I picked up a 2016 LR4 with 77,000 Miles with a rebuilt title from a trade in. Showed a "Charging System Fault" and I didn't think much of it as it's typically just an alternator, battery or something straight forward. Drove it home and found all the service records (over $8,800 in three years, including ball joints, coolant leaks, etc) from the previous owner who had chased in problem for over a year and gave up.

Battery shows 12.7V
When running 13.6V

SERVICE RELATED HISTORY (per shop receipts):
Previous owner bought it in 2022 as a rebuilt with 42k.
AUG of 2023: 64K MILES, He replaced the alternator by an independent shop.

AUG 2024: Independent shop service to diagnose the "Charging System Fault", proceeded with the following:

1. Direct Comment from Technician: "Vehicle is requesting 14.2v vehicle is charging at 13.6. Tested signal wire from BMS module (battery monitoring system module) back to Gateway Module. Confirmed integrity and can hold a load. Updated software on gateway module. No change. Inspected and found vehicle data shows incorrect battery installed. Inspected and found lead acid battery installed. Called dealer and confirmed agm battery should be in place. Recommend before any further testing that new agm battery be installed then continue diag if no change."
2. Shop replaced with new NAPA AGM battery. Direct Comment from Technician: "Installed new battery, and the system is still showing a charging fault indicator. I tested the LIN (local interconnect network) communication wire from the alternator and the PCM. I checked for continuity between the the pom and the alternator on the LIN circuit. I have good resistance there. I load tested the circuit. All checks out there as well. Then tested circuit for a short to ground. Checks okay there."
3. Installed New Alternator from JLR ($1,200), however, it appears to be a re-manufactered. Direct comment from Technitian: "Per Land Rover/ jaguar specs, installed new alternator, installed new battery, tested all circuits for opens, high resistance, short to ground, and load tested circuit. Based off testing results and Land Rover specs, Land Rover says to replace PCM (powertrain control module )"
4. Shop could not resolve, suggested replacing the PCM.

SEPT 2024 Owner took the vehicle to the local JLR Dealer:

1. Technician comment: "Verified the customers complaint, but also noticed that the eco light comes on right before or at the same time as the charging system fault message. Checked fault codes and the GWM has had faults set for the secondary battery and the generator control module (B13C5-92, POA1A-87) Checked the charging system at the main 12v battery and measured 13.6v, checked the aux 12v battery and measured 9.3v. Found that the power distribution box has failed and has caused the aux 12v battery to fail and is causing the charging system fault message to come on due to not charging the aux 12v battery properly. Est power distribution box and aux 12v battery"
2. Replaced the secondary Start/Stop battery. (Not confirmed if through dealer or not)
3. Replaced the Power Distribution Box. (Not confirmed if through dealer or not)

ALL THIS DID NOT RESOLVE THE "CHARGING SYSTEM FAULT".


CURRENT TESTING AND DIAGNOSTICS:

1. Battery currently tests at 12.7 V. (manufacture Date of 05/2024) Passed test from Nampa. I did have to put it on a charger to get it back to 100% and re-installed. Only added a few more seconds to the warning message upon start-up.
2. When running, the charging system is at 13.6 V and does not increase.
3. I have tested under maximum load by running all electronics I could think of (AC, heated seats, heated windshields, stereo, headlights, etc) and the charging system does not go above 13.6V.
4. Grounds show no significant voltage drops. No visible corrosion, and no corrosion at the right-wheel arch.
5. Tested the positive wire for the BMS back to the BMS sensor. minimal resistance
6. Tested positive to the alternator.
7. Checked the "Power distribution box" near the secondary start/stop battery. When running, 13.6 V to all three points. When turned off, 13.2 V from the secondary battery, 12.7V to the other points (from main battery, to fuse box).
8. Removed alternator and had it tested at Autozone. Passed test with around 14.33 under load.

There has also been an oil leak from the Vacuum Pump near the alternator for some time. I had to replace the alternator on my 2019 Discovery (around 60k) because of the oil leak which also showed a "Charging System Fault" message. I assume the oil leak had ruined the FIRST Alternator the previous owner installed in AUG 2023.

Question: I did not test the LIN Communication wire to the back of the battery, Any other way to confirm without an oscilloscope?

Any suggestions? I feel like the JLR Dealer didn't do a good job and diagnosing, but did find "a problem" and assumed it was the cause.

Thanks in advance!

