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Discussion Starter · #1 ·
a friend of mine has lifted his rene and put on bigger tires. he took it to the dealer who added a sales code to the BCM for a larger tire size. they told him up front the renegade has no ability to modify tire size and that this code was likely going to do nothing. and id did just that: nothing.

so i got out my trusty phone and alfaobd and went to work. there are some posts on the ram forum on how to change tire size there. and there is a post from someone on this forum saying it is possible.

well, i just wanted to say, IT IS POSSIBLE... it works great. there are some caveats you need to keep in mind, and had do do several other procedures with the ABS module to ise control to work again. here are my experiences:

1) alfaobd in the BCM under car config changes has the ability to set tire circumference in millimeters the stock tire size on the rene is 2129mm. this is regardless of the package you have. i have the altitude package with 18" wheels that are bigger then 2129 around (2212 to be exact), i consider my speedometer to be very accurate. so i believe that computer is doing some pinion adjustment based on the trim level specified in the BCM. so be sure to take this into consideration.

my friend has monster tires. his circumference is 2532. huge.

2) the first issue we had was that my phone copy of alfaobd and my obdlink mx+ refused to do a proxy align on his vehicle. after going going back and forth with the dev i finally got a windows version and a wired (obdlink sx) connector. this worked very well. i believe there is an issue in is ABS computer with the wrangler tire sales code that the dealer added. the dealer was unable to remove the added code as well... so he has further issues down the road. but in the mean time, we got proxy aligns to work

3) so the first thing i did once i was sure my computer worked with his car was to try and set his tire size to 2532. this did not work when i did a proxy align. it did not allow the configuration to be written to the drive train control module. the alfaobd dev said this is because it was too big of a number being written in.

i started the other way. i increased 2129 to 2219, did an align and it took it fine.
next i did 2329. worked like a charm.
next i did 2399 and it worked.
next 2429. and it worked.
finally i put in 2499.... and it took it.
when i tried 2500 it failed to write. so the maximum tire circumference you can set is 2499.

4) with our success i did nothing else but sent him for a drive. it worked for about 30 minutes. his cruise control would not stay engaged tho. he got no error message it would just turn it self off. on top of that, after he parked for 10 minutes with it off, he got back in and his speedometer was off again. back to what it showed with the original settings.

5) he brough his rene back. i checked the BCM and other modules and the tire size was what i set it at: 2499, but his instruments were all off. i backed off the number, back to 2450. then i followed as much of the tire setting size instructions i could in the ram forum:

abs -> Pressure Sensor calibration
abs -> longitudinal and latitudinal sensor calibration
abs -> wheel speed sensor recognition.

he went for a ride. speedometer was still off... back to the default readout. but his cruise control worked again! it is the little things i guess.

we decided to leave the setting in there, figuring it may need a 24 hour sleep cycle to take effect? the computers in these vehicles are weird beyond belief.

6) this is were we may have discovered a sleep cycle skipping hack. he had an upgraded uconnect radio he wanted installed. i did mine and it was easy, so i figured we could bang it out after the tire thing. unfortunately the person who sold him the radio got it out of a chrystler product, not a jeep (evident by the chrystler splash screen and not jeep).

we tried a couple of proxy aligns, but it kept failing. i could talk to the radio with alfaobd but i could not get the vehicle to recognize it. at a certain point in our messing around, there was a panic in the canbus... everything stopped talking to everything else. there were errors galore in all the modules.

we reversed course... unplugged the new wrong radio and put his old one back in. fired up, removed the uconnect 7 setting from the BCM, and did a proxy align. then i went through all the modules clearing the myriad codes. did another proxy algin and checked for errors, which there were none.

but here is the success part: whatever happened to the canbus and proxy config, suddenly his speedometer was accurate again. like dead on for his tire size.

anyway, i just wanted to share my experience changing the tire size on a renegade to correct the speedometer. i hope you tweakers and hackers out there find this useful. if you need to fake a sleep cycle. pull a can bus module like the radio, do a proxy align without it, put it back, and do a proxy align. wahlah... sleep cycle
 

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This sounds like a very interesting, if frustrating, experience. Since I'm still fairly new to Renegades, can you please explain this "proxy alignment" procedure? I have alphaobd, but have only used it on my old '06 Magnum and '14 Ram which are very different. Thanks.
 

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This sounds like a very interesting, if frustrating, experience. Since I'm still fairly new to Renegades, can you please explain this "proxy alignment" procedure? I have alphaobd, but have only used it on my old '06 Magnum and '14 Ram which are very different. Thanks.
there are a couple of posts on the renegade forum about this, but i will try to give you an explanation as i understand it.

cars these days do not just have one computer. they have dozens or more. these computers talk with eachother on a built in network called the CANbus network . (CAN has meant many things, but generally accepted is Controller Area Network as opposed to a LAN or a WAN you might have in your house)

the CAN network is made up of nodes and endpoints. nodes talk to end points and end points are what you can interact with. the instrument cluster is an endpoint, the radio, the 4 wheel drive, the engine, etc. the engine endpoint may control dozens of computers inside the engine itself, but they all get info from and provide info to the ECM (engine control module end point).

each endpoint has a configuration called the proxy configuration, some times written proxi. (i don't know why it is called this... i just know it is). this is just a binary file that lists what is in the car.

