Notice this morning that my keyfob didn't work. Opened with the key then found that the door lock/unlock also didn't work. Did a once over to see what else was up and found that all the dome lights including the door ajar lights didn't work. Everything else was good...dash, radio, windows etc...

Found that no fuses were labeled to anything that didn't work, but checked some I thought could have been blown. All were good.

Any ideas if there is a fuse I missed? Relay? Got any schematics.

Appreciate the help.

 

i think it is the fuse that is in the middle row all the way to the left, i dont remember what it is labeled but i think it is "electrical _______" If that one isnt blown, start working your way through all the fuses because i can almost guarantee that a blown fuse is your problem.

 

Done any drilling lately?

 

No drilling done at all. I pulled the 10A Electrical System fuse and it ohmed good. In fact, I checked all the input fuses to the SECU and they all ohmed good. Battery was 12.69v no load. My red security led is also flashing okay. I think something's up with the security membrane a.k.a SECU. I haven't checked the voltage pinouts on the SECU harness yet. According to the SECU wiring diagram, it's like half the functions work. Also noticed that there are no door open "ding-ding" sound. Probably indicates that the door switches don't work either....so pretty much, no alarm system, FREE to thieves...

Appreciate the help from anybody...

 

Forgot to ask, has anyone ever replaced the System Entrance Control Unit?

 

Either I missed it - what year/model do you have? I can take a look at FSM but I need exact year/model. Once upon a time I tried to help with similar problems and it came down to fried FET in Smart Entrance Control Unit which provides this battery saver feature. In that case the owner was simply replacing the bulb in his trunk and accidently shortened bulb's socket. Trunk light was on and the bulb is powered through that FET, so ... he bought and replaced the unit. I believe, you'd need to let the new one learn your remotes. It was 2k model if I recall correctly.

 

Thanks for the help. It's a 2000 GXE. I figured I'd have to get a relearn if I replaced the entire SECU. hoping not to go that route...

 

maybe i missed it but did you check all your other fuses? About 3 months ago i had all of the same functions as you stop working and it ended up being a fuse.

I may be wrong but you might as well take the 3 minutes it takes to check all the interior fuses before you start pulling things apart.

I also remember that when i went through and found the blown fuse and replaced it it didn't fix the problem, so i went through a second time to see if i missed something else. I didnt find any other blown fuses but after pulling and replacing all the fuses for the second time everything worked. I don't know if i somehow preformed a reset procedure or for some reason the fuse wasn't making good contact but hopefully you can use that information... I hope i at least helped a little

 

It's more than likley a blown fuse. I don't have 5th gen wiring diagrams but if you had a 4th gen I could tell you which fuse. I don't believe the wiring & electrical sytems were changed that much between the 4th and 5th gen. 4th gen has one fuse that controls the buzzer, step lamp, doorlock, remote, illumination, theft system and windows. I would think 5th gen is similar.

 

The same circuit also powers vanity mirrors, key hole illumination and trunk lamp. If those don't work as well you could swap with others fuses #10 & 12 of Fuse Block - Junction Box. They both called "Electronic Parts". If they both are good then I'd say you have the same problem as one in the past - the power transistor in SECU is gone. It powers terminal #17 of SECU which powers all those devices. Check those 2 fuses first, of course.

 

So I replaced my battery and all the 10 and 15 A fuses in the fuse box. No change. Checked voltages at the SECU. I got the 12V input supply on the M40 connector. Also got 12V on M41 connector for ignition ACC and ON positions. However, all the 5V signals on M41 are missing. I'm looking at my wiring diagram to trace M41 back, but if anybody know, that'll help. In the meantime, I'm also headed back to the 'Zone to get more 10,15,20A fuses to replace them in the fuse link under the hood. So, I think it proves that my SECU is good, my fuse box is good, and the problem is from wherever M41 comes from.

 

Did you see 12V on terminal #17 of M41 connector? This is battery saver output. You didn't most likely.

The 5V signals are all results of external switches connecting corresponding terminals to the ground whenever needed, they all 'sensor' inputs with some resistors connected to internal SECU 5V power line inside SECU. If you see none of those voltages then it would mean the internal SECU 5V power supply doesn't provide 5V anymore which fits the rest of your problems. There's no external 5V power supply line going into SECU, it makes it internally from 12V going through terminals 10 & 11.

