Hi All;
I've been trying to help out with the setup of an LS swap for the last six months. I'm not a mechanic and know little about engines but been poking at computers since the early 80's, so that makes me very dangerous, LOL. Big shout out to all you guys as this site has already been very helpful in this journey.
Here's what we have to work with.
- 2007 5.3ls from a 1500 series truck (GMT800 platform)
- P59 PCM from same truck (Blue and Green connectors)
- Alternator, original to the engine when we got it has the two wire connector (L and F terminals only)
The truck originally had the separate BCM that had the current probe on the negative battery lead. We did not use that piece in our swapped setup.
We have ran the L and F alternator connections back to the PCM to terminals 15 and 75 of the green connector and also enabled the L terminal in HP Tuners under System/Options, but we can't seem to get the alternator to charge at anything other than about 13.5 volts. All the online searching we have done says that we should be able to get this setup to work and the PCM should control the voltage output of the alternator but so far we have not been able to get anything other than 13.5 volts. We have tested the alternator with a 5V PWM source and we can control the voltage so we have to assume that our alternator is working. Our backup plan is to use one of those PWM setters that people are using which at the end of the day might be a handy option to have since it can be manually set.
We believe that the P59 was used in vehicles without the BCM and it did control the alternator in the way we were expecting. We have noticed from looking at the various wiring diagrams online that in at least some of those setups the alternator used was the older 4 terminal version. (S, F, L, P connections) Is this what we are missing. Do we need to change the alternator ( OR AT LEAST THE REGULATOR) or should the P59 be able to directly control one of these two pin (F and L only) alternators?
Thanks
Jim