sjtangb25

Hi Guys,

My reverse light stopped working when gear in reverse. I checked the fuse and it is is fine. After my research I believe it is my reverse light switch. I jacked up the car and been down there for 20 mins looking for the switch and I just can not seem to find it. The car is 2006 with auto tranny. Please tell me where it is or best someone has a photo of it's location?

CG

Dano523

Your looking for something that does not exist on the A 6 trans. Hence only the M6 has the reverse light switch on the passenger side of the trans itself.


Backup Lamps, A6 trans
The underhood fuse block supplies battery voltage through the STOP/B/U/ LPS fuse to the coil and switch terminals of the REVERSE LAMP Relay located in the body control module (BCM). When the transmission is placed in the REVERSE position, the transmission control module (TCM) sends a class 2 message to the BCM. The message indicates that the gear selector is in the REVERSE position. The BCM grounds the back up lamp relay control circuit of the reverse lamp relay . This energizes the reverse lamp relay, closing the switch side contacts and provides battery voltage to the REVERSE LAMPS fuse through to the backup lamps. The backup lamps are permanently grounded at G302. With both power and ground the backup lamps illuminate. Once the driver moves the gear selector out of the REVERSE position, a message is sent by the TCM via class 2 serial data requesting the BCM to remove ground from the REVERSE LAMP Relay control circuit. This opens the REVERSE LAMP Relay switch contacts turning OFF the backup lamps.


As for your back up light relay, its on the bottom side of the BCM, and indicated by the broken dash lines.


So could be a problem with the TCM (it in the trans), could be a problem with the BU light relay on the bottom of the BCM or reverse lamp fuse on top of the BCM, could be a problem with the BCM itself, or could be a problem wiring problem from the BCM connector (C3 connector, D9 pin, L-gn wire), to the C445 connector in the rear fender void location, out to the back up lights, then to ground.

The C455 connector will be inside the rear fender void area on the passenger side when you pull the rear tail light to look isntead, and a good place to check on the L-Gn wire pin to ground with the car in reverse with a test light to ground, to see if your getting power to there to begin with. This weed out if the problem is before, or after the connector and which way you need to start chasing.

As for if the problem is at the TCM level, Tech II makes quick work of this, since you are able to check the data on both the TCM and the BCM to see if the they are indicating the trans in reverse to start with. If both TCM and BCM are showing car in reverse, then would bank that the problem is the BU relay on the bottom of the BCM or reverse fuse (send row from the left, top), if not a wiring problem to the back of the car.

PDF of the back up wiring for download, and forget all the back up switch parts bottom middle of the diagram for the most part, since that is for the M6 trans only. So for you, its the TCM to BCM on the left bottom, The MYC loop center bottom only, then far right bottom of the wiring out of the BCM to the BU lights instead.
https://www.mediafire.com/file/kkwgr...liner.pdf/file http://www.mediafire.com/file/kkwgrw...liner.pdf/file

To add, if our going to wrench on the car, you really need a Tech II.
Also, GMSI ( or at least repair manual in hard copy form) comes in handy to make rhyme and reason of the system and where I pulled the PDF and information from to start with for your car's problem.
https://www.corvetteforum.com/forums...ternative.html

sjtangb25

Hi Dano523, I really appreciate you take your time to answer my question. This sounds like I better of to take the car to the shop to deal with since I really don't have a tech II.

sjtangb25

One more questions, I just took a photo of my BCM and can you tell me which one is the BU relay?

TorchRedFred

sjtangb25

Oh, thanks Fred!

74plb

From Just answer, it shows the bottom relay on the backside of bcm to be the bu relay.
Tried to post an image but my phone isnt cooperating

sjtangb25

Hi,

I just want to thank everyone who help with advises and the problem has been solved. It turns out it is the back up lamp relay. I went down to my local dealer and pick up this relay for $10! I am so happy this problem has been resolved!!.

CG

Dano523

Good on you mate for solving the problem, but the BU relay's are not know to be one of those items that tend to go south on a regular bases.

So seeing all the wiring you have in the BCM areas, going to guess after market radio with back up camera with the back up camera positive power supply tired into the back up light circuit. So on that note, would check to see how much power the BU camera positive wiring tied into the BU lights is pulling from the circuit through the relay to start with, that is not putting too much additional load on the relay to begin with, and the BU lights are going out once you do take the car of of reverse so the Bu relay is not over heating from too much use instead.

sjtangb25

Dano523

With the cluster of wires you posted, pull the back up lights, and test them for both a short to ground, and then see what is tapped into the back up light wires that is pulling a higher than OEM load that is taxing the relay to cause it to burn out so quickly.

