You are getting a low voltage reading to one of the sensors....could be a shorted sensor causing the problem...or a bad signal from the pcm....try unplugging the sensors one at a time and check the voltage and see if it comes up when you unplug one...if it comes back up when you unplug a sensor that sensor may be bad....my guess would be start with the crank sensor first....I would bet it is bad....just guessing....Jim
So you received this code P1496 but never measured the 5 V supply. Typically a single voltage regulator like the 7805 series integrated circuit is used to power everything including all the sensors and the ECM itself including the microcontroller and all the sensors it monitors.
Its fairly indestructible with foldback current limiting and thermal shutdown, but also can have poor soldering to the PCB. Code was set when its voltage dropped below 4 volts four over 4 seconds. Is your vehicle still running? If it is, you have some sort of intermittent problem and since its feeding a relatively large parallel circuit the problem can be anywhere, not only in all the sensors but within the ECM itself.
And could be an overload condition pulling the output voltage down or even a resistive connection due to a dirty connector, poor soldering joint that would give the same identical effect, low voltage. Or the supply voltage due to corrosive fuses or a dirty ignition switch.
I usually find problems in the ECM itself, wave soldered, and the larger components like the connector or this large transistor never seem to get soldered correctly so check that first. Or in the wiring harness itself if any where near heat. Could be bonding two wires together causing an intermittent short. No easy answer.