Originally Posted by Frango100
I would say that it is too early to come to the conclusion that the PCM is faulty.
I won't expect a ground issue, since it was running fine before the vacation.
You mentioned the erratic speedometer and the low voltage indication. Do you have the SKIM light on on the instrument panel? (the key symbol with a line through it)?
Try first the keydance and see if any fault pops up (ignition switch off/run three times and leave in run at the third time. The odometer will show DONE when all ok, or a fault code.
You said you removed the PCM connector, but the PCM has three large connectors. Are you sure you took the PCM, and not the TCM, which only has one large connector and is just in front of the PCM?
I'd suspect whatever it is that controls the alternator if the voltage is truly that low.
I suggest picking up a small digital voltmeter somewhere. Radio Shack has a small one that comes with leads and a built in carrying case for a few bucks.
First, turn everything off, and measure voltage right at the battery posts.
If that's low, your battery could be flaking out, but I'd still suspect the charging ckt, so before you spring for a new one, borrow or pick up a charger and charge the battery. You should then see about 13.2 volts or a tad higher.
If the battery with everything off is about 12.7 volts, turn on the headlights and wait 2-3 minutes and check again... this indicates a failing battery that cannot hold a deep charge--called skin effect charge.
If all is good so far, start it up and see how the battery voltage matches the displayed voltage. They should be extremely close.
If you have a set of heavy jumpers, you can try jumping from the battery NEGATIVE terminal right to the body and see what happens to the display.
Or you can jump from that same terminal to the engine block.
Or, from the block to the body.
If you have something loose, one of those should bump the voltage to normal.
Seeing bad alternator control is a bit trickier, but at very low idle, hopefully you'll see a lower voltage as measured right across the battery terminals. Then, as rpm increases, you should go to in the range of 14 volts or just a bit above.
You can also put one lead of the voltmeter on the battery ground and another on the body and you should not see more than about 0.1 to 0.2 volts across whatever grounding cable you have. Same applies to measuring from battery ground to engine block.
You can also check from the battery positive post to your starter solenoid, again, no more than .1 to .2 even when cranking.
When doing any voltage check, don't touch the battery terminals, just the posts, as the terminals could have crud betwixt them and the post.
It might be worth trying an alternator or battery shop, they could make all these measurements in a couple minutes.