Splice a connector to newer year taillight harness

2008 CHEVROLET SILVERADO

150,000 MILES • 6.6L • V8 • TURBO • 2WD • AUTOMATIC

MBEHR1983

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Okay, trying to pigtail 14-18 taillights to my truck listed above Duramax (harness is different). All was well except the turn signals were opposite after the switch. Since the switch I have been able to get power but no signal.
I know the driver side signal is yellow from the connector.
I know dark green is the signal on the passenger side.
I know black is ground and light green is reverse light. These are all from connector

The driver harness has Dark green, light green, brown, and black
The driver connector has yellow, green, black, brown

Passenger has dark green, light green, brown, and black harness and connector. Are these just color match?

I did a light test today and only brown had power with hazards on (not sure if my light tester can detect turn signals). I also have been trying to use multimeter but don’t get a reading.

Does anyone know what wires to connect from harness to plug?

Feb 12, 2022 at 3:07 PM

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KASEKENNY

CAR REPAIR CONTRIBUTOR
18,907 POSTS

We need to go to the BCM and find out what voltage we have coming out on the supply voltage circuits.

I have a feeling we are dealing with a BCM issue as it expects to see certain voltages returned and sent so we need to start with supply voltages for these wires.

https://www.2carpros.com/articles/how-to-check-wiring

However, are these replacement lamps, LED? If they are then I am sure that is the issue as the BCM freaks out when you replace halogen with LED bulbs that doesn't take into account, the difference in resistance.

Let's start with what we have at the BCM, and we can move to inputs from the switch. Basically, we need to find out if the BCM is getting the command but not sending it out.

Images (Click to enlarge)

Feb 13, 2022 at 5:03 PM