Backup Lamps Inoperable (post 1/2)

[Hayk]

When I first purchased my 2012 9C1, the rear brake lights, turn signals and backup lamps were not working. Not really a surprise as this was our 2nd caprice and Id worked with a few others before and I knew something was snipped somewhere. This write will focus on how and where, I found the backup lamp wire cut. With a big help from Steve Walker of course.

At initial glance at the BCM while doing a G8 console swap (shortly after purchase), I noticed cut wires. For the most part it was pretty obvious which wires needed to be connected back together (After I confirmed with their respective pin-out location and the respective BCM connector (X1, X2, etc...)).

After everything was reconnected, the backup lamps remained inoperable. So, below we diagnose the problem.
The diagram below will need to be utilized to follow the path from BCM connector X4 pin 24 to taillight connector. The diagnoses is essentially performing continuity testing between relay (more than likely top right relay pin) and connectors to determine where the wiring may have been cut. You will need about 15-20ft of wire to support continuity testing from relay to connectors located in the trunk area.

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1. Double check BCM X4 pin 24 to ensure it is intact and the wiring to and from it in the immediate area are secure.

2. KR40 Relay connection/fuse block under hood, find it.

Using multimeter I found the two lower pins had voltage when red lead went into pin and black lead was ground on engine block. Need to note these two pins (for me, most forward two pins) so we do not use them in our diagnoses.

Now for the other two pins at the relay, we test for ground using positive battery post. For this effort, key should be in “on” position and shifter in “R” position (be sure to use E-Brake). For Top left I got 12v (for BCM) and for top right I got nothing (must be going to taillight).

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So, we know there is a break between relay and taillight. So we will perform continuity test. I had to use one 10ft blue wire and one pink 10ft wire to have a long enough wire to support continuity testing. Run the red lead to top right pin, run you continuity wire from black lead to taillight male connector on vehicle side. Probe the pin with the light green wire.

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Still no power so we move to the next connector.


3. X404 connector (resting just above passenger wheel well behind trunk lining) pin #2, once again light green wire (not to be confused with dark green wire beside it).

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[Hayk]

First, check continuity from female connector to taillight connect. It’s a short run but that location sees more use.

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Second, check continuity on the male connector. From light green wire pin/cavity to black lead of multimeter.

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Still had no voltage, so there was a power break between X404 and X206


4. X206 connector (resting behind the right plastic kick panel on the passenger side, see below for general location)

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Here is what the connector looks like, we are interested in the light green wire going to pin #3.

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For me, the break was very obvious.

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I was able to get the terminal (for pin #3) to release after finessing to unplug the connector and unlocking the terminals.

After I reconnected the cut wire, the backup lamps worked as they should!



If you still do not find a break in the wires up to connector X206, the only location it can be in is between X206 and the relay. You will just have to chase the wire to the relay to find the break.

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[Turbopowered68]

would this be the same for the 2014?

[smwalker]

Similar approach but all the connector numbers and locations will be different.