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Discussion Starter #1
Hi, I thought I'd make a separate post on this one...and this has stumped many so far. It is a very minor issue, but if someone can help me solve this...I will paypal you money for a beer or something, even though I don't drink...

OK, I just bought a 2008 MDX with navi, RES, etc. Everything works perfectly. Love, love, love the car. I would take it out in the middle of the night just for kicks to get coffee (decaf) and I am deliberately driving the kids to school daily in it instead of letting them take the school bus. It is really a wonderful vehicle. And I have tested everything and it works and I got a super duper deal on it (full ADS shock replacement from Acura at no cost to me).

So...the only thing here is that when I start the car (like start start, with the engine going), it pops up the screen and asks me for the nav 4-digit code. Every. Single. Time. It is not big deal because what is entering 4 digits with that wheel, right? But it happens all the time. Now...I know what you may suggest...change the battery...

I changed the battery on Saturday with a brand new 24F AGM one. Brand new, manufactured last month. Car runs great as usual. No issues. Had to enter my radio code too but that was normal.

Since then, I have had to enter my navi code once again every single time the car starts. Here's the strange thing - if I move the key to position II (so not started, but you see all those lights on the dash), the navi does not ask for the code. But once I turn the car over and start the engine, it asks for the code. I enter it in and the navi can be used as normal.

The radio has not asked for any code and retains all stations and pre-sets.

And...on top of it, I got into the diagnostics screen (map/guide + menu + cancel) and ran all the diagnostics. The navi unit checks out OK on diagnostics, and so does the ECU and everything else connected to the navi ECU. I reloaded the software, wiped out the memory and started over and it still does the same. Clearly not the battery.

I went into the local Acura dealership and talked with three techs. None of them has seen this issue before. Ever.

Someone here on this board suggested checking some "saved memory" fuse. I looked in my manual and don't see anything like that. On top of it, if it was a memory issue, wouldn't the radio settings and the rest of the navi settings all be reset as well? It is just the code that is being asked every time, and only on start up, not position II (that is the strange thing).

Any ideas would be appreciated. Winner gets some paypal money for a beer/coffee or other beverage...:grin:
 

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My initial approach is this, every coded device (radio or NAV) has at least two power wires. One power comes directly from battery and it is never powered down (It could be called memory BACKUP power for our purpose). This keeps the memory going and it is used as theft protection. Whenever this power goes down, the device will ask for code next time it is powered up. The other one is power ACC. This is the ON-OFF power that we normally see when we turn the ignition key. Then, there are other connections from lights ON or sun light sensor for night adjustments,..., etc.

The other day, I adjusted the valves in my MDX. During the process, I had to disconnect many wires in the engine harness. I remember that when I finished and went back into the car for a test drive, one device asked me for the code. I do not recall if it was just NAV or the radio that asked for the code. But I remember it was odd that only one device asked for the code. By the way, I did not disconnect the battery for the whole maintenance. I was not expecting any code to be needed. So, I will check it out tonight which code it was. So, whatever I disconnected for doing the service, affected the power for such device forcing the device to ask for the code again. After the code was entered, all went back to normal and no more code is needed.

So, in my opinion, it is a loose wire connection, a broken wire, or maybe even a fuse. The idea of the fuse, as originally suggested in another thread, makes sense because all wiring needs to be protected from short-circuits. However, the fuse would not be called BACKUP fuse anywhere even though that is its function (theft protection) as I described at the beginning of the message.

Do you have the service manual to look for the wiring schematic? If not, I can take a look at my manual and can give you some hints of what connectors to start looking at.

My 2 cents.
 

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Discussion Starter #3
My initial approach is this, every coded device (radio or NAV) has at least two power wires. One power comes directly from battery and it is never powered down (It could be called memory BACKUP power for our purpose). This keeps the memory going and it is used as theft protection. Whenever this power goes down, the device will ask for code next time it is powered up. The other one is power ACC. This is the ON-OFF power that we normally see when we turn the ignition key. Then, there are other connections from lights ON or sun light sensor for night adjustments,..., etc.

The other day, I adjusted the valves in my MDX. During the process, I had to disconnect many wires in the engine harness. I remember that when I finished and went back into the car for a test drive, one device asked me for the code. I do not recall if it was just NAV or the radio that asked for the code. But I remember it was odd that only one device asked for the code. By the way, I did not disconnect the battery for the whole maintenance. I was not expecting any code to be needed. So, I will check it out tonight which code it was. So, whatever I disconnected for doing the service, affected the power for such device forcing the device to ask for the code again. After the code was entered, all went back to normal and no more code is needed.

So, in my opinion, it is a loose wire connection, a broken wire, or maybe even a fuse. The idea of the fuse, as originally suggested in another thread, makes sense because all wiring needs to be protected from short-circuits. However, the fuse would not be called BACKUP fuse anywhere even though that is its function (theft protection) as I described at the beginning of the message.

Do you have the service manual to look for the wiring schematic? If not, I can take a look at my manual and can give you some hints of what connectors to start looking at.

My 2 cents.
PrGonzalez, thanks so much for the input. I don't have the service manual. And while the fuse would make sense, I have no idea which fuse it would be. Even in looking at my owner's manual, I can't see what fuse would control this - it is definitely not obvious.

What still stumps though, is why it does not ask for the code when I put the key in and set it to position II. In this case, it just goes to the acknowledgment screen. But then when I crank the engine, it asks for the code.