So, in my opinion you most likely have a bad SECU. If you're electronically inclined you can try to fix it otherwise the only option is the replacement.

 

O.K. That makes sense. I take it the SECU has field replaceable components? I work with some guys who are really good at troubleshooting down to the component level, so I'll go that route first. Quick question again. How do I emove the SECU? I didn't see any bolts holing it down.

Thanks.

 

Well, I recall it had a lot of SMD components. OTOH the 5V power supply could be simple 7805 - descendant chip which should be fairly easy to replace. I don't remember how I removed the SECU few years ago, sorry.

 

I got the SECU removed and will open it up at my shop tomorrow to take a look. If I need a new SECU, all I would need is a relearn for the remotes? I was thinking of going to the pick and pull yard and swapping it out with a similar model GXE. Then I got to thinking that if I swap it out, it my activate NATS. Any likelihood of that happening? I can wait a few days to get the remote relarn if necessary...

Much appreciate your help.

 

As far as I know SECU has nothing to do with NATS, so it should be interchangeable. While remote and chip inside the key are physically close they talk to completely independent systems. Key chip is read by ECU itself by using coil around key hole. It requires dealer equipment to get ECU to learn an extra key while learning new remote requires nothing besides the car and all the remotes.

 

Sorry if I had asked this before, but is the SECU a plug-n-play deal?
Contemplating whether or not to pull it from a yard or new from Courtesy Nissan, and then attempting to reprogram they keyfob myself. If I had to reprogram the keyfob guaranteed, then I'll just go with a junkyard.

 

I don't think you'll notice any difference between new SECU and the one from j/y. In both cases you'll have to let it learn your remotes, all of them. Other than that the rest of connections are not car specific, they're just switches/bulbs/relays.

 

did you ever figure out what your problem was? This is info we could use to help others in the future...

 

Found a yard in WA that had an SECU, ordered it and expecting delivery tomorrow. I did open my broke SECU. Everything is pretty much all surface mounted so could't replace anything. I did hook up a 12V supply to the inputs and tested the pinouts straight from the SECU. As with previous posts, my 5V are missing and my battery saver output (#17 of M41) was 8.49V...should be 12. Thanks Max5gen for the helps. Will let you guys know how the install and my first attempt to reprogram my keyfobs go.

 

You're welcome. Just to explain your voltage on #17: if you didn't load it with resistor say 1 kOhm to the ground then what you actually measured was closed FET leak current (very low) multiplied by your voltmeter resistance (very high). If you'd put any load there you'd measure the actual voltage which would be very close to 0V. This is more of academic exersise of course and doesn't help you with the problem at hands. Did you see a 7805 -ish chip in there? They could stick it to the wall of SECU enclosure to provide better heat dissipation. OTOH they could also put a step down switcheable power supply which you wouldn't recognize that easily. This is also just to satisfy my curiousity as I'm too lazy at the moment to pull my own SECU out and see for myself .

 

O.K. Job done! Hooked up the SECU and did a keyfob reprogram. Tested all remote functions and they where cherry. Buttoned it all up washed that *****!

PS. There was a 4 post FET in the SECU. I didn't take any voltage measurements on it, but it was surface mounted and didn't look field replaceable. Oh wells, glad everything's working now. Much thanks to Max 5gen for the expertise.

 

Check your fuses bro

 

Glad I was of some help. If it is not a secret - how much did you pay for the SECU?

 

$100 + shipping

I made sure to look for one with an exact match to the nissan p# printed on the unit. I think it was 285902Y or something like that.

 

So I had these same issues but had trouble finding a SECU at a local junkyard. I'm glad I didn't because...

THERE MIGHT BE AN EASIER WAY!!

****Try disconnecting the two plugs going into the SECU, waiting 5 seconds and then reconnecting them. After about a year of no interior lights, power door locks, and rear defrost.... they all work!! The first time I plugged them back in the horn started honking like the car alarm going off and again when I opened the trunk. So the second time I made sure the keys were in the ignition and turned to accessory, unplugged the plugs and reconnected them starting with the white plug first. After this I had no more alarms. Also, FYI I took off the kick panel under the steering wheel by removing two screws to make unplugging the unit easier.

This is the box that I assumed to be the SECU:



I found this thread: http://x.nissanhelp.com/forums/maxim...defroster.html and thankfully tried unplugging it before buying a brand new unit from a dealer. Finally no more using a flashlight inside my car!