Last week after replacing the bulbs in my cluster panel for illumination a few days later my volt meter was low. i pulled into a parts house thinking my alternator was dying. The battery tested bad. i replaced battery and voltmeter still is staying on very low side barely moving. The truck hasn't had any starting problems. it seemed like idle was surging up and down. Only check engine light i'm aware of is for the o2 sensors.

 

All I can think of provided the alternator really is good would be bad ground on your volt meter or bad volt meter.

 

Your into 3 different responses from the observation and response you see.
1. Replacing the battery rebooted the computer so it has to relearn the drive cycles.
2. You did not check the charge system properly.
The dash meter is driven from the dash micro processor 'not' direct from the battery.
First check with a real voltmeter across the battery to see what is happening and act from the results. After starting you should see near 15 volts tapering off as the battery recharges to about 14.2 +/- no matter what the dash meter tells you.
3. If the real test shows no trouble then there is a dash issue.
4. Repair for the code you have and clean up the system.
If you get more than one trouble at a time you can't tell unless you use a Scanner to see them.
Good luck.

 

I had parts house do a check machine said bad battery. I replaced battery and idiot gauge still shows low. I checked with a multimeter and running and dvmm shows 14 or better. I bought a digital voltmeter for cigarette lighter today and 14.2 to 14.4 is the normal reading while driving. I believe it to be a gauge issue after I changed the illum. bulbs in cluster.