Electrical System Issues:
* Alternator Failure: A completely dead alternator won't charge the battery. Once the battery is drained, everything shuts down. This is a very common cause of this type of failure.
* Battery Failure: A completely dead or severely weak battery can also cause a complete loss of power. Test the battery's voltage and cranking amperage.
* Fuses and Relays: A blown fuse or failed relay in a critical circuit (like the main power distribution) could cut power to everything. Check all fuses, paying close attention to the larger ones.
* Wiring Harness Damage: A damaged or corroded wire in the main power harness can interrupt power flow. Look for any signs of damage, especially near the battery and engine. Rodents can be culprits here.
* Ignition Switch Problem: A faulty ignition switch might not be sending power even when the key is turned.
* Starter Motor: While a faulty starter *prevents* starting, sometimes a severely failing starter can also draw excessive current and lead to a sudden power loss.
* ECU (Engine Control Unit) Failure: A complete ECU failure would shut down all engine functions and potentially other systems controlled by the ECU. This is less likely but possible.
Fuel System Issues (Beyond the Fuel Pump Sensor):
* Fuel Filter Clog: A severely clogged fuel filter can starve the engine of fuel, causing a sudden stall. This is less likely to cause a complete electrical shutdown, but it's possible if the fuel pump is also being overworked.
* Fuel Pump Relay: Even with a new sensor, a faulty fuel pump relay might not be supplying power to the pump.
Other Possibilities:
* Immobiliser System: If your vehicle has an immobiliser system, a problem with the transponder chip in your key, the immobiliser module, or the wiring could prevent the engine from starting and cause the complete loss of power.
Troubleshooting Steps:
1. Battery Voltage Test: This is the most crucial first step. Check the battery voltage with a multimeter. A low voltage indicates a charging system problem or a dead battery.
2. Check All Fuses and Relays: Systematically check all fuses and relays, replacing any that are blown.
3. Visual Inspection of Wiring: Look for any signs of damage, corrosion, or rodent chewing in the main wiring harness.
4. Alternator Test: Test the alternator's output voltage while the engine is running (if you can get it running briefly).
5. Fuel Pressure Test: If you suspect a fuel system issue, test the fuel pressure at the fuel rail.
6. Have the Vehicle Scanned: A professional mechanic can use a diagnostic scanner to read fault codes from the vehicle's computer, which can pinpoint the problem more precisely.
It's strongly recommended to have a qualified mechanic diagnose this problem. A sudden complete power loss is not something to try and fix yourself without proper tools and experience, as you could risk further damage or injury.
