm still puzzled. =^..^=