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Discussion Starter #1
FAULT = “Okay to drive. Reduced brake feel.” Fault light remains after multiple restarts and miles traveled. I actually don’t notice any difference in the brake feel from before and after the fault. MyPace app shows 12v batt at 14.6v, but not sure which of the 2 aux batts this applies to. Off to the dealer tomorrow.
 

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If you have battery measuring skills and a DMM, you could measure both the larger "Starting Battery" and the smaller "Aux Battery" voltages.

The batteries are concealed below the central removable cover behind the "froot" storage bin. Loosen the 2 + head screws and pull the fasteners from the rear vertical edge.The cover will come out if you wiggle it loose.

I have measured my batteries once, they had identical values. These batteries have differing technologies and I believe that 14.6 Volts is excessive for the AGM Aux Battery. If this voltage is constantly applied to the Aux battery, it will over time boil dry and will then fail to back up the critical services.

Cheers, Steve
 

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The brake feel sounds like a fault with the brake pedal position sensor or the feedback loop. If yes, it should still stop ok, you will just not have as much feedback from the system.
 

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Discussion Starter #5
Ugh, Brake Feel Warning just progressed to I-Pace not starting, with 2 new faults: TCU Battery and Gearbox Fault detected. Seems like this is a common progression from the initial Brake Feel Warning. Also, Parking Brake indicator in the dash and the parking button in the center console gear selection area both blink when attempting to power up the I-Pace. Now, how do I get the I-Pace out of my garage? Waiting for call back from dealer.
 

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Reads like the auxiliary battery has gone bad. Got a battery charger (not a trickle charger)? Remove the center panel in the frunk (the one you remove to check fluid levels) and attach it to the small battery on the driver side (you'll see the red cap over the positive post buried in there). It might get enough power to it to allow the car to awaken and get the parking brake released.

There's also the manual transmission park release. That is a little lever tucked in between the coolant hoses just behind the storage bin.
See: There are Cables to put car in Neutral, open hood / bonnett
 

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Discussion Starter #7
If you have battery measuring skills and a DMM, you could measure both the larger "Starting Battery" and the smaller "Aux Battery" voltages.

I have measured my batteries once, they had identical values. These batteries have differing technologies and I believe that 14.6 Volts is excessive for the AGM Aux Battery. If this voltage is constantly applied to the Aux battery, it will over time boil dry and will then fail to back up the critical services.

Cheers, Steve
Thanks Steve.
I measured both the starting and aux batteries with a DMM. Starting Batt = 14.47 v. Aux Batt = 5.46 v. So, I’m hoping the reduced brake feel, TCU Batt, GearBox, and pulsing brake pedal faults are related to the low Aux Batt voltage, rather than the frayed gearbox wiring harness issue.

Had my I-Pace tolled to the dealer. It was a hassle figuring out how to release the electronic parking brake. It took multiple tries. I really had to mash down on the brake pedal, which sounded like a goat (as many on this forum have experienced). Thanks to info in the forum, I also pulled the emergency transmission park release cable in the frunk.

Let’s see what my dealer diagnose ...
 

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Hi squishball, Your Aux battery voltage at 5.6 V indicates that it is beyond recovery, and will have to be replaced.

It is fortunate that you did not drive after the warnings, when this happens there have been reports of major noises from the transmission locking pall grinding into destruction, requiring major repair surgery and replacement parts.

It would be interesting if your dealer could very accurately measure the weights of your dead battery and the replacement battery, using a digital scale that measures to 3 decimal places i.e. 0.001Kg. This could indicate if the battery has boiled dry due to overcharging or if they are of identical weights, died from undercharging.

These AGM batteries have only a small volume of liquid electrolyte, as the plates are kept moist but not submerged or flooded in electrolyte.

I hope you are back on the road ASAP.

Cheers, Steve
 

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It would be interesting if your dealer could very accurately measure the weights of your dead battery and the replacement battery, using a digital scale that measures to 3 decimal places i.e. 0.001Kg. This could indicate if the battery has boiled dry due to overcharging or if they are of identical weights, died from undercharging.
Love this idea! 0.001kg = 1g, but the point is that the battery is quite heavy so the scale has to have high precision.
 

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This.

My kitchen scales are rated 5kg max, read to 1gram and my workshop 300Kg scales read to only 2 decimal places = 10gm.

These batteries hold very little free electrolyte, so not much of a difference to measure. btw I have never done this but it would be interesting to see.

The other sign of AGM overcharging is bulging ends of the battery case.

