Ok, went a'lookin', and came up dry. I am looking at the 97 wiring diagrams, and according to them, the turnsignals ground thru G102, which is 'near the PDC'...... and isn't shown well in the pics. G100 isn't listed at all...... Am I just having a brain-fart here?

Can you follow the doubled wires back to wherever it is they go?

 

The key here is systematic troubleshooting. You test one thing here and replace a part there, it would be pure luck to fix something that way. Here's what I would do:
- Disconnect all the rear lights from the wiring harness. The tail lights and license plate lights have connectors in the harness running to them.
- Check resistance to ground on each of the solid black wires at the connectors. Should be almost 0 ohms. If not, the problem is with the wiring running to the front.
- If that checks out, connect one tail light and see how it behaves, then disconnect it and connect the other side. Compare.

Let us know what you observe.

 

LIKE IT!!! I'm on it. Stand bye. Thank you!!!!!!!!!!!!!!!

 

Quick Question, DerTruck: As HeyYou mentioned, above, I know FOR SURE that one of the ground wires coming out of the black 4-connector grounding devices, right next to PDC, is not grounded. Shouldn't I fix that before doing the systematic, one by one, test of rear lights? I posted a picture of this black plastic connector a day or two ago in this thread. Just a thought

 

ANNnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnd one more thought, as I think both you and Hey You were providing insight(s) on my "Back up bulb" thread: It turns out that there is the flat 3157 bulb in both the turn/brake socket as well as the back up. Is there any way THIS could be my problem?

 

Okay. Very interesting. Ran a long wire from the negative terminal/cable at battery back to rear of truck and connected to one of my ohm meter wires. Then:

Disconnected the rear tail light connectors for both Driver & Passenger and ...it's a mess: Testing for continuity on the 4 wires - there was no continuity for the Black Ground wire, however, there was for both the Black & Yellow (Power?) striped wire as well as the Brown & Violet(Pink) on the Drivers side and same on Passenger where the Black Ground had no continuity, but, the Black & Yellow did as did the Green & Red. The other wire in both connector had no continuity.
The license plate lite(s), both black wires had continuity.

Didn't bother putting bulbs in one at a time as I know my wiring is screwed up. Just not sure what to do next.

 

If you are getting power back to the bulbs at the right time, just provide a new ground. Doesn't matter where, close to the lights would be easiest.

 

Okay. But forgive me again please but, if the wire that Should be power is grounded, as well as one of the other "non-ground" wires (has to be either brake or turn signal) is grounded, then how will the proper power get to the bulb - as you say - at the right time?

I could go splice into the black ground wire on both side and bolt the other end to the frame ...but then I'll have 3 grounded wires. How will that make my system (turn signals, brake, back up lights) work correctly?

Sorry if I'm not pickin' up what youre putting down

 

The various switches operate by supplying power to the correct bulb/filament. So, I think the hot ticket here is to pull all your bulbs, and test one system at a time. Do you get power to the socket on one of the terminals in there, when you apply the brake? Do you get power to that same terminal (switch on/off) with the turn signal for that side activated? Do you get power at the correct spot with the parking lights on?

 

First of all, Thank YOU for all your help!
I will take some time to test as you've instructed. Stay tuned for exact feedback.