Bucking while slowing down. Anybody else?

[TBD]

It’s gonna be a weird issue to try to describe so bear with me.
A few months ago my 24 Mav Lariat started randomly doing this. It happens most often while slowing down from highway speeds on a downhill like while exiting the freeway, but I’ve had it happen while slowing down on residential streets too. While I’m slowing down and get to anywhere between maybe 35 to 1mph the truck will buck REALLY hard feeling like it’s a manual trans and the clutch suddenly gets dropped. Sometimes it’s somewhat soft but noticeable and other times it’s so violent it feels like I’m getting rear ended.
I’ve tried troubleshooting on my own a little bit trying to notice any patterns for when it happens with little luck. I have the OBD fusion app installed with a Bluetooth adapter and I noticed one consistency but I have no idea what it means. I have a tab setup for hybrid battery readings (Battery %, battery power kW, etc). Whenever it happens, the battery power goes instantly to 0. No regen, no electric assist, it just sits at 0kW for about 20 seconds then slowly starts to work normally again.
Anybody else have this issue or maybe know what it could be? I’ve taken it into the dealer trying to replicate it with no success. I’d have to drive around with the advisor for an hour plus and they don’t have that much time just to verify my issue. Any input is appreciated!

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[Ford Motor Company]

Hello, I would be happy to take a look into things regarding your bucking concerns. Could you please send us a message with you VIN and mileage?

 

[KevCuRaoi]

It’s gonna be a weird issue to try to describe so bear with me.
A few months ago my 24 Mav Lariat started randomly doing this. It happens most often while slowing down from highway speeds on a downhill like while exiting the freeway, but I’ve had it happen while slowing down on residential streets too. While I’m slowing down and get to anywhere between maybe 35 to 1mph the truck will buck REALLY hard feeling like it’s a manual trans and the clutch suddenly gets dropped. Sometimes it’s somewhat soft but noticeable and other times it’s so violent it feels like I’m getting rear ended.
I’ve tried troubleshooting on my own a little bit trying to notice any patterns for when it happens with little luck. I have the OBD fusion app installed with a Bluetooth adapter and I noticed one consistency but I have no idea what it means. I have a tab setup for hybrid battery readings (Battery %, battery power kW, etc). Whenever it happens, the battery power goes instantly to 0. No regen, no electric assist, it just sits at 0kW for about 20 seconds then slowly starts to work normally again.
Anybody else have this issue or maybe know what it could be? I’ve taken it into the dealer trying to replicate it with no success. I’d have to drive around with the advisor for an hour plus and they don’t have that much time just to verify my issue. Any input is appreciated!

This recall doesn't cover 24 Mavericks....but it does sounds similar to the issue covered by 24S24:

On your vehicle, the Body Control Module (BCM) and Powertrain Control
Module (PCM) calibrations may be unable to detect a sudden change in the
12-volt battery state of charge during a drive cycle.

If the BCM and PCM calibrations are unable to detect a sudden battery
degradation during a drive, the vehicle may be unable to restart or may
experience a stall while coming to a stop at low speed. The vehicle may
also lose electrical accessories such as hazard lights or cause a loss of
drive power increasing the risk of a crash.

Does your Maverick have any recalls? (There may be a similar one for 24s that I am unaware of). Did dealership try any PCM or BCM updates?

 

[rallyshark]

Following...

 

[mp24]

Hello, I would be happy to take a look into things regarding your bucking concerns. Could you please send us a message with you VIN and mileage?

stop posting, you're not helping anybody

OP: you're CV axles need to be replaced. it's a very common issue. they'll be replaced with the same part, so expect the issue to occur again in the future.

