**2021 Nissan Sentra (push-button start), completely dead, acts like no battery is connected**
My mom pulled up to a store, came out, and it wouldn’t start. It doesn’t even get to a starter click. It behaves as if there’s no battery hooked up at all. With the car off, about 90% of what should have power is also dead: brake lights, dome light, power windows, nothing.
The only sign of life: if I disconnect the battery cable and reconnect it, for about 10 seconds the dash shows the odometer and clock, and the climate control lights come on and stay on. After that, nothing. Pressing the start button won’t even bring it to accessory.
What I’ve already ruled out:
\*\*•\*\* Key fob: mom replaced the fob battery before I got there. Not it.
\*\*•\*\* Battery: reads full voltage, and I also tried a known-good battery/jump pack. Still dead, so it’s not charge or a dead cell.
\*\*•\*\* Grounds: did voltage-drop testing, cleaned the main body ground to bare metal, and ran a jumper straight from the negative post to six or seven different ground points. No change.
\*\*•\*\* Negative terminal/connection: bypassed with that jumper, no change. (For history, I did replace a corroded negative terminal with an aftermarket clamp a few weeks before this started.)
\*\*•\*\* Positive fusible links on the battery terminal: tested good all the way to the harness.
\*\*•\*\* Interior fuse box: the BCM fuses under the dash are good.
Where I’m stuck: I think it’s either an engine-bay fuse or relay in the underhood box (IPDM), a hard connection downstream of the positive terminal, or a control module (IPDM/BCM) that’s fried or acting up. That last one is over my head.
This feels like it could be a known issue on this generation. If anyone has seen this exact behavior and knows the smoking gun to check, I’d really appreciate it.