Battery light on

Well I'm new here and my battery light is on. I have a 2006 Tundra that seems to be charging and the Battery along with Alternator checks good at O'Rielly's. Truck has started and run fine for the past month with this idiot light on but I'm 78 and just can't afford to be stopped somewhere without my truck running. I have tried most everything but I'm at wit's end with this problem.

 

Ahhh a first generation Tundra 2006.

The circuit for the "battery light" (Charge Indicator call by Toyota) is pretty simple. The instrument cluster gets power from the 10A IGN1 fuse and powers the "Charge" Light anytime the truck is on. The Yellow/Green wire coming out the bottom is the signal to turn the light on and off if there is a problem. Basically anytime this wire is grounded it completes the circuit and will make the "Charge" Light come on.

The Yellow/Green wire is monitoring the voltage coming from your alternator. The Body ECU is deciding if it is sufficient to turn the light On/Off. It seems yours is deciding it is not seeing enough voltage so it is keeping the Charge light on.

Have you put a multimeter on the battery to monitor voltage with key On (should be 12+V) and then with engine running (should be 13.5+V)?

 

The voltage, when running, is 13.86VDC. Everything seems normal except the dadburned idiot light being on!

 

I’m having this issue with our 2009 LX. Same 3UR-FE. Same alternator.

I was seeing random voltage spikes to 17 V. Noticed a bunch of corrosion on the battery so I replaced that. Tore the truck apart looking for water ingress. None found. It happened again after cleaning kick panel connectors, cleaning sunroof drains, and replacing the battery and the cowl grille (just in case water had been getting in and I couldn’t find it).

Next up in my list of things to replace was the alternator. Put a new one in from Toyota, and the dash battery light came on and has stayed on since installing the new alternator.

So, the alternator and battery are both new and both testing good, but the battery light is on. With a multimeter, voltage reads ~13.8 V at the battery terminals when the truck is running, and it reads 12.6 V in the morning after sitting all night.

The charging cable connection and the multi-pin connector both look good on the alternator side. I don’t know where all the leads go on the other end. Not really sure what to check next.

Any ideas would be much appreciated.

 

Leaving the battery disconnected overnight. Maybe that will help clear it? Feels like I’m grasping at straws.

What else should I check?

 

Seems odd you’re getting a light when the voltage seems good and a new part. Have you tried looking for any pending or stored codes through the OBD?

 

Yep, no codes.