Please help point me in the right direction to troubleshoot the following problem.

I just notice an odd behavior with my 2008 M35x. The ignition button automatically jumped from ACC to LOCK without any interventions. I first noticed it because I was listening to music in ACC mode. The whole AV loss power and shut off. I thought maybe my battery went dead so I checked the battery voltage and it's fine then I checked the ignition button and realized it was in the LOCK or OFF position. So I thought maybe something was wrong with the AV. I tried again a few more times and it did it whether I play music from the CD player, the Compact Flash card or the built-in storage drive. So, I turned the AV system off then push the button to switch to ACC again thinking that maybe the AV system was drawing too much power causing the car to turn it OFF or LOCK. After a few minutes the ignition button switched to LOCK again. I kept trying it with all the doors closed and everything electronics related turned off, sometimes it took a few minutes to switched from ACC to LOCK, other times it did it as soon as I turn to ACC. It switched to LOCK even faster if the push button is in ON mode. The car started and drive without issues. I am a a loss on this so any help will be greatly appreciated.

Thanks and regards,
Sam

That sounds too erratic for the Power Saver to be causing it, and it can't be a weak battery if it starts okay. The AV can't cause it either, the button and illumination are both wired to the BCM and not the AV. Sounds more like the button is "falsing" or the accessory relay is dropping out. The button input to the BCM is a simple pulled-up grounding circuit, so try disconnecting the button while it's in ACC and see if the radio stays on until the PS kills it. If so, it's a bad button.

Thank you for your suggestion,Vstar, just one question/clarification. When you said ...”until the PS kills it” did you mean when the battery dies or is there some built-in logic’s that can sense the button is disconnected and turns off everything?

Thanks again. I will try what you’d suggested as soon as I get home
Regards

There's a Power Saver function in virtually every late model N/I product that will kill the head/parking lights, dome lamps and accessories after 20~30 minutes to save the battery. Some also have the ability to kill it quicker if the battery is very weak. The BCM is in charge of both functions. If the key is in ACC or RUN, most (but not all) will give a warning on the dash that they're about to shut down.

Update: I disconnected the ignition button and shorted terminal 1 and 4 on the harness side to mimic the push button PUSH action, the car behaves exactly the same. I also switched the push button with the one from my Maxima which is exactly the same as the one from the Infiniti but the problems continues so I don't think the push button switch is the problem. One thing I notice is the fan blower motor also shut off when the car automatically switched from ACC to LOCK . The instrument panel, AV, A/C, blower fan, and the screen all turned off regardless if the engine was running or not. The only difference is if the car is running, the engine won't shut-off whether it was in park or when I was driving it. The car drives just fine without any engine issues, no loss power or stalled. I traced the circuitry and it looks like both the ACC and Blower fan relay coils are fed by the same power line coming out of the PDU. I checked continuity between the PDU harness and the harness at the fuse block and everything checked out. There is also voltage at the PDU terminal that fed the relays' coils so I am at a total loss on what's going on. I went through the Infiniti PG FSM as far as measuring the voltages and continuity and everything seems fine. I also took the car to the shops and auto parts stores to read fault codes and no codes were present. The shops had no idea and recommend I get some one with electrical expertise to troubleshoot. I am an electrical engineer with 30+ years experience in power distributions on low, high, and extra high voltages but that doesn't help. I talked with the Infiniti dealer and they wanted to charge around $250.00 just to hook up their diagnostic tool and see what they can find. I am sure they will "recommend" replacing every modules one by one until everything in the car is new and hopefully the problems will go away. Dealer and service shops don't really troubleshoot anything any more; they are just parts swappers. Please let me know if there are anything else I could check. I have other cars to use so this one will be sitting in the garage until I can figure out what's wrong with it. It's a personal challenge for me now. I truly appreciate any help or pointer.
Regards,
Sam

The only way to trace this may be to find out what the BCM is responding to, and that will mean a high-end scanner like the Consult3+ that can read all the BCM inputs. Short of that, one thing I'd suggest is making sure all the door switches are good, since the PS and retained power (RAP) logic is all tied up with the doors. Checking the Ignition supply to the BCM would also be a good idea, since transitions on that line can cause a lot of weird behaviors. On most N/I models the BCM "commands" the ignition relay, but the IPDM actually drives it. The "detente" switch in the shift knob can also cause weird stuff.