Thanks again for your input and any other advice. I am hardly technical or mechanically inclined so this is a huge help!
 

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Okay, allow me to check my manuals tonight and I will give you some guidance on this troubleshooting. It will take a while though since I expect to be back home by 10:00 PM CST
 

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thegazelle,

Let's start with the fuse of the navigation system for the anti-theft security, fuse No.5 (10 A) from the under-dash fuse/relay box. If fuse is good, check for open wires, lose connector, or poor ground on nav unit connector C (8 Pins) terminals/pins No.1, 2, and 3. Connector C is the small connector with 8-pins but 7-wires, pin No.3 pin is not wired.

- Pin No.1 white is permanent +B (12VDC) power for anti-theft system supplied by fuse No.5. Also, check fuse No.7 which is also +B to the nav unit display. The schematic refers to both fuses as supply power to the nav unit.
- Pin No.2 purple is ACC power (from ignition) supplied from fuse No.32.
- Pin No.4 black is ground (G605).

Verify ground continuity to G605 and voltages +B and ACC at connector C behind the nav unit. If all circuits are OK, replace nav unit. If not, repair any damaged circuit. Your best bet is fuse No.5 is blown.

PRG
 

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Discussion Starter #6
Thanks...I will check fuse 5 shortly.

So...any idea why it doesn't ask for a code when I turn the key to POSITION II? It just has the OK acknowledgement But then when I turn the engine on fully it asks every time.
 

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I will check the manual and read about it. What I read is it should ask for code in position ON. I have not seen the switch if they are the same position or not.
 

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Discussion Starter #8
Thanks again for your help, much appreciated. OK I tried to change out fuse 5. I took out the old one and it looked fine (inside wire not broken) but I changed it out anyway. It made no difference - it asks me for the nav code and the radio code on the next engine start; however, after a subsequent start, the nav code was asked for again, but not the radio code. So changing the fuse did not yield any difference.

For fuse 7, though, it says in the manual it is for the moonroof and interior light, both of which work fine. So it can't be that one.

I did check fuse 32, and it too is good.

Tomorrow, I shall try unplugging and plugging in the wires in the back of the nav unit.
 

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the nav unit is located under the driver's seat. Connector C is al the left side of the rear of the nav unit.

Per service manual, the code is asked when the key is turned to ON (II). It does not specify after or before engine is started.

Every fuse supplies voltage to more than one device. So, the next issue is bad wiring or poor ground to the nav unit.

1. Measure voltage between pin No. 1 and body ground. That is your theft protection voltage. You should see more than 12 VDC
2. Measure voltage between pin No. 4 and body ground. You should see less than 0.5 VDC. G605 is a ground connector with multiple black wires under front passenger's seat (front side of seat). There is another ground connection at the rear side of the front passenger's seat that is called G606.
 

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Discussion Starter #10
All right - for reasons I can neither explain nor fathom, after yesterday's fuse checking, I just shut off the car and went inside, as it was night. I didn't change any fuses. I did pull and check the ones noted in the previous message, and all fuses were good. This morning, I load the kids in the car, start it and get the usual asking for the navi code. I enter it and I see the "your car has lost power and it will take a few minutes to regain GPS signal", etc. It took about 8 minutes, regained the signal as I was driving and I thought nothing of it as I headed to my parents' place with the kids. After I dropped the kids off I had to go out to the bank. I turned on the car and it did not ask for the navi code, but went straight to the acknowledgement screen. I didn't really think much of it until I got to the bank when I realized I did not have to enter the code. When I went back to the car, I restarted it. No code asked. Weird. When I left my parents place later to go home, no code asked. I am home now and inbetween watching the hockey game, and the kids are sleeping, I thought I'd go back to the car and restart it since it's been a few hours. Once again, it did not ask for the navi code. It looks like the problem resolved itself. The big question is...how? I did not change any fuses or do anything else.
 

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I would say this, it was a RESET. The fuses were good. So, by removing the fuses the unit went into a complete shutdown. Then, you re-installed the fuses. That was a good power-up and internal boot-up too. Then, it asked for the code and you entered the code as expected. Now, all is good as it should. There you go, it was a HARD or COLD RESET. Simple.

I am glad you got it right now. Until the next one and enjoy your MDX. You will like it.
 

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Discussion Starter #12
Thank you PRGonzalez. I will try it once more this morning before church to see if it stays in this condition. With a brand new battery, the diagnostics checking out for all units and modules, and up to the date software, I was stumped. Regardless, you provided great insight and your troubleshooting steps helped to get to this result. At any rate, as promised, aside from public acknowledgement for your awesome willingness to help (thank you!) - send me your email address by PM please. Thanks!

-jeremy
 

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Discussion Starter #13
Well, we are right about to go to church and I thought I'd start the car. No Nav code needed! So I think it is now permanently fixed! Send me your email address by PM when you get a chance...thanks again!
 

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Hey guys, I'm a new user to this site. I own a 2008 Mdx with the tech package. My Gps will not work at all. I have reset fuse number 5 and fuse number 32. Still my GPS is blank nothing going on. Number 5 seemed to reset the radio which was already working fine. I just had to enter the code. I have been able to get the dvd out of the player under the drivers site. I dont think that it is getting any power at all. Any suggestions Thanks
 
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