 

[Jebadent]

It’s gonna be a weird issue to try to describe so bear with me.
A few months ago my 24 Mav Lariat started randomly doing this. It happens most often while slowing down from highway speeds on a downhill like while exiting the freeway, but I’ve had it happen while slowing down on residential streets too. While I’m slowing down and get to anywhere between maybe 35 to 1mph the truck will buck REALLY hard feeling like it’s a manual trans and the clutch suddenly gets dropped. Sometimes it’s somewhat soft but noticeable and other times it’s so violent it feels like I’m getting rear ended.
I’ve tried troubleshooting on my own a little bit trying to notice any patterns for when it happens with little luck. I have the OBD fusion app installed with a Bluetooth adapter and I noticed one consistency but I have no idea what it means. I have a tab setup for hybrid battery readings (Battery %, battery power kW, etc). Whenever it happens, the battery power goes instantly to 0. No regen, no electric assist, it just sits at 0kW for about 20 seconds then slowly starts to work normally again.
Anybody else have this issue or maybe know what it could be? I’ve taken it into the dealer trying to replicate it with no success. I’d have to drive around with the advisor for an hour plus and they don’t have that much time just to verify my issue. Any input is appreciated!

I have almost same issue. This is what I've noticed. When slowing down once I get to about 5-10 miles and hour usually. Same thing truck starts clunking to a stop. Seems to be when the gas motor is sutting off. Sometimes when slowing down at 30-40 truck feels like the regenerative braking releases for a split second and then grabs again. This only started after the first BCM update and is getting worse. It has had the second BCM update as well. I was hoping it would fix it but hasn't. I'm in the same boat. Doesn't do it all the time. But does usually do it almost every time it sits over night and I first start driving it in the morning. 23 XLT Maverick vin# 3FTTW8E39PRA65954 My bosses 23 does this periodically as well

 

[skyhawk]

stop posting, you're not helping anybody

OP: you're CV axles need to be replaced. it's a very common issue. they'll be replaced with the same part, so expect the issue to occur again in the future.

This does not sound like a CV axle problem to me. Sounds like a transmission / regen related issue

 

[rallyshark]

I think I remember someone else mentioning this problem, and the solution was replacing the high voltage battery. I'm hoping others will chime in on this. I'm having the exact same issue, but it isn't super often. When coming to a stop from highway speeds, it's like the regen releases and the truck surges like I let off the brakes, and sometimes I'll get the clunk(s). It is a rather dramatic one at that. Just like the OP said, it's like dropping the clutch on a stick.

Again, this doesn't happen to me a lot. I have a '23 XLT with about 41k on it. I did the updates in March or May(can't remember), but haven't done the latest. I didn't have this issue prior to the last update either... I was hoping when I get the latest updates it would fix the issue, but Jebadent's previous reply kind of poops on that hope.

 

[TBD]

I think I remember someone else mentioning this problem, and the solution was replacing the high voltage battery. I'm hoping others will chime in on this. I'm having the exact same issue, but it isn't super often. When coming to a stop from highway speeds, it's like the regen releases and the truck surges like I let off the brakes, and sometimes I'll get the clunk(s). It is a rather dramatic one at that. Just like the OP said, it's like dropping the clutch on a stick.

Again, this doesn't happen to me a lot. I have a '23 XLT with about 41k on it. I did the updates in March or May(can't remember), but haven't done the latest. I didn't have this issue prior to the last update either... I was hoping when I get the latest updates it would fix the issue, but Jebadent's previous reply kind of poops on that hope.

That’s EXACTLY what’s happening. It’s like the brakes let up for a few seconds then bang. Do you remember anything about the other post that you saw that might help me find it? Maybe there’s something in there about what tests they did to narrow it down to tue battery being the problem and I can request my dealer to do the same tests. This definitely shouldn’t be happening to our new trucks

 

[HeyBales]

The HVBattery cannot be overcharged - that would be a problem.

So despite being on the highway perhaps your HVB SOC is up at 70% already, considered the max normally.

But now you have this strong segment of regen going on and that remaining 30% fills fast, and the computer is going to allow the engine to spin up to take some of the load since it can't be sent to the battery. Engine isn't on, merely taking the energy from the wheels.

So you have this swap from motor resistance to engine resistance and perhaps more physical braking in there, maybe all about the same time.

I'm sure things are feeling strange, and that would take some programming to improve when that happens.

People report on long downhills coasting they can feel the engine being allowed to spin up for the same reason - but usually no braking going on so really not going to feel the difference.
But on the gauges it can be seen, and it's heard.

Since you have some gauges - look at the HVB SOC and see if it's over 70% when it happens - I saw 87% one time.
If you have engine RPM, see if that is showing a figure even though your dash gauge shows you in the blue for hybrid or regen probably.