 

Ha! I know the feeling. I have a 2016 LR4 and just picked up a 2020 L405. Its the devil you know...

It sounds like you probably will have yourself a great deal once you figure this mystery out. I assume its something way cheaper than a dealer throwing 8k in parts to figure out...I just dont know what.

I have fixed most everything to be fixed on my LR4 but electricity is still a dark art to me. I never had any alt issues and I swapped multiple main batteries and eco batteries over the years and it was always just plug and play. On my L405, however, people say it's imperative to get the BMS reset and battery registered after changing the battery.

I think a valve cover leak is usually the bigger culprit leaking down on the alternator vs the vacuum pump blowing back on it. Ive had both and had some oil around the alternator, but that was from the valve cover.

The L405 is notorious for corroded grounds and im wondering if thats your issue, or they didnt properly connect one of the ground straps when replacing the engine. On the L405 there are a bunch of wonky errors you will get if either the ground stud or electrical junction box behind the front wheel arch lines get corrosions on them.

 

The BMS was reset when the Independent shop put a new battery in it.

The oil leak is definitely the Booster Pump. Here is a pic of before I spent several hours cleaning all the grease build up. Helps when chasing oil and coolant leaks. I know as it was the exact same problem on my 2019.



Doubt it's a grounding issue, as it would be throwing other things off.

 

Ok I am new to these, but try something simple disconnect the aux battery, see if there is a change. I get 14.3 or more volts when my engine is running at both batteries, but before I disconnected then replaced my aux battery my charging voltage was much lower, down to as low a 13.

But my bet is your BMS is shot or was never reset it really needs to reset with a new battery The reset should be done on a fully charged battery.

A gap tool or this process should do it- the gap tool is best.


Disconnect both your negative ( - ) and positive ( + ) battery clamps from the battery terminals, starting with the Negative first, and leave them that way for about 20 minutes.
Next, get any short length of wire and join the negative ( - ) and positive ( + ) battery CLAMPS, NOT the battery terminals.
You only need to touch them together for a few seconds.
Then reconnect the battery clamps to the battery terminals, putting the Positive clamp on first.
Then see if you are still getting the warning messages.
This procedure normally resets the vehicle's BMS.

 

Thanks Richard!

I also spoke to a local independent rover shop, and he speculates it could be the alternator is not communicating property with the vehicle, even though it's fine on a bench test. So I was going to remove my functional alternator from the D5 (2019, same alternator) and see how it goes!

 

@macro1 Yea they all forget about the BMS, in the end it controls the charge rate

 

UPDATE:

Removed the alternator from the '19 D5, installed the one from the D4... no fault codes on the D5.

However, I noticed the alternator LIN wire was replaced with an aftermarket pigtail at some point. (see pics). Looks like they modified the connector to make it fit.

I ordered a replacement.

 

UPDATE:

Still no fix. GAP TOOL had the following codes:

Vehicle scanned on 06-02-2026 12:01
Using IIDTool BT V4.0 B0098

BCM-Body Control

• U0241-00 (2E) Lost communication with the headlamp control module A
  ( on 06-02-2026 11:53:52 at 78845 mi )

GWM-Gateway module

• P0A1A-87 (2F) Generator control module - Bus signal/message failure - missing a message
  ( on 27-01-2026 20:44:55 at 78845 mi )

HVAC-Ventilation

• B13C2-86 (2F) Windshield misting sensor - Bus signal/message failure - signal is invalid
  ( on 27-01-2026 20:44:55 at 78845 mi )
• B13C2-96 (2F) Windshield misting sensor - Component failure - internal failure
  ( on 27-01-2026 20:44:55 at 78845 mi )

RCM-Airbag

• B1212-13 (AB) Driver safety belt buckle pretensioner deployment control - General electrical failure - circuit open
  ( on 27-01-2026 20:45:08 at 78845 mi )
  
  
• 
  

I also located a pinched wire from the harness to the alternator, did a temporary twist and after 30-sec from startup the charging system fault returned.

I then ran a temporary wire directly to the alternator to bypass the previous repair. Again, after 30-sec from start the charging system fault returned.


Any ideas based on the fault code P0A1A-87 (2F) ?

 

Check this post https://www.landroverworld.org/threa...m-fault.30261/

 

I saw that a while ago. The service records show that a local shop (although not LR specialized) attempted a ECU Flash in 2024.

Is there a better way to flash the ECU (such as through the GAP tool)?