high beams stay on

[niceguypmp3]

on my '03 TB today, once i got home and shut it off and went to walk in the house, i turned around and the high beams were on. The headlights were on this afternoon while driving because of rain, but I never turned on the high beams nor was the indicator on. So I tried different combinations of turning the ignition back on and off, the headlamp switch on/off and the dimmer switch back and forth and the only way I could get the high beams to shut off was to pull the relay under the hood momentarily then plug it back in. Now they stay off until i turn on the high beams, then they stick on again until i pull the relay. The low beams are working correctly with the dimmer switch. It's just the high beams that stay on constantly.
Does anyone know what the heck could be wrong? Could it be the dimmer switch gone bad? I hope they are easy to change. Or could the headlamp switch do this? Any ideas???

 

[Blckshdw]

Try swapping the relay with the windshield washer relay next to it. If the odd behavior stops, (or your windshield washer starts running constantly) then you know you just have a faulty relay to replace

 

[niceguypmp3]

I did swap the relay with the one next to it and still the same behavior. Once the high beams are turned on, they stay on until the relay is removed. Then when it is reinstalled, they stay off until they are manually turned back on.

 

[Blckshdw]

Looking at the schematics, a ground signal goes from the turn signal switch, back to the BCM, which grounds the high beam relay. Are you handy with a meter at all? I'd want to test and see if the input to the BCM is open, or grounded when the high beams are stuck on. If it is, then the switch is probably the culprit.

ETA:

 

[niceguypmp3]

hmm... I dont know if i should attempt that. My next question is how the heck did the high beams get on to begin with? I never turned them on. The turn signal switch never got pushed forward to high beams today and i never saw the high beam indicator on the instrument cluster. I sure hope it's not the BCM messing up!

 

[niceguypmp3]

surely the problem is either the turn signal/multifunction switch or the BCM, correct? Is it the BCM that's attached beside the underhood fuse block? isn't a BCM under the left rear seat too? Which one would control the high beams? Which would you suggest changing first as it may be the culprit. Neither seems to cost too awful much, except that the BCM might need a visit to the dealer to program the new one. Why did they have to make the electronics on these vehicles so complicated that now even the headlights control goes through a computer, jeesh.

 

[Blckshdw]

The BCM is under the rear seat next to the fuse block, the PCM is the one that's on the engine. If you focus on the right most sides of both those pics, you can trace the path from the turn signal switch, through the BCM, to the front fuse block and relay, out to the headlights.

May take a little bit of a learning curve and a youtube video or 2, but testing for the ground signal to confirm where the problem is coming from is the best practice. Having that knowledge in your back pocket can always be used for future troubleshooting as well. That's my recommendation.

But yeah if you get a new BCM, it will need programming. A used one from a junker can be dropped in, just have to wait for the security relearn that takes about 30 minutes.

Edit: If the dash indicator is only on when you have the switch activated, and turns back off when you turn the switch off, but the high beams are staying on, that tells me the BCM isn't seeing the signal from the switch. The problem could be the BCM, or it could be something between the BCM and the relay that's grounding out and activating the relay.

 

[TJBaker57]

A used one from a junker can be dropped in, just have to wait for the security relearn that takes about 30 minutes.

If you swap in a used one and it came from a truck that does not have certain options your truck does, like a sunroof or foglights, then those options will not work in your truck. Also your factory radio will lock out.

Here is the light green wire from the switch at the BCM, between the white and purple wires...



And this is the Black/white wire from the BCM to the high beam relay.....

 

[niceguypmp3]

wow, thank you for the pics and information. now, for me to figure out the problem, how should I test those two wires; the light green and the black/white wire? While the high beams are stuck on, should either wire be hot? I do have a multimeter, i just need to know what to look for with those two wires. Again, thank you for the help!