Cheers, Steve
 

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Discussion Starter #11
It is fortunate that you did not drive after the warnings, when this happens there have been reports of major noises from the transmission locking pall grinding into destruction, requiring major repair surgery and replacement parts.
Steve, I did drive my I-Pace, but only when it displayed the single warning fault. “okay to drive, ... reduced brake feel.” The I-Pace drove fine, with no unusual sounds coming from the drive system. I guess I was lucky, because when I started up the I-Pace this morning to drive it to my dealer to take care of the ”reduced brake feel” warning, it wouldn’t power up the drive system. The dash simultaneously displayed the TCU Batt, Gearbox, and ASPC faults. This may have been an intentional safety feature of the I-Pace, but regardless, it prevented me from driving it and incurring potential drive train damage.
 

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Discussion Starter #12
Update on my I-Pace. Vehicle was flat-bedded to local Jag dealer last Wednesday. As of today, they’ve replaced both the starter and aux 12v batteries, which as many in this forum have indicated as the primary cause of the warning code “reduced brake feel” and probably let to the cascading of the other codes listed in an earlier posts. I believe they’ve also updated some software, but the service manager wasn’t specific. Unfortunately, the I-Pace is still throwing DTCs, and the tech’s don’t know what they mean. They’re going to let the I-Pace sit for several hours to overnight and then reboot to see if the DTCs self-correct. If not, they’re going to open a case with JLR. Hopefully, the codes don’t reappear.
 

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Discussion Starter #13
Update on my update. Got my I-Pace back today. :) As the forum has correctly diagnosed, the fault codes starting with Reduced Brake Feel and then eventually cascading to not being able to power up the drive system with the addition of TCU Batt, GearBox, and ASPC faults was due to a bad 12 v auxiliary batt (officially know as a Brake Booster Batt) and a bad 12 v starter batt. Dealer also updated software, but no specifics were provided in the service receipt.
 

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I seem to notice a correlation of those that repair their I-Pace soon after "Drive with caution brake pedal feel reduced" fault appears often only the auxiliary battery is replaced. Those who start with "Drive ....." fault and eventually get numerous faults and car will not get out of park usually get both 12 volt batteries replaced. This of course is just an unscientific observation.
 

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Sounds like the replacement of the auxiliary battery should be a first resort, rather than a trip to the dealer. Are these batteries standard specs that could be purchased independant of JLR?
 

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"AYEPACE" showed the auxiliary battery to be an AGM made by Exide and was 12V, 14Ah, and 200A. I imagine this battery specifications could be found elsewhere. Of course JLR will pay for it during the warranty period. After that it might be worth looking into an alternative.
 

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Discussion Starter #17
I seem to notice a correlation of those that repair their I-Pace soon after appears often only the auxiliary battery is replaced. Those who start with "Drive ....." fault and eventually get numerous faults and car will not get out of park usually get both 12 volt batteries replaced. This of course is just an unscientific observation.
I totally agree. I drove my I-Pace for a day after the "Drive with caution brake pedal feel reduced" fault appeared. The following day, I had an appt. with the dealer, which of course was when the I-Pace decided to misbehave and seize up with the aforementioned faults. Based on my experience, I recommend all I-Pace users immediately measure the voltage to the auxiliary batt when the "Drive with caution brake pedal feel reduced" fault appears. If it’s below 12-13 v, head to the dealer immediately, before your I-Pace seizes up and have to resort to a flatbed tow. Alternatively, charge the auxiliary batt and then head to the dealer. Qtown is correct that you can DIY replace the batt, but why not use our cost free warranty.
 

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I seem to notice a correlation of those that repair their I-Pace soon after "Drive with caution brake pedal feel reduced" fault appears often only the auxiliary battery is replaced. Those who start with "Drive ....." fault and eventually get numerous faults and car will not get out of park usually get both 12 volt batteries replaced. This of course is just an unscientific observation.
In my case, where I was unable to get the car out of park and got all the standard fault codes, it turned out to be a bad ground connection rather than bad 12v batteries.
 

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.....Alternatively, charge the auxiliary batt and then head to the dealer. Qtown is correct that you can DIY replace the batt, but why not use our cost free warranty.
The question is whether there is a problem with this brand/model/batch of batteries, or is the car not charging them adequately?
Alternatively just having a replacement sitting on a shelf in the garage would seem prudent.
 

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The auxiliary battery is an EXIDE EK151 battery. Autospares.eu has sold and shipped to US through ebay.

Others on Jaguar and Rover sites have installed Deka East Penn Aux14 batteries, but this requires modification/adapting the cables or posts.
 
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