TobyZ28

What should the PCM in freescan read for voltage at Idle and when running? My car at idle is low 12V and at 3000 RPM on the highway is around 12.8 at the most. These readings were taken from freescan. If I have the Power inverter plugged in for my laptop and the AC on i've seen the voltage drop to 11.6 ish.

Is the voltage reported by the PCM gernally very accurate? Is it a sensor i can test and /or replace? Do I need a new alternator?

shoebox

There is no sensor. It just reads voltage incoming to the PCM, itself. Sometimes diagnostics can report the voltage a little low for some reason. Compare the reading to a digital meter connected at the battery to check for accuracy.

RobbyRob

I'm changing my alternator. Mine shows it dropping off down 10 & 11 volts. Not good for making power. Powermaster alternator has sent me part #'s for my Z.
Here are the part #. 17805 chrome 140 amp,
27805 chrome, natural, black 200 amp

TobyZ28

Well i had the voltmeter up against the battery and it was pretty solid above 14 volts with highbeams, AC on high while idling.... Seems like freescan (or perhaps the pcm) is steadly off by 1.5 volts.... Thnx shoebox

RobbyRob

Mine has shown drops in voltage off the alt and batt. When a/c lights or fog lights. Not just 1 volt.