I recently replaced the head unit on my Z (pulled out an older Pioneer PRemier) and upgraded to a newer Premier model. My goal was to add Bluetooth phoning capability, so I chose the DEH-p980BT Premier head unit, which does jsut about everything... pretty nice too.

Anyways, the upgrade didn't go well, and after the install I had some noises--pops, clicks, alt whine, etc... so I figured the new head unit was a little more susceptible to improper grounding or maybe I had a ground loop in my system. I have 3 amps, 2 signal processors, a 15F capacitor, and a bunch of other electronics (xbox360 which interfaces to nav, Sirius, IPOD adapter, TV tuner).

Well, I tracked down the ground loop, fixed the noise issues, and changed out 1 of my amps. THe car sounds great now...

Here is where the problem comes in... my interior lights don't work. THe car is always dark... the dome light is totally dead. I also checked the vanity mirror lights and they are dead too... and apparently after checking out the FSM (factory service manual), they are on a similar circuit, all being controlled by the BCM (body control module).

I started to debug the problem by checking the fuses and fusible links... all of which are good... so no blown fuses or links. I also made sure that there was continuity from the BCM output to the done light, and there is. I ran all the tests that Nissan would do, and all according to the FSM, and they check out fine, except for the output to the light. It appears that something got fried inside the BCM. The BCM controls other things as well, and is pretty complicated and I bet its not a cheap part. The FSM says to replace the BCM since all the other tests passed.

I am a little reluctant still...since I don't know why it went bad. Nothing I did when I rewired the new head unit should have done anything to the way the interior light circuit works....so I have no idea why it went bad (and yes the bulbs are fine, I checked).

Does anyone have any ideas ?? Its starting to look like I may have to drop my baby off at Nissan for further diagnosis, by the so-called "experts". I ahte to do that when I can probably fix it myself... but it appears that I may need a new BCM computer. Does anyone here have any parts like that, they are willing to sell ? I am not 100% sure thats the problem, so I am reluctant to dump a bunch of money into a BCM when it might not even fix it... but being without an interior light is a pain ! lol

Thanks for any help, and anyone with a BCM that they can sell, please hollar at me !

 

They would prob go and do the same things that you did, MAYBE. They prob would have just run a couple tests with the consult and said replace it. Electrical problems SUCK and it sounds like you've done most of the hard work. Changing your BCM means that you would have to reset the securtiy system and your keys. You can't do this yourself, you MUST have a consult. If I were you I'd just let it go. If you must swap it out contact a junkyard and pick one up. Should be $100 or less from them. I think it's $300 from the dealership. Then you'll have to go to the dealership and tell them what you want to do and I have no idea what they'll charge you, I'm guessing around $200.

 

UGGGH ! not good...

I may have to pull the existing bcm and see if I can fix it myself. Its probably just a transistor or a simple $1 part making that whole $300 computer fail, and thats usually the case. I defintely don't want to sink that kind of money into fixing a stupid light so that it comes on... lol

Everything else with the bcm works--the security, the door locks and keyfobs, etc... maybe I overlooked something, but I did check the 2 fuses that the FSM told me were related to that light circuit.

I will try to dig in a little deeper this week.

Oh yeah, about the junkyard... well, must be nice to have a junkyard with Z's on the lot... but not around here. I called last year for a part and the guy laughed at me anmd the junkyard is pretty big. He told me that anything newer than 2000 was going to be a hard find.... at least at his lot. So I may have to look elsewhere.

Any ideas if this might bew covered under warranty ? I did buy the extended warranty package through Nissan when I purchased, and its supposed to cover everything for a $50 fee. I don't think I did anything to casue this problem, but they will probably try to blame me for it, and that would void any warranty claims... has anyone had any experience with Nissan's extended warranty package and electrical problems ?

 

It can't hurt to ask but, if it's strickly a powertrain warranty it's not gonna apply.

 

GOT IT !

I guess in all the time I had the battery disconnected, something got hosed up... after verifying all the circuits, and checking for any possible shorts, and making sure the BCM was getting power (all according to the FSM), I opted to disconnect the ground for a few minutes, as sort of a reset procedure.

Well, that worked... my interior lights are back to functioning normally again. I knew I didn't mess them up during my install, and I am glad I didn't take it to Nissan for diagnostics and rack up a large bill over a computer that just needed rebooting.