Trek Rail 9.9 AXS - Error Code - Question

AKAKTM

Member
Apr 23, 2020
35
53
Santa Clarita, CA
I recently sold my 2019 Turbo Levo Expert, which was a great bike, and bought a Rail 9.9 AXS. The 9.9 AXS is a cool bike, but it's been more trouble so far than the Levo. The Levo was trouble free over more than 1k miles.

The Trek had several minor setup issues that were easily resolved.Within the first 100 miles the chainring bolt came loose twice before a local Trek dealer used Loctite and torqued it back down. After solving the setup matters and dialing in the suspension and such, the bike is/was getting to be really fun...until today.

With 297 miles showing on the display, the bike flashed some sort of error code - 504. I looked in the manual and learned it has something to do with the speed sensor. I looked at the sensor on the rear triangle and on the rotor and both appear perfect with no issues. There is no suggestion as to what's specifically wrong or how to resolve it. The display simply says call the dealer (again - they have been great). I'll call in the morning, but I must say the Rail has had more troubles and visits to the shop in the first few weeks than the Levo had in more than a year (never went to the shop). At this point I have a bike that seems to be reduced in output and limited to a very low speed.

Again, the bike is really nice, but between this 504 error, other minor issues and a motor that clacks going downhill and a couple of creaks under heavy peddling, I am growing frustrated. The dealer told me the clattering in the motor is normal and part of an internal freewheel mech. I'm chasing down the creaks, but this 504 thing is a drag!

I realize this is a brand new model and Trek really tried to deliver a world class bike, which I appreciate. I hope this gets resolved soon or I'll be looking to get back to a Specialized or see what's coming next.

How do I get rid of this 504 code?

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Last edited:

Paul Mac

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Unfortunately the 504 error has been an issue on some of the gen 4 motors, not a Trek issue, but all Bosch equipped bikes.
Fortunately there is a firmware update that resolves this.
Stick with it, it's a great bike?
 

AKAKTM

Member
Apr 23, 2020
35
53
Santa Clarita, CA
Unfortunately the 504 error has been an issue on some of the gen 4 motors, not a Trek issue, but all Bosch equipped bikes.
Fortunately there is a firmware update that resolves this.
Stick with it, it's a great bike?
Thank you. The firmware was upgraded less than a month ago when it was in to have the chainring bolt fixed a second time. Has new firmware been released in May?
 

Paul Mac

E*POWAH Elite World Champion
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Thank you. The firmware was upgraded less than a month ago when it was in to have the chainring bolt fixed a second time. Has new firmware been released in May?
Not that I know of.
But now you have the error, it might be that when they reset it, it resets the values to stop further incident.
Three of us all have Rails and none have got the 504 error yet, I have over 1000 miles in mine now.
 

Doomanic

🛠️Wrecker🛠️
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Jan 21, 2018
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504 is tuning detected, are you using any form of tuning?
 

Doomanic

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That's not good; the new firmware was supposed to stop the false positives.

To reset it you need to ride for 90 minutes. I'd be discussing it with your dealer though.
 

AKAKTM

Member
Apr 23, 2020
35
53
Santa Clarita, CA
That's not good; the new firmware was supposed to stop the false positives.

To reset it you need to ride for 90 minutes. I'd be discussing it with your dealer though.
Is my software the latest? I do not know. Ride for 90 minutes with little or no support! That's not good. I will be visiting the dealer.
 

p3eps

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Dec 14, 2019
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Scotland
Dealer reset it today for me. Warned me to try not to let it happen again! Not sure how to avoid it. BOSCH? Let's get this fixed.

Glad you didn’t need to ride for 90mins with no support! You’d have had to have found a very flat route for that, as my Rail 9.9 wasn’t much fun when switched off!!
 

pgtips

Well-known member
Patreon
Jun 3, 2018
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279
Somerset
 

dixie600mhz

Active member
Oct 13, 2020
174
159
Austin, Texas
I ordered a 2021 9.8XT and if I get a 504 on the stock bike I'll be asking for my money back same day. When I googled it and read the bullsh*t article below my blood boiled. I don't live in a nanny state where there's a 20mph limit. The more I read about this bike the less impressed I'm getting.

Can I change the chain ring without getting a 504? What's next, Camera's or trackers installed on our bikes because of some euro law garbage.
 

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