Well, it was a heck of a morning. Backed the boat down into the water, tied it to the dock, got back into the Pathfinder, put it in drive and NOTHING, no revving, no throttle response, nothing. Put back into park and revs fine. Tried all drive gears and nothing.

Luckily there was a line of nice full size trucks waiting to launch their boats. One guy had a tow strap and within a few mins I was up and out. He did think it looked like the truck was trying to move, but there was no throttle response.

Anyway, the guy pulls me way up and out of the way. I turned off the pathfinder to park it for a min and think of a plan. Go to start it again and the battery is dead.

Eventually I get the pathfinder and my boat back home. I was able to jumpstart the pathfinder and measure the voltage across the battery to be 11.5V. So, I am thinking initially its a bad alternator.

For a looooong time, like many years, upon start up there was a good squeal under the hood, but this spring it magically went away! On the way to the boat ramp this AM, something did sound a bit different under the hood, a bit of a whining sound.

So I am now thinking that the belt, tensioner and pulley should be replaced before jumping to the alternator. I am thinking that a bad tensioner and belt could be causing the alternator to slip, causing the lower voltage. (Note that I am pretending that these vehicles don't have transmission issues)

MY big question is, before I go any further, would a bad serpentine belt/tensioner and/or an under powered alternator cause the transmission/engine to not be able to drive. Again, the engine revved up in neutral and park, but the throttle was totally unresponsive in drive.

A bit of background on the pathfinder. Its a 2005 LE, Bought it used in 2014 with 70k miles. Its now at 140000k miles. Its gotten a lot less use in the last year, relegated to boat towing duties. I have done a lot of work over the years (lurking on this message board since 2016) most of the usual suspects: Radiator bypass, crankshaft position sensor, CATs O2 sensor, exhaust, shocks/struts, wheel bearings, axles, etc... I did have to do the transmission oil pan this summer and everything was looking good there. BUT, I have never touched the serpentine belt/tensioner

So, if anybody has any ideas or input, I would greatly appreciate it. I have had fun with this pathfinder over the last few years but its nearing its end. My minivan is more than capable enough to two my small fishing boat, but I have a hard time letting go of things. Part of me wants to hold onto it, the frame and undercarriage are in great shape, minimal rust, and then lift it when my oldest son gets older.

If frame and under carriage are in good shape its ALWAYS worth saving the vehicle.
Mid size body on frame SUVs are gems and are getting harder to find outside of stupid money.

Even though your vehicle dates all the way back to 2005 it was the first year of a design that is functionally identical to some new but expensive vehicles currently still produced and sold for big $$ such as the current 4runner
I'll let other more sage members comment on your tech questions for you.

On vehicles which have the "smart" charging system controlled by the IPDM (as yours does), a very crappy battery can cause exactly the symptoms you describe without the alternator being bad. The wife and I had an identical experience on a recent Nashville trip, the 6-year-old Walmart battery in our Altima gave up the ghost on the way out there. Coupled with a tiny bit of resistance in the Throttle Body drive circuit, the car began intermittently not taking the gas in drive because the TB motor was low on juice. The "smart" system did the usual dumb stuff and didn't ramp up the charge rate. The upshot is, a new battery fixed all of it. I cleaned up some contacts at the IPDM and TB on our return, but it didn't really need it. We had zero issues on the return trip, even before I did that.

I've seen similar behavior in some customer vehicles over the years, too. The bottom line is, if your battery has seen better days, try that first.

just to answer. The truck can drive without the belt on, I've done it around the block.

If battery is older that 5 years, I would suggest replacing it.
The car battery is the only thing people will let "die" rather than replace it at suggested intervals on cars.


Kirkland/Costco and Walmart is best (warranty/price)


I'm getting close to the magical 321868.8 km mark myself on my '05.

VStar650CL wrote: ↑

Sun Sep 18, 2022 7:22 am

On vehicles which have the "smart" charging system controlled by the IPDM (as yours does), a very crappy battery can cause exactly the symptoms you describe without the alternator being bad.

So if the IPDM sees a lousy battery it will throttle down the alternator voltage? I was thinking belt/alternator largely because of the alternator voltage being 11.5V rather than the 14.3V or so it usually is.

TooMuchControl wrote: ↑

Sun Sep 18, 2022 9:03 pm

just to answer. The truck can drive without the belt on, I've done it around the block.

If battery is older that 5 years, I would suggest replacing it.
The car battery is the only thing people will let "die" rather than replace it at suggested intervals on cars.


Kirkland/Costco and Walmart is best (warranty/price)


I'm getting close to the magical 321868.8 km mark myself on my '05.

You know, the battery is a four year old EverStart from Walmart (my go to). I discounted the battery as the culprit largely because last week, a 10 month old battery on my Minivan failed with a bad cell, which I only figured out after much hassle and an unnecessary starter swap.

What are the chances of two batteries failing in the same week!?!??

Ha..

I will report back when I figure out more.

Thanks folks!

captngrif wrote: ↑

Mon Sep 19, 2022 6:38 pm

VStar650CL wrote: ↑

Sun Sep 18, 2022 7:22 am

On vehicles which have the "smart" charging system controlled by the IPDM (as yours does), a very crappy battery can cause exactly the symptoms you describe without the alternator being bad.

So if the IPDM sees a lousy battery it will throttle down the alternator voltage? I was thinking belt/alternator largely because of the alternator voltage being 11.5V rather than the 14.3V or so it usually is.

No, but with a crappy battery it doesn't need to throttle-down the alternator, just fail to properly throttle it up. Goofyware does goofy stuff when presented with goofy circumstances the programmer didn't account for.

