I am looking to see if all newer 2021 Frontiers have this problem.
When driving, the computer sometimes will read 11.6v and stays like that for a full 30 min trip.
When idling it sometimes goes up to 14v and sometimes when it's moving I get 13.5 So it's random.
But my concern is when I'm driving for 30 mins and shut the truck off the battery is at 11.7 The dealer says it passed all test and that's normal to save on gas. My bigger concern is with a battery sitting at 11.7 for 4 days it's killing the battery, I'm on my 3rd one.
I have a ScanGauge - SG2 that I use to monitor transmission temps and battery voltage. That's how I'm seeing all this while driving. I'm sure someone on here can monitor voltage while driving.

The gen3 Frontiers all have the same setup as the late model Rogues, the alternator has a LIN link with the ECM. That makes it impossible to "tweak" it like the PWM-controlled alternators in some earlier models. The only thing you can try is unplugging the Battery Current Sensor located on the battery ground lug. That may light the MIL but I think not, since the FSM doesn't show any failsafe for the P155x DTC's. Unplugging it should force the ECM to govern charge according to voltage and not demand. I'll be interested to know if it works and if it lights the MIL or not.

So what I found is a wire in the ipdm needs to be removed and that will turn the alternator back into a dummy alternator. So now I need to find the diagram and pin out diagram for the 2021 frontier. If you have that info or know where I can get it please let me know. Here is a video explaining it all https://www.youtube.com/watch?v=P9C5-OkxrJU&t=4s

That doesn't apply to a D41 Frontier. I already explained that your alternator is LIN-controlled and not PWM, and it connects to the ECM and not the IPDM. Cut the comm wire and you'll watch your dash light up like a Christmas tree.

VStar650CL wrote: ↑

Wed Sep 20, 2023 7:02 pm

That doesn't apply to a D41 Frontier. I already explained that your alternator is LIN-controlled and not PWM, and it connects to the ECM and not the IPDM. Cut the comm wire and you'll watch your dash light up like a Christmas tree.

LOL you helped others with the same problem, haven't you? I just read a post about the same thing for the 2nd gen and up with the "light up like a Christmas tree" comment lol
So nothing I can do at all? If I called Nissan would they have a way of turning the smart charging system off? Im sick of plugging the battery in every other day.
If the wire was cut and the warning came on, would that be the worst of it?
And is the 2021 a gen 2 or 3? I will try the plug again and drive around. The last time I unplugged it I just watched it for a min and saw no change so I plugged it back in.

I just drove with the harness unplugged and that got it up to 13.5 Now what if I added a resistor to the wire that reads the voltage to make the system think the battery voltage is lower than it really is, would that work?

I'm done here. If you don't know the difference between LIN and PWM and don't want to find out, I'm not going to explain further. Voltage on a LIN signal wire has absolutely nothing to do with it.

VStar650CL wrote: ↑

Thu Sep 21, 2023 4:32 am

I'm done here. If you don't know the difference between LIN and PWM and don't want to find out, I'm not going to explain further. Voltage on a LIN signal wire has absolutely nothing to do with it.

You’re right I really do not know the difference between the two, but I will start doing some research on it. I also appreciate the info that you have given me. It definitely has saved me a lot of time. For now I suppose I will just leave the connector unplugged since it is giving me a higher voltage than what I had before.

I'll save you some research then.

PWM is a 1-way interface, the duty cycle (the amount of time spent "high" versus the time spent at 0V) determines how fast or hard a device runs. It's actually a series of pulses, but because they're very rapid, they look to your voltmeter like a variable voltage. Because it's 1-way and because the "failsafe" is for the alternator to internally regulate, snipping the wire gives control to the alternator without the driving device (the IPDM on Nissans) being any the wiser, so you don't get any codes.

LIN stands for Local IntraNet and it's a 2-way interface. It's usually what we call a "bit-bang" employing one of the various RS communication formats, archetypically RS232. The master transmits commands which the slave then acknowledges or verifies. That's why you can't simply f#ck with the LIN wire, because the ECM is expecting a reply. It will know instantly that the alternator is offline and light the generator and brake lamps in response, and possibly also light the MIL.

Could Nissan change how it works with a software push?
Also what’s the best work around to keep the battery healthy? I have a trickle charger mounted under the hood now. I just don’t drive it everyday and when I do it’s only 2 miles or less.
Thanks for the break down

rhconcepts wrote: ↑

Thu Sep 21, 2023 7:16 pm

Could Nissan change how it works with a software push?

They could but they didn't. It isn't configurable, you're stuck with whatever is in the ECM firmware. A professional tuner might be able to change the parameters but I don't know if anybody is tuning VQ38's yet, they're still brand new.

rhconcepts wrote: ↑

Thu Sep 21, 2023 7:16 pm

Also what’s the best work around to keep the battery healthy? I have a trickle charger mounted under the hood now. I just don’t drive it everyday and when I do it’s only 2 miles or less.

A trickle charger should work fine, that's a good idea for any vehicle that isn't driven every day or typically makes lots of short trips. As it happens I have a '22 in my bay right now that I can take some measurements on, I'm going to see if the current sensor can be "dummied" to make the ECM think the load is high all the time and provoke maximum output. That would be the best fix if it works.

Well, I think I have a solution for this, but it will take a couple of resistors and a little rewiring. The sensor is a Hall type with a push-pull output, it reads 2.5V at neutral, higher when the battery is taking current and lower when it's discharging current. So feeding the ECM a fixed load signal of about 2.2V should fool it into thinking there's a constant discharge and make it ramp up the charge rate without causing any codes. However, because it's push-pull, you can't just bias it with a pull-down resistor. The easiest way to overcome it is with a resistor divider using a 1.3 Kohm connected to the 5V supply (Red) and a 1 Kohm connected to ground (Black). Connect the two resistors together in the middle, snip the data wire (Blue), and connect the end going to the ECM to the junction of the two resistors. That will feed the ECM a constant 2.2V regardless of the actual load.

OK that doesn’t sound terrible but I’m more of a electrical guy rather than a mechanic. Any chance you could show a video or photos of how you’re connecting them and where that wire is?
Otherwise, it’s still sitting at 13.6 with that connector unplugged from the negative side of the battery. And it hasn’t generated any codes with that being disconnected.

If there are no codes then I'd say call it good, but I'm not sure why there aren't. You should be getting some sort of P155x and a temperature sensor code as well, so that's a little weird. I'll make up a diagram when I get a chance, I'm a little pressed for time today.