I'd recommend replacing it. As was previously stated, don't power the head unit up without it. I'm not 100% sure that it's a problem but, from the values in the head unit. the voltage should be greater than 4v. The current voltage 'may' be enough. I don't know because the MCU doesn't give threshold voltages. Unless someone has experience with these, getting the voltage up to about 5v is the next thing to do.
You can't use your multimeter on ohms or diode-check with power applied and even having the part in the circuit can skew readings.
When on ohms or diode-check, the meter drives a small voltage to the probes and the difference in the loaded/unloaded probe voltages tells the meter what to display. Having voltage on the circuit changes the voltage across the probes and therefore the reading.
When on ohms or diode-check, the meter drives a small voltage to the probes and the difference in the loaded/unloaded probe voltages tells the meter what to display. Having voltage on the circuit changes the voltage across the probes and therefore the reading.