Last time I checked you could still take batteries and alternators in to the auto store and get them tested for free. Could be worth doing.

Update:

I charged the battery over a couple of days, measured about 12.33V once fully charged. Fired her up and the voltage across the battery dropped to about 11.99-12.00V.

Truck sat for a week, measured the battery this afternoon, 12.26V Went ahead with the belt, tensioner, and pully change. The pulley bearing was shot, and the belt was aged. Tensioner seemed ok.

Fired her up and same situation, voltage dropped to 12.00V.

I would think that charging the battery might trick the smart charging system into thinking the battery was ok. But who knows.

Guess I will try a new battery, 4 years old is ok I guess... If it was 5 years old I'd feel better about it. Kind of feel like I am throwing money at the problem.

captngrif wrote: ↑

Sun Oct 02, 2022 3:29 pm

Update:

I charged the battery over a couple of days, measured about 12.33V once fully charged. Fired her up and the voltage across the battery dropped to about 11.99-12.00V.

Truck sat for a week, measured the battery this afternoon, 12.26V Went ahead with the belt, tensioner, and pully change. The pulley bearing was shot, and the belt was aged. Tensioner seemed ok.

Fired her up and same situation, voltage dropped to 12.00V.

I would think that charging the battery might trick the smart charging system into thinking the battery was ok. But who knows.

Guess I will try a new battery, 4 years old is ok I guess... If it was 5 years old I'd feel better about it. Kind of feel like I am throwing money at the problem.

Is 12v what you got while it was running? Did you try revving it to about 2/2.5k rpm and testing while reved? I would expect to see 14-14.5 volts. You may have a bad connection or alternator or battery.

I would start by testing your battery with a battery tester to see if it’s any good. Voltage test alone is insufficient though it does look like it may be a bad battery, a voltage test alone is insufficient to make that determination at that voltage level.

That 12.33V on a full charge isn't healthy. 12.4V is the minimum for a healthy float voltage, 12.6 is "new battery" spec. I'm afraid you're doing exactly what @TooMuchControl suggested, replacing everything except the guilty party.

AS_The_Crow_Flys wrote: ↑

Sun Oct 02, 2022 5:21 pm

captngrif wrote: ↑

Sun Oct 02, 2022 3:29 pm

Update:

I charged the battery over a couple of days, measured about 12.33V once fully charged. Fired her up and the voltage across the battery dropped to about 11.99-12.00V.

Truck sat for a week, measured the battery this afternoon, 12.26V Went ahead with the belt, tensioner, and pully change. The pulley bearing was shot, and the belt was aged. Tensioner seemed ok.

Fired her up and same situation, voltage dropped to 12.00V.

I would think that charging the battery might trick the smart charging system into thinking the battery was ok. But who knows.

Guess I will try a new battery, 4 years old is ok I guess... If it was 5 years old I'd feel better about it. Kind of feel like I am throwing money at the problem.

Is 12v what you got while it was running? Did you try revving it to about 2/2.5k rpm and testing while reved? I would expect to see 14-14.5 volts. You may have a bad connection or alternator or battery.

I would start by testing your battery with a battery tester to see if it’s any good. Voltage test alone is insufficient though it does look like it may be a bad battery, a voltage test alone is insufficient to make that determination at that voltage level.

The 12V or less, is what I am reading while its running, revving doesn't move the voltage at all.

Clearly the alternator is not producing the proper voltage, but some are saying its the bad battery causing the charging system to misbehave.

We will see, I am grabbing a new battery tomorrow. Ordered an alternator, will be in the store Wednesday, can cancel the order if battery does the trick.

Thanks everybody!

One can kill the other, both ways. The battery is definitely trashed with a 12.3V float. Before you replace the alternator, check the field fuse. If it's blown, it's a telling clue that the alternator went bad and chronic undercharging probably depleted the battery. If it isn't, check your charge voltage after swapping alternators and make sure it isn't overcharging. That will also kill both. If the new one runs higher than about 14.5V then the culprit will be the battery current sensor, so either replace it or clip the smart wire.

VStar650CL wrote: ↑

Sun Oct 02, 2022 6:21 pm

One can kill the other, both ways. The battery is definitely trashed with a 12.3V float. Before you replace the alternator, check the field fuse. If it's blown, it's a telling clue that the alternator went bad and chronic undercharging probably depleted the battery. If it isn't, check your charge voltage after swapping alternators and make sure it isn't overcharging. That will also kill both. If the new one runs higher than about 14.5V then the culprit will be the battery current sensor, so either replace it or clip the smart wire.

Good info, I will take a look at the fuse tomorrow and report back.

New battery is in, essentially measuring the battery voltage 12.5V when running.

Got the new alternator in, fired it up and voltage measured 14.40 at the battery everything looked good, let it idle for a while while I pumped up the tires and such.

Went for a drive, noticed the voltage reading on the dash wasn't as high as it was at first. Came home and voltage at battery measuring 13.33V at idle.

Going to take a closer look at all connections sometime today. I seriously hope I did not get a lousy alternator from NAPA, unfortunately it wouldn't be the first time this has happened to me over the years.

captngrif wrote: ↑

Mon Oct 10, 2022 7:23 am

Got the new alternator in, fired it up and voltage measured 14.40 at the battery everything looked good, let it idle for a while while I pumped up the tires and such.

Went for a drive, noticed the voltage reading on the dash wasn't as high as it was at first. Came home and voltage at battery measuring 13.33V at idle.

The 13.3V is about right once the battery is topped up. Once it stops sucking charge and the current sensor reading drops, the smartwork will reduce the charge level. They shouldn't go under 13.0V or stay in the low 13's constantly even when loads are turned on, that's a sign of a bad current sensor.