Pimpinpete

2000 Silverado recently did the pcm upgrade to a 411pcm with an 02 Tahoe OS for flex and 2 bar capabilities. We've been able to get the tune all dialed in, except for stable charging rates. I had read that the Tahoe uses a 2 wire alternator connector, and the 2000 Silverado has a one wire, so you need to add a wire from terminal L on the alternator to red pin 56 on the pcm. I tried this and when slightly accelerating I would lose voltage, but it would charge at idle. Changed it back to a one wire and turned off terminal L and F dtcs in the tune, same issue, it will only give 14 volts at idle. I'm sure it's an easy fix, just can't figure it out. any tips or solutions would be great!

00pooterSS

iTrader: (40)

I'm not the most familiar with which PCM numbers mean what but an 02 tahoe should have had a 4 pin alternator connector with only the L terminal wired up to the PCM.

Then there were 2 wire alternators starting in 05 and they also used an amperage sensor on the battery cable that the PCM used to PWM the alternator fielding. If you ran the extra wire for the 2 wire it's safe to assume it's out of whack because you aren't using the amperage/current sensor.

Pimpinpete

The alternator is a four pin connector, but for the 02 Tahoe I was under the impression it utilizes the L and F terminal of the four pin connector. The original wiring for the 2000 Silverado is a four pin alternator, that utilizes terminal L of the four pin plug. Currently I have it back to one wire going into terminal L of the four pin connector, and it still won't charge under an engine load.

00pooterSS

iTrader: (40)

I wish I knew more about tuning certain PCM's to be able to help. I'm a tech and I've only ever seen one wire going to the 4 pin alternators. I've gone through a lot of alternator issues etc with F bodies and the trucks outside of what I do for a living. The earliest I know of that 2 pin alternators came on is 05 in the trucks. So if your PCM is from an 02 truck I can't see it being for a 2 pin.

Have you tried another alternator to make sure it's not an alternator issue?

00pooterSS

iTrader: (40)

I actually have a 50 page thread on alternators on LS1tech because I had about 10 alternators fail in a year and finally figured out it was just **** alternators. Once I posted up about it tons of other people were having the same problem. I went to using used alternators from the junk yard so that I could get OEM alternators. Never had a problem again after than. If you happen to have a new alternator from the parts store, don't trust it just because it's new. Make sure you're using a known good alternator.

Pimpinpete

Alternator is brand new, but I will check to see if that is an issue. The truck originally used one wire of the four in the connector, I was just told that the 02 Tahoe uses two of them.

RedXray

With my 2000 GMC Sierra V6 to V8 swap I used the 0411 ECM with a 2002 Tahoe engine wiring harness. I'm using the original 2000 four plug one wire alternator with no issues. In HP Tuners go to System > General > System Options... then make sure only the L terminal is activated.

arthursc2

iTrader: (5)

00pooterSS

iTrader: (40)

All of my alternator problems started with "brand new" alternators.

Check out my alternator thread if you want to know more about mine and tons of other peoples problems with new alternators.

If you have a 4 pin alternator. Only the L terminal should be wired.

Whoever told you the 02 was a 2 wire was wrong.

If you want to check out the alternator thread https://ls1tech.com/forums/generatio...failure-s.html

Pimpinpete

Alright, thank you for the responses. I have been a bit busy with work the past few days, but hopefully I'll have time this week to check it out. I'll post on the results once I figure it out.