Another charging issue

Hi, this is my first time posting but I’ve used this forum many times to diagnose and repair the three tacomas I’ve owned over the last 20 years. My 2006 base model 2.7 is not charging the battery. I’ve done the basic check list, cleaned grounds, replaced and tested alternator, battery, voltage regulator. Ran continuity tests on battery leads and wire between alternator and b+. Voltage drop test, I even tried cussing at it. I’m going to list the voltage readings I get from the four pin connector at the alternator first with key off:from the top right when standing in front of the engine bay, the yellow wire which I believe is the terminal s, the wire that senses voltage at the battery and reports to the regulator I get 12.24, the same as I get at the battery. Moving clockwise around the connector the blue wire gets a reading that is unstable bouncing between 1.3 and 1.6 volts. The two remaining wires read zero.
With the key on, engine not running, I get 12.09 at the battery, 11.71 at the yellow (s terminal) wire, 11.8 at the blue, 10.45 at the grey( lower left) wire and 11.45 at the pink (upper left) wire. Should I be getting voltage at all four pins and should they all very? My dash doesn’t have an alternator icon that lights up with the initial key turn, I don’t remember ever seeing one, does anyone know if the 2006 has one? With the engine running the battery light stays illuminated all the time accept for yesterday when I connected a 180 amp hour lifepo4 battery in parallel so I could drive it over an hour away, ten minutes into the drive, the battery light went off and the voltage meter I have in a 12 volt socket jumped to 13.8.
It remained low and unchanged for a moment the next 3 times I started the engine then repaired itself again with the battery light turning off and the system reading 13.8 after driving for 30-45 seconds or so. But only those 3 times, it hasn’t worked correctly since then. I hope someone knows where the problem is, I’m ready for this issue to be resolved! Thanks in advance-Mike

 

I am not clear if you meant you replaced alternator with a new one.

 

Sounds like you have a bad connection or a faulty alternator.

Grab you a test light and check the terminals at the alternator plug.

https://www.tacomaworld.com/threads/2nd-gen-information-diagnostics.784008/#post-28042155

 

My diagram doesn’t show a yellow wire for the “S” terminal. So I will go off the assumption the yellow wire is the “s” terminal.
You should have battery voltage on the Pink and yellow wire, and near battery voltage on the grey wire, with key ON. The gray wire is the ground wire for the battery light. If the alternator senses low battery voltage it grounds the gray wire, illuminating the battery light.

As for the blue wire, I don’t know what it should be key off.
It goes to the ECM.

 

I forgot all about the charging system being part of that.

 

Twice. I even installed it in my friends 2007 Tacoma and it worked fine

 

Is the #2 pin the s terminal?

 

I guess my next move is to pull my dash apart and find the alternator warning bulb. Can someone with a 2006 post a picture of their dash with all the lights on?

 

#1 pin is “s”

 

I’d ground the grey wire Pin #4 before I pulled the dash apart.
If you ground the grey wire, the battery light should illuminate.
But you shouldn’t need to do that. A bad bulb would not allow voltage to that pin.

 

The battery light or the alternator light?

 

The battery light is the alternator light.
There isn’t a separate light. The battery light is for the alternator.
I don’t know why Toyota uses a battery symbol, it would be better suited if it were a “charge” light.

 

That’s really good to know. I thought mine has been on at all times until yesterday when it went off and the alternator worked intermittently. Today as I was driving from Santa Cruz to Marin the battery/alternator light went out for about 10-15 minutes but the voltage didn’t increase like yesterday. So what, loos wire? Short inside insulation that occasionally connects or ecu? Is there another explanation? I bought a useless book hoping to find the other ends of the four wires in a diagram, they disappear into the harness going who knows where. I started un-taping the harness and found the one that goes to the fuse, if anyone knows where to find the other three so I can bypass with a new wire to test that would be helpful. If someone could tell me which of the four terminals is the one that has 12 bolts when it needs to turn on the alternator that would be easy to test . I was driving earlier, I’ll take a better look at the diagram posted earlier

 

Examine the harness carefully around the connector and give them all a little tug, I'd almost bet one is broken inside the insulation within a couple inches of the connector.

 

I will agree.
I think it was Muddinfun that chased just such an issue a few years ago.

 

Yes, I had to replace the connector a few years ago with about 4” of new wires coming from the new connector, solderspliced and heat shrink. I guess I can cut them open to be sure