jlglr4
Full Access Member
After three years of no eco stop, no warning light bliss, my light finally turned on. Battery is shot - 10.6v - pretty sure that’s what caused the light. So now I’m trying to get a good understanding of how the Gateway Module and Power Supply Distribution Module (PSDM) works, and looking for a little help. I did read through @Michael Gain ’s helpful post on the traxide system, but I’m still looking for some clarity on a couple of points. Hopefully some of you are better at reading circuits than I am.
Attached is the circuit diagram for the starting system. On the PSDM, there are two battery terminals (Battery 1 and 2), one Load terminal, ground, and then VBatt2, FET diagnostics/Bsense, and LIN. I understand that the LIN is a comm terminal that turns the two mosfets on/off to switch the load between Batt 1 and Batt 2. I’m confused on the FET diagnostics and VBatt2 terminals.
I removed my aux battery, and when my engine is off, I have battery voltage at all three of Batt1, Batt2, and Load terminals. So, with key off, the mosfets must be connecting both Batt1 and Batt2 to the load - that’s the only way I see that I’d have 12v at Batt2. When I turn the key on/engine off or key on/engine on, I have battery voltage only at Batt1 and Load, so the mosfets are isolating the second battery with key on.
I originally thought VBatt2 must be powering the gateway module and FET diagnostics/Bsense was sensing Battery 2 health. But looking at the circuit, the gateway module would have no power with the second battery removed and the ignition on (battery 2 isolated). So, maybe VBatt2 is the sensing circuit and FET diagnostics is something else. But how, then, is power delivered to the gateway module - over the LIN circuits? Can they provide power and comm?
My second question is - how does it charge the second battery? I assume it just switches the mosfets to connect Batt2 to the load when the alternator is running, but not sure.
I find it strange that the car connects the second battery to the main battery/loads when the car is off. Seems like a bad second battery would bring down the main battery. But, I also suspect my PSDS might be faulty, and part of this excercise is trying to figure what might be wrong with it.
Attached is the circuit diagram for the starting system. On the PSDM, there are two battery terminals (Battery 1 and 2), one Load terminal, ground, and then VBatt2, FET diagnostics/Bsense, and LIN. I understand that the LIN is a comm terminal that turns the two mosfets on/off to switch the load between Batt 1 and Batt 2. I’m confused on the FET diagnostics and VBatt2 terminals.
I removed my aux battery, and when my engine is off, I have battery voltage at all three of Batt1, Batt2, and Load terminals. So, with key off, the mosfets must be connecting both Batt1 and Batt2 to the load - that’s the only way I see that I’d have 12v at Batt2. When I turn the key on/engine off or key on/engine on, I have battery voltage only at Batt1 and Load, so the mosfets are isolating the second battery with key on.
I originally thought VBatt2 must be powering the gateway module and FET diagnostics/Bsense was sensing Battery 2 health. But looking at the circuit, the gateway module would have no power with the second battery removed and the ignition on (battery 2 isolated). So, maybe VBatt2 is the sensing circuit and FET diagnostics is something else. But how, then, is power delivered to the gateway module - over the LIN circuits? Can they provide power and comm?
My second question is - how does it charge the second battery? I assume it just switches the mosfets to connect Batt2 to the load when the alternator is running, but not sure.
I find it strange that the car connects the second battery to the main battery/loads when the car is off. Seems like a bad second battery would bring down the main battery. But, I also suspect my PSDS might be faulty, and part of this excercise is trying to figure what might be wrong with it.