Originally Posted by ProfessorBlaze
Alternator tested fine so it isnt alternator. Im going to try adding thicker wiring.. Is it possible thd pcm is bad but still allows the car to run/drive just fine? It now starts perfect too if the voltage is above 11v
It doesnt charge right most of the time to the point of needing jumped part of the time.
Battery - new means nothing, only 2 companies left in USA that make them and slap sellers name on them.
Many are made outside the USA and the date label means nothing, they could have been made 2 years ago. Common for 1 cell never is active or quickly degrades
Even the highly hyped Optima brand went belly up and was sold couple years ago I think it was Interstate brand.
Load test on a regular basis, tester is only about $50.
Do not guess, use a good OBD scanner, for the PCM there is OBD parameters that tell what the voltage is at the PCM and then as to Alt there is one line tells what the output of Alt is and the other line tells you what the PCM is commanding the Alt to output.
Find out with scanner is and when PCM is commanding Alt to produce and what percent.
Also with scanner connect to other controllers and see what the voltage readings to them are.
Possible one of the wires to/from ALT and PCM is broke or partial cut.
Voltage reading at battery posts mean nothing as there is voltage drops by the time it gets to controllers, sensors, fuel injectors. etc.
Possible in past older battery leaked acid below to PCM so get in there look for white traces of acid damage to wiring loom
Take off both 80 pin wiring connectors to PCM and with good light check make and female pins for acid or dirt and clean well.
Make sure all the male pins that none have pushed inward of PCM.
Check for clean and tight grounds, take ground spice packs apart and good cleaning
Possible the terminals of battery cables bad.
Engine running, all other electronics off the DIC should show close to mid 14 volts, anything below mid 13s then something is wrong and begins to degrade controllers working correctly.
Check fuses, check if horn works.
There is zero reason to replace with larger wires, will not fix what the real problem is.
Check that no relay is stuck closed and drawing voltage when ign key is off.
Move everything like seats, mirrors, etc to force relays to change state.
Use current/amp meter and test to see what current draw is when ign is off.
Wait good 30 minutes after doors are shut and time for controllers to go to sleep before judging current draw.