[PolePosition]

2021 Challenger Hellcat Redeye Widebody | Automatic | Stock | ~5000 miles

Dealer replaced defective throttle body, updated PCM, and reset adaptives. Now my car neither decelerates when I let off the gas nor engine brakes downhill. On cruise control, the car used to engine brake downhill to maintain the set speed, now it just accelerates without resistance. It’s driving me nuts.

Would disconnecting the battery overnight undo any customizations or setting changes the technician may have done—i.e., reset to Dodge factory defaults?

I’m not very mechanically knowledgeable, but I would appreciate any ideas you might have about what’s happening and how to fix it—without aftermarket modifications please.

Thank you to everyone.

 

[2ndAmend]

Don't know about Dodge, but my chevy truck took maybe 1/2 hour to reprogram itself after cleaning the throttle body.

How much have you driven it since it was replaced?

Also check if there is a reprogram procedure like suggested for my truck, something like the key to "on" (in this case "RUN") and press the throttle to the floor, then release, and do it a couple times. My guess was that it neaded to relearn where the full open and full closed positions were.

 

[Ross61]

I am trying to recall if my Durango ever downshifted when in cruise and I do not think so. I am pretty sure is just "coasted" and I had to be cognizant of speed creep.

On the GTO (manual), it would let off on the fuel and the tranny would help keep the speed if the hill was so steep.

Are you manual or automatic?

 

[PolePosition]

Don't know about Dodge, but my chevy truck took maybe 1/2 hour to reprogram itself after cleaning the throttle body.

How much have you driven it since it was replaced?

Also check if there is a reprogram procedure like suggested for my truck, something like the key to "on" (in this case "RUN") and press the throttle to the floor, then release, and do it a couple times. My guess was that it neaded to relearn where the full open and full closed positions were.

Thanks @2ndAmend. I’ve only driven about 40 miles since the throttle body replacement. Maybe someone can post, or point me in the direction of, the relearn procedure. Either way, thanks, I’ll look into it.

 

[Blickie]

2021 Challenger Hellcat Redeye Widebody | Automatic | Stock | ~5000 miles

Dealer replaced defective throttle body, updated PCM, and reset adaptives. Now my car neither decelerates when I let off the gas nor engine brakes downhill. On cruise control, the car used to engine brake downhill to maintain the set speed, now it just accelerates without resistance. It’s driving me nuts.

Would disconnecting the battery overnight undo any customizations or setting changes the technician may have done—i.e., reset to Dodge factory defaults?

I’m not very mechanically knowledgeable, but I would appreciate any ideas you might have about what’s happening and how to fix it—without aftermarket modifications please.

Thank you to everyone.

Disconnecting the battery overnight won't hurt anything and would check that box...

 

[PolePosition]

I am trying to recall if my Durango ever downshifted when in cruise and I do not think so. I am pretty sure is just "coasted" and I had to be cognizant of speed creep.

On the GTO (manual), it would let off on the fuel and the tranny would help keep the speed if the hill was so steep.

Are you manual or automatic?

Hi @Ross61. My wife says I'm definitely a manual, but the car is an automatic. I’ve driven it for ~5000, so I know how it used to behave. I live in a mountainous area. There are very few level and straight roads here. I hate riding the brakes as I'm now required to do.

 

[PolePosition]

Disconnecting the battery overnight won't hurt anything and would check that box...

@Blickie, thanks. Do you know if pulling the battery would undo any customizations the tech might have done, or would it just reload the last known (customized) settings?

 

[ledft]

Thanks @2ndAmend. I’ve only driven about 40 miles since the throttle body replacement. Maybe someone can post, or point me in the direction of, the relearn procedure. Either way, thanks, I’ll look into it.

You may have to drive a lot more than 40 miles. Seems it was weeks of experimentation with the performance pages to get mine to shift without a bang and smooth out. I would definitely miss the engine braking. Good luck

 

[ledft]

I think it’s a slow learning car because it’s got so many ways t go😁

 

[Blickie]

@Blickie, thanks. Do you know if pulling the battery would undo any customizations the tech might have done, or would it just reload the last known (customized) settings?