My guess, is that the back up light wires where tapped for a back up camera back to the radio, and its going to be the back up camera wire that is grounding out to cause the relay problem.

sjtangb25

tlcj

I will take a guess or throw out an idea. If your backup camera is drawing more current than the backup light relay can handle then you need to reduce the load. In cars, many times a relay is used. The current to power a relay can be smaller than the load you are trying to power. Let the BU circuit power a small relay and use the relay contacts to power whatever you need to power using another power source. I am not sure if you need to provide power or a ground. I have not done head units in many years. It seems to me that you are burning up the BU relay. I am amazed at Dano523 and how he already knew your issue might return.

Dano523

Ditto with this, since a 30amp 12 relay will only draw around 450ma on its coils trigger side, and it alone connected to the BU lights will not increase the load on the BCM relay to burn it out.

So wire from 86 goes to the BU light wires, and 85 goes to ground. When the BU lights come on, the relay will only pull around 450ma when it energizes and connects terminal 30 to 87.

Now with a fuse in line, we wire 30 to the battery positive terminal, and then the items that do need power when the back up lights come on, are wired to terminal 87 (normal open, until the coil is energized to close the circuit).



Also, when you are cutting all the after market wiring connected to the Bu light wire, double check the added wire running back to make sure it not grounding out with a short to ground. Hence we are moving the power draw of the after market items off the BCM relay, to the added relay and if one of the after market wires are grounding out, it just going to blow the fuse off terminal 30 to battery positive power isntead.

If you check around, should be able to pick up a SPST 12v 30 amp relay with harshness for under $10, and in line fuse holder included for around $10 total.

Dano523

Hence seeing this cluster of wires mess, tells me that there is more wired to the back up lights than just a back up camera, and why the BCM relay is burning up with too much a draw through it isntead.




Worse yet, the ground splice block has been unclipped for where its normally clipped in place, and makes me wonder is someone added a ground wire to the wire leading back to a chassis ground point, isntead of running the ground wire all the way back to the chassis ground point isntead.

sjtangb25

Does the ground wire to the wire leading back to a chassis ground point, instead of running the ground wire all the way back to the chassis ground point instead makes a difference? If so how are the two causing or effecting my issue?

Dano523

Number 5 is the chassic ground point, While #1 is the sp208 ground spice block instead.
Hence GM throw in a bunch of splice blocks into the car to save money on added lengths of wire, but the wire from the splice blocks to the actual grounding point, was not over sized enough to take much more of a load that what GM designed to carry that load. And it not just the wire size in the car, but the entire circuitry as well in the car too that was not de-rated enough to start adding loads to them as well.


So in this photo, on the left you can see a finger nail, and to the right of it is the silver box with black tape that is SP208 that a lot of module as using for grounding, that I still can't tell if someone tapped into the ground wiring.



So to sum it up, you can't tie into the factor wiring to pull much more of a load from any circut, and with the amount of after market wiring I see roped at the BCM location, makes me wonder what elese was tapped into the factor wiring to cause problems as well. We know that the BU light wires has something tied into them to over load the BCM BU relay, so really need to go through the rest of the aftermarket devices as well to see if the are over loaded as well.

I'm guessing that there is an after market amp in play with all the speaker wire I'm seeing, and although an after market radio converter can be used for the amp trigger wire, there is no way in hell enough power on any of the radio circuits (including a bose amp power wire circut) to tie the power for the after market amps into them. Hence you have to look at the BCM itself as needing X amount of power, and if too much power is being pulled from the BCM pre output fuses, it could be causing the problem with the BU relay going south too soon as well.

Hence we have the BU light Fuse for the load side of the BU relay, but the coil side of the BU Relay is pulling powder from the BCM fuse isntead. So too much of a draw from the BCM's own power, could be causing the short life of the BU relay itself on the coils side.

So again, figure out all the after market items in the car pulling power, and then see where they are pulling power from to start with. If from the factory wiring, going to cause problems, since the factory wire is only gauge sized to pull just enough power from the OEM items alone.