not sure which forum to put this in..but, i bought a wrecked 99 silverado with a 5.3. i've got the truck up and running with the 6.0 out of my cutlass. i'm also using the 02 truck computer from my cutlass. the alternator light stays on in the dash. the charge indicator shows 14+ volts and a voltmeter on the battery itself shows that the alternator is charging. any ideas on the light? do i need to change a pin out on the pcm? i have not changed the vin on the computer to match the bcm, is this a problem? thanks.

 

Heres your answer to your flashing light .

I will be doing the same thing also .

 

thanks! i did a search earlier but didn't find any info.

 

I didn't read the whole linked post, but I didn't see the cause described, only a solution. The 99-00 alternators were one-wire alts. If I'm not mistaken, the single wire is there to measure output voltage, and that's it. The alt is on all the time (self-regulated). The 01 and up alts were two-wires, one to measure output voltage and one to adjust the voltage regulator. When you hook a one wire alt up to a PCM that's expecting two wires, it doesn't get the second signal and trips the battery light. Alternatively, you can't take an alt out of a newer truck and put it in a 99-00 truck, cause it won't charge without the signal from the second wire.

I ran into this problem on my custom built HO alt, execpt mine was actually turning off at times. My voltage would drop from 14 to 12.5 every 10 seconds or so at idle, and any time I was under load with the headlights on. I had the regulator replaced with a self-regulating unit, which caused my light to come on all the time. I had Bryan at PCMFORLESS turn off the battery light. The code is still stored in the PCM, but the light doesn't come on anymore.

 

thanks thunder, i guess i have 2 options, wire up the second wire or turn off the light with hp tuners. the harness i used with my cutlass matched the 02 computer so i'll probably just cut the plug off and wire it back into the 99 harness. thanks for the explanation.

 

Sure, that battery light is definitely annoying! That was basically my reason for getting the tune. Expensive f***ing light.