Idle Help

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f1racer328

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Do I need to reset the bcm when I replace the battery?
You don't really need to do anything, but if you have a GAP you might as well make sure the car knows the correct battery type and what not.
 

powershift

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It sounds to me like your alternator isn't putting out enough amps. I'd replace that if it isn't already fresh. Or you could measure the amp draw during the problem phase and compare the result with the required amount.
 

RebelYankee

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You may be right. Either battery or alternator is what I'm hoping. I do notice that the volts on the display by the speedo have always shown under 12v. Right now it says 11.4v. Check the battery with a meter and it's 12.2v. Engine off.
 

djkaosone

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You may be right. Either battery or alternator is what I'm hoping. I do notice that the volts on the display by the speedo have always shown under 12v. Right now it says 11.4v. Check the battery with a meter and it's 12.2v. Engine off.
Don't read too much into that. I've been down the rabbit hole with charging. These vehicles are too electrically smart for its own good. The PWM alternator will get signals from the BCM and when working properly it will "SAVE" your battery from overcharging itself by maximizing charge levels up to 90% and NEVER 100%.

Read the live values for the following:
Vehicle battery current - Shows amperage to or from the battery
Vehicle battery state of charge - A percentage state of charge
Vehicle battery voltage - Actual voltage from the battery
Alternator current - Shows amperage from the alternator
Alternator load - A percentage usage from the alternator

I watch these numbers during my travels over months, my drives are typically longer than 30 minutes and could be up to 9 hours.
Vehicle battery current - between -40A to +40A
Vehicle battery state of charge - between 65% to 85%
Vehicle battery voltage - 12.2V to 14.7V
Alternator current - 0A to 100A
Alternator load - 20% to 100%

When my battery state of charge is less than 70% it will max voltage and current at 13.7V at 40A. 70% to 75% voltage and current ranges 13.7V-14.7V at 5A to 20A. Above 75% it float charges and this is very random to me, can be anywhere between 12.2V at 40A, 13.XV at less than 5A, or 14.7V at less than 3A. When it's 85% voltage is at 12.2V-12.6V at negative amperage to discharge the battery back down to 70%.

It actually works out the entire electrical charging system.
 

RebelYankee

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Interesting you bring this up. I just read that you should never charge the battery with the posts as it will bypass the bcm. Also I don't know who put this battery in. So I unhooked the battery and am charging it now. When charged I will let it sit for 1 hour. Then I will hook it up and reset the bcm with the gap tool. I know for a fact that I have charged the battery on this truck the wrong way. Hopefully this will help. I will report back.
 

powershift

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Interesting you bring this up. I just read that you should never charge the battery with the posts as it will bypass the bcm. Also I don't know who put this battery in. So I unhooked the battery and am charging it now. When charged I will let it sit for 1 hour. Then I will hook it up and reset the bcm with the gap tool. I know for a fact that I have charged the battery on this truck the wrong way. Hopefully this will help. I will report back.

Where did you read that you shouldn't charge the battery with the posts? I've been doing that daily lol.
 

RebelYankee

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Right here.

 

powershift

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Right here.

Thanks for the link. Interesting theory. My Land Rover service manual is only for 2009-2011. Maybe the manual for the 2012+ discusses that, I haven't been able to find it online. It does seem odd that I can't add a charged battery w/out telling the system or it will malfunction.

If the engine were running and someone added a charger then I could see where the BMS would be confused and potentially do the wrong thing because another power source was added.
 

RebelYankee

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So update. I over fixed it. Charged the battery off the car, waited an hour, and hooked it back up. Using gap, I reset the bcm. Being the idiot that I am, I also reset the secondary battery. So now the freaking stop start is working again.

I did take off my seatbelt so I could test it and the car still shudders a little, but when I add hvac, seat heaters, etc., it doesn't dip in rpm's like it used to. I guess that's a good sign.

Back to the drawing board.
 

RebelYankee

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Still chasing this issue. I did a smoke test and found some small leaks in the intake. The clamp on the throttle body was stripped. I replaced it (NAPA sells then as European Clamps) and that didn't fix the issue. Had the battery checked and is good. I checked the fuel rail pressures while driving, and the actual is always lower than the desired. Is that normal?
 

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