Parking/Dash Lights Won't Go Out On My 2004 Tacoma

Hi Tacoma Experts,

I’m having a strange electrical problem that I have tried to troubleshoot myself but am out of ideas.

The dash and parking lights on my 2004 2WD standard cab Tacoma with 2.4L DOHC do not go out when I turn the combination switch to OFF.

When I turn on the headlights in the morning all lights work, head, tail, parking, interior, dash etc. After driving to my destination and while the truck is still running, I turn the combination switch to OFF and the headlights go out (good) but the dash and parking lights remain on (bad). Cycling the light switch has no effect. The parking and dash lights remain on. Even taking the key out of the ignition does not have an effect. The lights remain on. To get the lights to turn off I must restart the truck with the combination switch in the OFF position. Once I do that the parking and dash lights go out.

I have swapped the tail relay and the power outlet relay since they are the same part and it did not make a difference. I have also taken both of those relays out and tested using a multimeter; they behave the same way – open circuit until I apply 9V battery voltage across the coil and then around 1 ohm resistance between the circuit pins. Both relays behaved this way and I could hear them clicking every time I applied 9V. Conclusion: the tail relay is good.

I have swapped the tail fuse even though I did not see how it could possibly make a difference. It did not. Conclusion: not the tail fuse.

I have taken the combination switch off the steering column and checked the continuity through the pins at various switch settings (head, tail, off, low, high, etc.). I found continuity where I did not expect it and the pins did not match the picture I had (it appears to me missing a pin 10). So I ordered replacement switch from Rockauto and when it came I checked it out before installing it; it behaved in exactly the same way. Same continuity when off, same missing pin 10. I saw no point in installing it since it behaves the same way as my existing switch. Conclusion: not the combination light switch.

Now I’m out of ideas. They way I read the schematics, there are two switches in series for all those lights. One switch in the combination light switch and another switch in the Body ECU. The body ECU provide an auto-off feature so it must contain a switch. When everything works as designed I think those two switches provide a ground path that energizes the coil of the tail relay.

Has anyone else had this problem of heard of a similar problem?

Thanks.

 

Does this have a alarm or parts of one never removed ??

Add any electrical goodies when this happened??

 

No alarm, no aftermarket electrical of any kind. Totally stock basic truck.

 

No I added the towing harness about five years ago and haven't had any problems with it. I haven't even used it in two years.

 

Some place that circuit is getting a power source .

wires rubbed some place ??

 

I haven't found any short circuit yet but I haven't looked though the whole circuit yet. I have a hard time believing a short to power since it would have to be a short from a circuit that is still powered after removing the key.