When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Hi, so I'll preface with saying I have dug around as much as I could to no avail with this issue. I have read multiple threads regarding the BCM as well as general fuse issues. So please don't think I'm asking blindly here. Onto the issue.
[Supporting Info]
I drive a 2008 G37 coupe 6mt
Recently had to drop my transmission due to the internal slave cylinder. Went with the CMAK kit from Zspeed. Installed a Southbend stage 2 clutch and lightweight flywheel in the process as well. Aside from all the connectors on the transmission (which i did indeed reconnect all of them) i do not recall disconnected anything else. I had the battery disconnected for the entire process, approximately 2 1/2 weeks. (did the whole job by myself aside from dropping the trans and putting it back "up", and it was the first time i ever did something of this size, reason for the extended time frame) Car started up PERFECTLY upon completion. Everything worked.
THEN I TRIED TO DRIVE HOME THAT NIGHT. :/
Tail lights were non-existent. Hmm.. Weird.
Did some research, which all points to these few "fixes"..."bring it to a dealer" / "the Body Control Module is fried" / "loose wires/connections" / "fuses"
Ill go in order.
Nearest dealer is over an hour away and quite frankly..After the hit i took on being down for more than two weeks with my transmission, I can't really afford a dealer visit, nor the chance of a ticket/impound on the drive home.
"BCM" - In the threads regarding this, people say that this signal junction also controls the signals to tell the dash lights to work, as well as the lights behind the controls for the A/C among others in the center console area. All of these lights still work for me however. Im also getting a signal to the Tail lamp fuse in the IPDM fuse box by the battery. (more on this later)
"loose wires" - I have jostled and pushed every connector i can find. Everything is connected, i quadruple checked every single spot i was working at. Including the fuse panel by the clutch pedal when i was changing the master cylinder for the clutch.
"fuses" the fun part... I checked all of my fuses for damage, All good. I then checked them all with a circuit tester, or a test light whichever you prefer, all were good. EXCEPT...for the tail light terminal. Correct, the fuse is fine. its the terminal itself that im finding fault with. When i test it, the right side of the fuse/terminal will light up. However the left side of the fuse/terminal will not. I say "fuse/terminal" because i tested with both the fuse installed, and uninstalled. Now OBVIOUSLY the circuit is broken with the fuse removed. I know that. BUT, i tried 3 different fuses. One was the spare from the drivers side fuse box, one was the original already in place, and one was from the A/C terminal. Which I know for a fact is working.
The ONLY other thing done to my car, is an audio system installed. However, I did not change the head unit. Just simply added in a amplifier/subwoofer. Which is still working perfectly, so that ground contact point (the one under the rear seats) is working flawlessly still as well.
More info, and a recap.
My blinkers work. My brake lights work. My high beams work. My front running lights work. My Reverse lights work.
The only lights not working are my actual tail lamps, the ones that come on when you're lights come on, and my license plate lamps.
As far as i cant tell, The BCM is sending the correct signals.
All ground points are GOOD
All connections are GOOD
The only known issue is in the IPDM fuse box, at the tail lamp fuse terminal where the circuit refuses to bridge over.
I've tried to be as specific and clear as I can. If there is anything I am missing PLEASE ask and PLEASE call me out on it.
I will answer all questions as best as I can.
Thank you to anyone who might be able to help or knows any information on this.
Last edited by 404_Lolligo; 09-28-2018 at 11:35 PM.
Reason: Forgot some info
The way I am reading the wiring diagram, both the front and rear parking lights feed off of the TAIL LAMP RELAY in the IPDM via:
Fuse 52/10amp (FRONT), and
Fuse 53/10amp (REAR).
There are no fuses in the interior/driver side fuse block for the parking lights.
If your front parking lights are working correctly, than likely the relay is okay. That said, if you are not getting 12VDC from the service side of Fuse 53, than likely you have a fuse or wiring issue from that point in the circuit.
The way I am reading the wiring diagram, both the front and rear parking lights feed off of the TAIL LAMP RELAY in the IPDM via:
Fuse 52/10amp (FRONT), and
Fuse 53/10amp (REAR).
There are no fuses in the interior/driver side fuse block for the parking lights.
If your front parking lights are working correctly, than likely the relay is okay. That said, if you are not getting 12VDC from the service side of Fuse 53, than likely you have a fuse or wiring issue from that point in the circuit.