 

[TBD]

The HVBattery cannot be overcharged - that would be a problem.

So despite being on the highway perhaps your HVB SOC is up at 70% already, considered the max normally.

But now you have this strong segment of regen going on and that remaining 30% fills fast, and the computer is going to allow the engine to spin up to take some of the load since it can't be sent to the battery. Engine isn't on, merely taking the energy from the wheels.

So you have this swap from motor resistance to engine resistance and perhaps more physical braking in there, maybe all about the same time.

I'm sure things are feeling strange, and that would take some programming to improve when that happens.

People report on long downhills coasting they can feel the engine being allowed to spin up for the same reason - but usually no braking going on so really not going to feel the difference.
But on the gauges it can be seen, and it's heard.

Since you have some gauges - look at the HVB SOC and see if it's over 70% when it happens - I saw 87% one time.
If you have engine RPM, see if that is showing a figure even though your dash gauge shows you in the blue for hybrid or regen probably.

I’m aware of this and I definitely hear you. However I’ve been keeping track of HV Battery SOC the last few times it happened and it’s always 45-60% which from keeping an eye on it for a while 60% is about 3/4 of the range that the battery likes to stay in. From what I’ve seen it likes to stay between 30% and 70%. Since the issue happens even at 45% SOC I don’t think it’s the overcharge protection you’re suggesting might be what we’re experiencing.

I noticed pretty shortly after buying the truck the engine braking while on a long downhill. Made complete sense to me and also the truck did a great job transitioning from regen to engine braking. However this issue is completely different from that. The battery won’t be even close to what it considers full (70%) and it mostly relies on the disk brakes as opposed to engine brakes after the “bang”. I really do appreciate your input but I don’t think this is what we’re dealing with here. Cheers!

 

[TBD]

The HVBattery cannot be overcharged - that would be a problem.

So despite being on the highway perhaps your HVB SOC is up at 70% already, considered the max normally.

But now you have this strong segment of regen going on and that remaining 30% fills fast, and the computer is going to allow the engine to spin up to take some of the load since it can't be sent to the battery. Engine isn't on, merely taking the energy from the wheels.

So you have this swap from motor resistance to engine resistance and perhaps more physical braking in there, maybe all about the same time.

I'm sure things are feeling strange, and that would take some programming to improve when that happens.

People report on long downhills coasting they can feel the engine being allowed to spin up for the same reason - but usually no braking going on so really not going to feel the difference.
But on the gauges it can be seen, and it's heard.

Since you have some gauges - look at the HVB SOC and see if it's over 70% when it happens - I saw 87% one time.
If you have engine RPM, see if that is showing a figure even though your dash gauge shows you in the blue for hybrid or regen probably.

Here’s a screenshot of my record of the last few times I’ve had the issue. The temperature is outside ambient temp not the HV Battery temp.

 

[TBD]

If there are any other parameters I could/should be writing down to help narrow down the problem I’m open to suggestions

 

[rallyshark]

That’s EXACTLY what’s happening. It’s like the brakes let up for a few seconds then bang. Do you remember anything about the other post that you saw that might help me find it? Maybe there’s something in there about what tests they did to narrow it down to tue battery being the problem and I can request my dealer to do the same tests. This definitely shouldn’t be happening to our new trucks

I suck man, I don't remember the other details of the post I wish I could find it to link here, but no luck. I remember being surprised that the dealer said replacing the HV battery was the solution, and the person that made the post said the problem seemed to be resolved. It had only been a day or two since the repair had been made. I kind of disregarded it, given the lack of time/testing after the battery was replaced. I had hoped they would post again after some proper driving had been done.

Hopefully, we'll get another post or person chiming in to confirm the solution soon. I drive a lot, and don't have time to leave my truck at the dealer for "hopeful fixes". I need to see some definite solutions to point the dealer to in order to minimize the time my truck is there. Of course, I'll have to deal with it at some point. I'd just prefer to have a high degree of confidence that the solution is known, before I go there.

 

[Bandit1]

I've had this same issue of the regen letting go and charging goes to zero. I've got the scanguage 3 and have been watching to see what is triggering this. What I've come to the conclusion is every time the battery voltage exceeds 250v it triggers this event, regardless of the HVB SOC%

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