Update: After months of tearing things apart and check all the connections, I still couldn't figure out what went wrong. I measured the voltage signals coming out of the BCM according to FSM's BCS and BL they are all good. The car has no engine or any other issues; just the ignition switch automatically go from ACC or ON to LOCK without any intervention. I can drive the car for an hour or longer without issues except the instrument panel and the AC control and blower fan intermittently loss electrical signal i.e. they keep turning OFF and ON randomly. Sometime, the AV resets itself and started playing music from the CD-ROM drive. I suspect the PDU is having problems because the Accessory and Blower relay's coils are fed from the same terminal 16 of the PDU and if terminal 16 of the PDU is losing power that would explain those two relay contacts to open and close randomly causing the instrument panel and the AC fan blower to stop working. If I disconnected harness M31 from the PDU then the ignition switch work properly (i.e. not randomly switched from ACC or ON to LOCK). However, I won't be able to start the engine or turning on the AV since the got no output power from the PDU. I also jumped terminal 16 and 18 of the M31 harness to give them 12V but it gave me the same behaviors as before.

I'm wondering if the PDU is shot or if it expected signals from some other modules in order for it to function properly. I checked the signal voltages on terminal 4, 5, and 8 on the M30 connector of the PDU and they seem okay. Is there anything else I could check? Should I just get another PDU and see if that would fix my problems? Any pointers or guidance will be greatly appreciated.

Regards,
Sam

Yep, the PDU sounds likely. On your ride all the stuff that's dropping out runs off the PDU ignition output except the blower and AV, but the blower would drop out indirectly if the HVAC's ignition supply dropped out and the AV would likely cycle or drop out even if the accessory supply stayed up. If it was a problem on the supply side of the PDU then the engine would likely be affected too. If it was a wiring problem on the output side then it's unlikely that multiple fused circuits would be affected, unless maybe from a bad main wire between the PDU and the inside fusebox. I'd think the latter would cause more of a "dropping out over bumps" thing than just going out randomly. So a crippled or dying PDU sounds like the most likely culprit.

Thank you VStar650CL for confirming my suspicion on the PDU. I'll look for a replacement PDU and will update after I switched out the existing one. Hopefully, that's it. I hate to throw out a working car for this issue but it's not safe to drive it without reliable information for speed, engine temperature, fuel level, heating/AC, etc... Please wish me luck.
Thanks again and best regards,
Sam

Update. I replaced the PDU and the issues stays the same but now none of my ikey fobs work. They can’t lock or unlock the car. I also got a brand new AGM battery but that didn’t help either. The car acts like it doesn’t recognizes any of the key fobs even if I inserted it in the slot. If I pushed the start button the dash displays the key symbol and the brake pedal but nothing comes one. I couldn’t even turn on ACC, ON or start the car. If I left the key fob in the slot and opened the driver side door then the car dings letting me know the key fob is still in the car but the dinging stoped when I removed the fob from the slot even if I left it on the seat or cup holder. I could use the mechanical key to lock the car with the key fob still inside the car but outside of the slot. It’s weird. I took the BCM out and bench tested it, everything checked out okay. What would possibly be the problem now. For a few months I could somehow managed to start the car once in awhile then shorted the ACC and Blower relays output and the dash, AV, heating and air conditioning, etc.. for hours without issues. I drove it for 4 hours without any problems. Just make sure I don’t shut the engine off otherwise I might not be able to start it again and be stranded. I even took the car to the shop and the Nissan dealer to read error code while the engine was running and there weren’t any error codes. Now the car won’t do anything at all; won’t turn on ACC or start. Please help

Thanks in advanced

Btw, I forgot to mention that I measured the voltage supply to the ACC and Blower relays’ coils and it fluctuate between 0 and 12v. That’s why it causing the contacts to open thus causing the dashboard, AV, and HVAC to cut in and out therefore I just shorted contacts and everything was working when the engine runs

The FSM doesn't show the PDU needing any configuration or programming, so if you're sure it's a good unit, then something else must have happened. I'd start by checking all the fusible links, there's at least one each that can bring down the BCM or IPDM and basically disable the whole car.

Update: I rechecked all fuses and fusible links, everything checked out okay. The car has electrical power to everything that I checked. The headlights can turn on/off, the security light is blinking red, the dome light is turned on when any door is opened, brake lights and signal lights all work, etc… I can use the mechanical key to lock and unlock the door and rolled down the windows but then I couldn’t roll the windows up because I couldn’t switch the ignition button to ON. It wouldn’t go toACC either since it Seem to have no power at the push button. No indicator lights on the button lit up. However if I disconnected the “control wires connector” the one with tiny wires from the PDU then I can roll up the windows and the AV screen come on with proper information such as outside temperature or estimated distance remaining based on the remaining fuel in the tank.