Correct, all my front lights are working correctly. Its just at Fuse 53, like you said, on the service side. So fuse is fine, but the wiring on the "back side" of the fuse isn't receiving any power. Could it actually be a grounding issue?
It could be a grounding issue, or a failed solder connection, anything at this point. Attached is the breakdown for fuse 53. Assuming all other circuits on that branch are working, than your issue lies at junction 4G in the driver side fuse block where the tail lamps are spliced into the main branch. Or, like you mentioned, it could be a grounding issue. Sadly, it will be a lot of trial and error to find the culprit.
Last edited by ILM-NC G37S; 09-29-2018 at 02:54 PM.
It could be a grounding issue, or a failed solder connection, anything at this point. Attached is the breakdown for fuse 53. Assuming all other circuits on that branch are working, than your issue lies at junction 4G in the driver side fuse block where the tail lamps are spliced into the main branch. Or, like you mentioned, it could be a grounding issue. Sadly, it will be a lot of trial and error to find the culprit.
Correct in assuming all other electronics work in that circuit. So the issue does indeed fault with the 4G junction. So can that be narrowed down to either a bad solder that finally managed to break, a grounding issue associated with that junction, and lastly I would guess a possible issue in that branch of the wiring harness?
Just trying to narrow down possible causes, as I really don't want to just continuously toss money at this thing. Even the $15 pack of fuses i just bought will add up over time.
Just to clarify, fuse 53 is for illumination only. Do your control switches, cigarette lighter socket, glove box, and clock illuminate when you turn the lights on?
If so, then likely there is either a ground issue or other wiring issue on that tail lamp circuit. You could always disconnect the harness at the tail lamps and run 12V directly to them to see if they work. At least that will help you narrow down the problem.
Just to clarify, fuse 53 is for illumination only. Do your control switches, cigarette lighter socket, glove box, and clock illuminate when you turn the lights on?
If so, then likely there is either a ground issue or other wiring issue on that tail lamp circuit. You could always disconnect the harness at the tail lamps and run 12V directly to them to see if they work. At least that will help you narrow down the problem.
They do work, well the glovebox and clock are out, but i think thats actually just the bulbs, i dont recall them ever working. The cigarette socket is working as well as the control switches however.
And my brake lights do work, so i know that the lights (housing) themselves do have the ability to illuminate. I will do a direct 12v test tomorrow just to make sure the "taillamp" wiring is still good on them, though i wouldnt expect both wiring harnesses from the housings to go bad at the same time.
So i do indeed think its an issue between the two. So either a ground issue or POSSIBLY a cut or broken wire in the harness leading to the back of the car. i did have the center console removed when i did the transmission work so i guess there is that possibility.
Another simple test: do the switches on your steering wheel light up when you turn the lights on? Just trying to narrow down the anomoly. With both the clock and the glove box not lighting up adds to the gremlin.
If it were me I would check for power at pin 4G (red wire) on Connector B6 (brown, 12pins) at the Fuse/Junction box. If there is power at that pin, than likely you have a ground/wiring issue down the line.
Alternatively, you could isolate that pin (4G) and apply battery power directly to that red wire. Again if the lights still do not work, there is a ground or other wiring issue.
After looking over the wiring harness layouts I do not see anything in/on/or near the center console that would contribute to this problem. Harness B6 is the main harness from the Fuse/Junction box to the rear lamp assemblies and that runs along the driver side door sill.
Another simple test: do the switches on your steering wheel light up when you turn the lights on? Just trying to narrow down the anomoly. With both the clock and the glove box not lighting up adds to the gremlin.
If it were me I would check for power at pin 4G (red wire) on Connector B6 (brown, 12pins) at the Fuse/Junction box. If there is power at that pin, than likely you have a ground/wiring issue down the line.
Alternatively, you could isolate that pin (4G) and apply battery power directly to that red wire. Again if the lights still do not work, there is a ground or other wiring issue.
After looking over the wiring harness layouts I do not see anything in/on/or near the center console that would contribute to this problem. Harness B6 is the main harness from the Fuse/Junction box to the rear lamp assemblies and that runs along the driver side door sill.
Its dark and raining where i live so ill be trying this tomorrow, I appreciate the suggestions and will update when i find out anymore information. Thanks again
09-28-2018, 11:22 PM
