The Dreaded Instrument Panel Lights/Aftermarket Radio Issue

Hi all,

I have a new (to me) 2002 Double Cab 2WD PreRunner (more of an intro below). I bought a nice new head unit with CarPlay from Crutchfield and followed their installation instructions. The first time I turned it on, I noticed the dash illumination (in this case, specifically the two little bulbs that illuminate the AC controls) flicker a few times and then go off. Later, I did find the tail light fuse blown and replaced it. Crutchfield advised me to snip the illumination wire on the harness and cover it off (orange from their harness, either orange with a white stripe or white with an orange stripe, I believe, from the Tacoma - if the right thing is to snip it, why even connect it in the first place?). That still didn't fix the problem.

I've rechecked all the fuses and also checked the tail light relay - all good.

I've been searching and have seen all the threads about taking the dash dimmer rheostat to ground. However, I'm unclear on exactly what to do. The connector on the back of the dimmer dial has three wires into it:

• Green with a red stripe (12v I believe)
• White with a black stripe (ground?)
• White with a green stripe (also ground?)

How exactly am I supposed to bypass this rheostat? By the way, is there any chance this rheostat could be blown?

One last question: is it even within the realm of possibility that every single dash illumination bulb blew?

Thanks,

Todd


Further Intro:
2002 Double Cab 2WD PreRunner
140k miles
I'm the third owner: my dad bought it from a truck at only a year or so old and has had it since then. Mom and dad no longer need two cars so he passed the Tacoma on to me to use as my tow vehicle (lightweight trailer, lightweight race car). I've added a rack and an awning for shade on race days.

 

I believe they are saying disconnect that wire from your head unit harness, not from your truck. Just cut the wire on your adapter harness so the head unit's dimming function isn't interfering with your dash lights.

 

You are correct, which I have done. Didn’t fix the issue.

In reading the forum, it seems that this dash illumination issue is common when installing an aftermarket radio. I’ve seen references to bypassing the dimmer dial rheostat (the dial to the left of the steering wheel) but I’m unsure on which wires to ground from that connector.

 

If you removed the wire, there's nothing tying your head unit to your dash lights or the rheostat.... just your AC control lights are having the issue?

 

Sorry for the delayed response - I've been busy.

It is not just the AC control lights that are having the issue. Looking at the FSM, there are a bunch of illumination lights connected together that are not working: hazard switch, rear diff lock, AC control, cigarette lighter, ashtray, glove box, auto tranny selection, O/D, the gauge cluster lights, and maybe tellingly, the taillights.

Brake lights work. Turn signals work. Power ports work. Aftermarket and factory radio (when I plug it back in) work (orange wire has been snipped).

But, when I turn the lights on, I don't get taillights. I had a chance to check and there is no 12V at the Green/Red wire on the illumination dimmer rheostat (so I don't think it's a bad rheostat). Fuses are good. Makes me think there is something loose somewhere, though I feel like I have checked everything. I'm wondering if it is specifically with the taillights. I also installed a 4-pin to 7-pin converter for the hitch and I'm wondering if there is a bad ground or connection there.

Any other ideas are welcome. My current plan is:

• Check the taillight assembly for proper ground and power.
• Trace the 12v power to the illumination back to the source using the FSM and then check all the way through to see where the fault starts.

Thanks,

Todd

 

This is almost certainly the culprit. The circuits on the truck are usually ground switched, and those trailer harnesses are notorious for causing the issues you're describing.

 

Andy - Thanks. First, I'll unplug the 7-pin harness and see if that fixes it. Do you have any advice, if this is the issue, on how to fix it since I do need to have a 7-pin harness? Cheers, Todd

 

I have a 4 pin Curt (56496) that was recommended by someone here Obviously not helpful for you.