While exact answers are hard to find, it's generally thought to reset most everything, including the PCM.

 

[Anguish]

While exact answers are hard to find, it's generally thought to reset most everything, including the PCM.

It will also reset any progress towards the PCM learning the car and the driver's habits.

 

[Unholy707]

Honestly, sometimes resetting the adaptive does more harm then good. Because if you baby it after they’re reset? That’s how it’s going to learn throttle response. A lot of people also don’t realize that the TCM has a very specific relearn procedure. You could completely screw up your up and downshifts if you reset the adaptives and don’t go through the correct procedure, resulting in jerky/hard shifts. Don’t even get me started on a tuned car, or dare I say, a flex fuel tuned car. NEVER reset the engine adaptives if you have a flex fuel calibration.

 

[PolePosition]

Honestly, sometimes resetting the adaptive does more harm then good. Because if you baby it after they’re reset? That’s how it’s going to learn throttle response. A lot of people also don’t realize that the TCM has a very specific relearn procedure. You could completely screw up your up and downshifts if you reset the adaptives and don’t go through the correct procedure, resulting in jerky/hard shifts. Don’t even get me started on a tuned car, or dare I say, a flex fuel tuned car. NEVER reset the engine adaptives if you have a flex fuel calibration.

@Unholy707, thanks for the advice.

 

[PolePosition]

It will also reset any progress towards the PCM learning the car and the driver's habits.

Thanks @Anguish.

 

[baabootoo]

Did the dealer tell you anything? With the engine braking, how do you know that was normal before the work? Maybe it's "normal" now. Mine doesn't really engine brake in STREET mode anyway.

 

[Mattm400]

Mine has always done it, I have a very long driveway with slight slope, mine always downshifts & holds a gear when coasting down even at that low speed.

 

[ledft]

Did the dealer tell you anything? With the engine braking, how do you know that was normal before the work? Maybe it's "normal" now. Mine doesn't really engine brake in STREET mode anyway.

I just checked my 2015 Charger HC to verify it’s in street mode and it is. I get plenty of engine brake when driving and more so on cruise control.
I still have original brake pads and rotors on the rear, original rotors on the front, and I replaced the front pads with oem at 75K miles. The old cat has over 110K miles now. That’s significant engine braking on a big beast like that.

 

[PolePosition]

Update/Resolution: I pulled fuses 29 and 31 and kept them out for 4 hours while I did other things. I then replaced the fuses and ran some errands, driving for about 2 hours. The car is 100% back to normal now. I get engine breaking and the car holds the set cruise control speed even on steep declines.

Thank you to everyone for your help and advice. I know this issue was of interest to some of you, so I will continue to answer questions, if you have them.

 

[PolePosition]

Did the dealer tell you anything? With the engine braking, how do you know that was normal before the work? Maybe it's "normal" now. Mine doesn't really engine brake in STREET mode anyway.

I tried pulling fuses 29 and 31 before taking the car back to the dealership and the car returned to normal, so the dealership didn’t have an opportunity to say anything about the issue. The throttle body was replaced as a troubleshooting step to resolve problems with the new Enhanced Valet Mode update; however, the original throttle body was not failing, and the new throttle body made no difference whatsoever. Since replacing my throttle body, Dodge has abandoned the Enhanced Security Valet mode update altogether, it is no longer available for installation. There is still a Star case open to fix the problems with the Enhanced Security Valet Mode, but as of now there are only 2 of the original 3 promised security updates available for our cars—the RF-Hub update and the new Alarm Module. So, to answer the question… I know my car’s engine braking behavior was normal because of (1) 5000 miles of driving experience, (2) the behavior changed suddenly after it was worked on by the dealer, and (3) the car is back to normal now after resetting the ECU and TCM. Incidentally, my car now engine brakes in all modes—ECO, Street, Sport, and Track.

 

[Hoss056]

Hard to say why. Updates can cause unintended issues and battery disconnects are usually one of the first things the Star Center will recommend for strange electronical concerns. This will not erase any adaptives in the PCM or TCM though. They have to be manually reset with a scan tool. Good to hear its resolved though.