Ignition button problems

Forum for Infiniti M35 and M45, and Nissan Fuga owners.
SamW
Posts: 18
Joined: Wed Mar 25, 2020 7:22 am
Car: 2008 M35x

Ignition button problems

Postby SamW » Fri Dec 11, 2020 7:33 pm

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


User avatar
VStar650CL
Posts: 2679
Joined: Thu Nov 12, 2020 1:25 pm
Car: 2013 Nissan Altima 2.5 SL
2004 Nissan Altima 2.5 S

Re: Ignition button problems

Postby VStar650CL » Fri Dec 11, 2020 8:00 pm

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.

SamW
Posts: 18
Joined: Wed Mar 25, 2020 7:22 am
Car: 2008 M35x

Re: Ignition button problems

Postby SamW » Sat Dec 12, 2020 3:21 am

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

User avatar
VStar650CL
Posts: 2679
Joined: Thu Nov 12, 2020 1:25 pm
Car: 2013 Nissan Altima 2.5 SL
2004 Nissan Altima 2.5 S

Re: Ignition button problems

Postby VStar650CL » Sat Dec 12, 2020 7:04 am

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.

SamW
Posts: 18
Joined: Wed Mar 25, 2020 7:22 am
Car: 2008 M35x

Re: Ignition button problems

Postby SamW » Sat Aug 21, 2021 5:38 pm

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

User avatar
VStar650CL
Posts: 2679
Joined: Thu Nov 12, 2020 1:25 pm
Car: 2013 Nissan Altima 2.5 SL
2004 Nissan Altima 2.5 S

Re: Ignition button problems

Postby VStar650CL » Sat Aug 21, 2021 8:15 pm

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.


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