I am at a loss on what to do next as I had stated in my previous osts, the voltage at the ACC and Blower relay coils is on and off between 0-12V and that maybe preventing the push button from operating or receiving electricity. Can I run a 12v line from another source or directly from the battery to the fuse/JB to give the relay coils the voltage they need to keep the contacts stay close so I can see if I can get into ACC orON modes. I shorted the contact terminals but it doesn’t work because the system seems to look for some kind of response from the relays. I also got two replacement relays but they acted the same way; the relYs’contacts closed and opened rapidly causing almost continuous clicking sound.
Thanks in advance for any help or guidance.
Sam

Have you looked at the iKey unit? That controls power to the push button start and also receives the radio signals from the fob so you dont have remote lock or unlock, but the mechanical key still works. It is sounding very similar to my problems with a dead iKey to me.
topic628851.html

I’ve suspected it’s the iKey module too but I don’t know how I can really test it before sinking money into it especially it will require reprogramming the fobs which could only be done at the dealer for it to work. Can I buy a used iKey module from a junkyard and slap it in to see if that works? Would an iKey module from a 2014 Maxima works in my 2008 M35x?

Thanks in advance for your help

You could check the actual voltage on the wires going to the push button and the doghouse. If they have no voltage then the iKey isnt passing it through properly. Not the most perfect test, as you may get voltage even if the iKey is broken. But if you dont get voltage, and all fuses check out good, and you do have voltage at the entrance wires of the iKey then you can probably say with certainty that the module is the culprit.

When you place the new working iKey in the car the ignition button will light up if that was the issue, you just won't be able to do anything and get a no key ID error.
I was able to get mine used for $75. I just did a quick search but didnt find anything on Ebay for more used ones

SamW wrote: ↑

Wed Jun 01, 2022 8:21 am

Can I buy a used iKey module from a junkyard and slap it in to see if that works? Would an iKey module from a 2014 Maxima works in my 2008 M35x?

Good idea to search for one from the junkyard. The 7th Gen Maxima (2009-2015) does not use an IKey module, however.

Please pardon my ignorance; I don’t get what you meant by “You could check the actual voltage on the wires going to the push button and the doghouse”. What is the doghouse?
Thanks

The doghouse is the small port to the bottom left of the steering wheel where you can slot your keyfob remote into. Often this will allow the key to work to start the car when it otherwise isnt detecting the key, usually due to low battery.

If you can use a voltmeter or test light to check the power wires going to the doghouse and push button, and there is no voltage on any of them then the iKey is most likely dead if you already ruled out a fuse not being a problem. There could be a wiring issue as well but that would seem less likely to me than a dead module.

Thank EniGmA1987. Now I know what a doghouse is and it's not the place that I have to be in when I misbehaved

As I stated in my previous update, when I inserted the keyfob in the slot and opened the driver door, I can get the ding sound to tell me that the keyfob is inside the car and I could not lock the car so it looks like there is power to the doghouse. However, I will verify it with a multimeter to be 100% sure. Also, with the keyfob in the slot, I sometime got the LOCK indicator light on the push start button lit up for a fraction of a second but not long enough for me to push the button to turn on ACC or ON mode. Once in a blue moon, if I caught it just right, I can turn on ACC but it immediately turned off back to LOCK and then dark button again. I traced it back to the ACC relay's coil supply voltage being cut-off. That was why I asked if I can feed the relay's coil with 12v from the battery or somewhere else to see if I can generate a different response without damaging other components. One time, I took out the push start button and shorted terminal 1 to 4 inside the connector to simulate the push action and I accidentally shorted one other pin to ground and blew out fuse #22 so I know there is power to the push button. However, I will verify that there is voltage to the push button to be sure.

Before all of these problems, the only issue I had with the car is the dashboard would intermittently turn ON/OFF by itself for a brief 3-5 seconds while I was driving but I had no problems with starting the car or listening to the AV in ACC mode, so I thought there was a lose connection some where. I practically took the whole front in the cabin apart and checked every connectors in the engine bay as well for lose wires but found nothing. Could that be an indicator that the iKey control module was on its way out? During that time, I made several 1200+ trips and driving the car for months around town without any problems with lock/unlock and starting/stopping the car no matter what the weather was, from subzero to 100 degrees. Just one day out of the blue everything quit. Since then I'd replaced the car battery twice, the keyfob batteries multiple times, push start button, PDU and all the fuses inside the cabin and in the IPDM. The shops could read any error codes when I drove the it to the shop and they told me since the check engine light is not on, there wouldn't be any errors. I also performed the IPDM Auto Active Test and everything passed which tells me the BCM and the IPDM are functioning correctly. Now the car is completely dead at the push button so I couldn't do any testing. The only logical choice left is the iKey Control module which the dealer will want big money to just install one to verify the current one is bad which I'm afraid of wasting the money if that doesn't fix my car.

Thanks in advanced for any ideas, information or guidance you and others in the forum can provide
Regards,
Sam

Update: I verified that I have voltage at the push button start and the dog house. While troubleshooting, I noticed that if I just connect the power connector (the one with all the thick wires) of the PDU, I will get the dashboard, AV, and the screen to come on and stay on for how ever long I let it but the push start button still not working. The dashboard, AV, and the screen turned off when I connect the other connector to the PDU. Can anyone tell me what that means?

