I dont think a low O2 sensor voltage would cause a no start issue unless a wire melted and crossed with a ground or even crossed another power to hurt the engine computers...
This pressure you speak of is it fuel pressure? If so, find the fuel pump power and ground wires. Check for power and or ground. If you have power for a short time usually less than 5 seconds after turning key to ON position then everything before this pigtail is good. If not......create a known good ground and power and apply them to the wires only after disconnecting the main pigtail or harness to the fuel pump so that the pump is off the vehicles system. Pump should go on if there is a relay,wire,fuse,ignition,battery connection or anything other than a bad pump. This is the fastest way to verify a bad pump. Guessing gets expensive. (dont quote me, but usually large grey and large black wire in the 4 pin are the two wires. grey i think may be power, blk may be ground) double check with a real diagram. If you have a volt meter, well you can check for your self much easier. 15 dollar tool at a harbor frieght
Good luck
DTC P0157 HO2S Circuit Low Voltage Bank 2 Sensor 2
Check for the following:
HO2S wire - Sensor pigtail may be mispositioned and contacting the exhaust manifold
Intermittent ground in the wire between the connector and the sensor
Poor VCM to engine block ground
Lean injector(s). Perform Fuel Injector Balance Test for the 5.7L or the 7.4L.
Fuel contamination. Water, even in small amounts, near the in-tank fuel pump inlet can be delivered to the injectors. The water causes a lean exhaust and can set a DTC P0151
Fuel pressure. System will be lean if pressure is too low. It may be necessary to monitor fuel pressure while driving the vehicle at various road speeds and/or loads to confirm. Refer to Fuel System Diagnosis.
Exhaust leaks. If there is an exhaust leak, the engine can cause outside air to be pulled into the exhaust and past the sensor.
Vacuum or crankcase leaks can cause a lean condition and/or possibly a high idle.
If the above are OK, it is a faulty HO2S.
Never solder the HO2S wires.
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