All other electrical related components work a they suppose to. Headlights signal lights, power windows, power door locks, wiper blades, etc… all wok. The only thing that won’t work are the buttons on the kepfobs and the start/stop push button. As I’d mentioned previously, if I insert the key fob into the doghouse, the chime dings when I opened the driver door and I couldn’t use the switch on the door to lock the vehicle so it looks like the key fob is recognized by the car. I’d replaced the battery in the fob with brand new one about a dozen times already so I’m sure at least one of those batteries is good
I’ve been looking all over town for a used iKey control module but couldn’t find any. I even try to order one online but it never came. Please let me know if ther are anything else I could do to troubleshoot.
Thanks in advance for for your help

Update:
I just got a used iKey control module locally and installed it. I got the push start button to light up with the replacement unit now. What's my next steps? Do I have to tow the car to the dealer to reprogram all my key fobs to work with the new used iKey control module or I can get a mobile locksmith to come to my home and do it? Is there any tools that I could buy and do it myself? Any help and/or guidance will be greatly appreciated.
Regards,
Sam W.

Most smithies will have the stuff to do an '08 in your driveway. It's mostly the '13-ups with long rolling codes that they sometimes have problems with.

Thank you for a quick reply. Do you have any ideas on the costs for a locksmith to do the programming? I’m thinking if it a few hundred dollars then I can probably use that to buy myself a good scanner with key programming capability so I can use the diagnostic tools for my other vehicles too
Thanks again and best regards

If it's a few hundred dollars then you might as well tow it to the dealer. Most charge an hour labor for key programming, some charge less. I'd expect a smithy to be cheaper than that, but call around. Just like repair shops, some charge much more than others.

Update:
I called the local Infiniti dealer and explained to them about my situations and I need to get an estimate on how much it will cost for the job. They asked me all kinds of questions but I was shocked at what the "service advisor" told me. He said, he never heard of the Intelligent Key Control module before and doesn't even know where it is. I told him where he can find it then he told me to hold while he consult with other advisors and techs. He cam back 15 minutes later and told me they never had to replace a key control module in their shop before. Then he asked me how do I know the one in my car is bad so I explained to him what I've done to come to that conclusion. After that he said I'll have to bring the car to the dealer so they can perform diagnostic on it to be sure. I told him, the car is dead because none of my key fobs works with the original module or the new one. Then he told me to tow it to the dealer and it will take them minimum 3 hours to perform diagnostic at $150.00 an hour. If they verified what I said is true after their diagnosis then they can program the key fobs for the car but I'll have to buy the fob from them at $400.00 a piece since they can't reuse my existing fobs. After 30+ minutes on the phone with them I hung up and told them I'll be out at least $450.00 before anything is fixed which is not very comforting to know.

I called a dozen local locksmiths, some flatly refused to work with Nissan/Infiniti vehicles. The one said they can gave me estimates between $350.00 - $600.00. The $350 is assuming they come and reprogram the key fobs in less than 30 minutes and no issues otherwise there'll be additional costs and possibly parts.

With that kind of costs, I am thinking of buying a key programmer or an OBD scanner with key programming capability and do the programming myself. I figured it shouldn't be that difficult. Does anyone here have recommendations on which tool I should invest in. I've been reading about XTool, Launch, Autel, and some other cheapy alternatives but I would love if someone with experience with any of the key programming tools can point me to the one that proven working for them, not necessarily with Nissan/Infiniti vehicles but any other makes/models so I can be sure I get a working tool.

Thanks and regards,
Sam

You know, I'm not sure the problem with the new-used I-Key module might not be your fobs. On '07~'08 Altimas the fobs could be re-used with a different BCM, but from '09 up they couldn't, they mated for life. Since Infiniti is the proving ground for most Nissan systems, it wouldn't surprise me if your old fobs are unusable with a different (used) I-Key Unit. I'll try to do some digging tomorrow at the shop if I have time, maybe I can find out.

Thanks VStar650CL for a quick reply. I’m looking forward to hear back from you

The issue is not that insurmountable. First, because you have a used I-Key module your present fob(s) registered to your car is necessary for re-programming. In other words, new fobs would be unavailing. Second, since you're well disposed to having your own key programmer I'd suggest this: OBDSTAR X300 PRO4/MK5/Key Master MINI Auto Key Programmer.
https://www.aliexpress.com/item/1005003 ... 6821%21sea
Ideally, but for the costs, I'd have gone for Autel's IM508, which has additional diagnostic capabilities.
You may watch this for an idea of the procedure
https://www.youtube.com/watch?v=Z_JaYCeOW1o
As for the PIN code, the tool will generate it for you.

@Costee is right. I can't find anything in the documentation indicating that the fobs won't be reprogrammable, so you should be able to re-mate the existing ones to the car. If the dealers and smithies are giving you that big of a runaround, getting your own programming tools might be your best way out.