the main, overreaching computer in the car that determines what features are present and what are not is the BCM, or Body Computer Module... this includes what modules/endpoints are in the car and their address, and features like what the trim level is, what the type of remote you have is, etc.

parts of the proxy configuration are stored on all the endpoint computers. this is mainly this is so all the devices know how to talk to each other. when a device is added to the canbus it generates a psudo-random address and broadcasts messages to all the other devices. the address is saved so all the devices know what messages are coming from where. if you add a device and the address is unknown, you will get error codes about a proxy configuration issue. the other tell-tale sign in the renegade is the flashing odometer. under normal circumstances you should not have any sort of proxy config error, so the idea (i think anyway) was to warn the driver to get their vehicle to the shop for service. the Check engine light has become synonymous with a pollution control issue, and they wanted something to stand out.

to complicate matters further, the renegade has CANbus networks. 1 low speed and 2 high speed. this is why you see people talking about the "adapters" to interface with them. for the renegade there is the "blue" adapter and the "grey" adapter. other fiat/alfa/chrysler products use yellow, purple, green, and red depening on which network you want to interface with. to access these networks you use the ODBII diagnostic port in the car. CARB standardized the odbii port and the protocols used so all cars in California could be quickly accessed with out any special equipment for pollution testing. because the California market is so big it quickly became a world-wide standard. but they only specify a couple of pins on the connector as to what they are supposed to do. manufacturers were free to use the free pins for whatever they wanted. ford, chevy, chrysler, tesla, bmw, etc all use the other pins for manufacturer specific control. it is much easier to do software updates through the ODBII port then to have to find some burried connector on the transmission that is probably covered in junk.

modules on vehicles go bad. bad transmission are replaced, radios are replaced, etc. or the dealer adds an factory option like towing before the vehicle is sold. there is a procedure that is covered in the service manual to do all this. generally it goes:
1) module is added/replaced
2) BCM is updated to reflect the new features if there are any
3) the BCM generates a proxy configuration
4) a proxy allignment is performed so all current computers know what the new device is and how it talks to them
5) dtc codes are reset

the dealer has a computer to interface with the renegade that doesn't require any adapters. it also does not directly interact with the proxy configuration file. the dealer uses sales codes. basically there is a list of codes that go into each and ever renegade. they are dependent on what is offered that year. there is a code for the sun roof, a code for lane departure, a code for beats audio, etc. their system makes it safe so that they can only add sales codes that were available for that year renegade. this feature is designed so they cannot accidentally put in a ABS module from the wrong year that doesn't know how to communicate properly with the rest of your car, creating a serious safety problem.

we are not the dealer. so we don't have their really expensive software. but we do have alfaobd. alfaobd allows us to directly interact with the proxy configuration and all of the endpoint computers. it allows you to add features (window down from key fob), disable things (seat belt warning), and test function (instrument panel). unfortunately it is a lot more rudimentary then the dealer software. it lists a lot of "known" options that are contained int the proxy config, that don't necessarily exist or work in your vehicle. it is important to keep a current back up of your proxy config before making changes.

so you may ask, why do they do this in the renegade? in a dodge, or a jeep wrangler, there is no proxy alignment needed for most changes. you make the changes and it just works. in my opinion it is because the renegade is a European spec vehicle. in Europe, people don't change their tire size... what comes on the vehicle comes on the vehicle. from what i have read on other forums, service work is 99% performed by the manufacturer for vehicles like this. its part of the culture. it was not designed to be a "wrangler-lite". it was designed to compete with other small commuter vehicles available in their markets. Fiat offers the 500x which uses the same frame as the renegade, but it also uses a lot of the same modules including BCM. the whole proxy aligning business is because of the modules it uses. wranglers, dodge 2500's, Chryslers, all use different BCM's that aren't speced with the European market as being its primary home.

just one more thing... this is all how i understand it. i could totally be wrong, or misguided on certain points, and i certainly take constructive criticism. i have read a ton of message boards, talked with people who have done things with their renegade, talked with the developer of alfaobd, and messed around with my own vehicle. i think i have a pretty good grasp of how it all works together. i have a passion for reverse engineering propriety systems like this, at least in a "big picture" kind of way. i hope my explanation helps you understand a little bit more too.
 

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Discussion Starter · #4 ·
This sounds like a very interesting, if frustrating, experience. Since I'm still fairly new to Renegades, can you please explain this "proxy alignment" procedure? I have alphaobd, but have only used it on my old '06 Magnum and '14 Ram which are very different. Thanks.
oh! i just realize i forgot the procedure... with alfa obd it is easy. depending on your odb2 interface you need1 or 2 adapter cables. if you have the ODBlink MX+ you only need the grey cable. if you have other interface you need the blue adapter as well. basically the adapter takes your interface and connects the CAN pins to the right pins on the interface.

this is the short short version of the procedure. there are others who have writen comprehensive ones about which icon to use in alfaobd. if you need them i encourage you to use google to look. really it is not that hard to do, just go slow and read everything as you go. it goes something like this:

1) start alfaobd and connect your interface
2) connect to the BCM module for the renegade
3) click the icon at the bottom for active diagnostics (car with its hood up)
4) in the drop down go to proxy tools
5) select option backup proxy config and click start. this will save a working version of your current proxy config if you ever need to go back
6) back to the main drop down and choose PROXY Alignment. make sure you have your grey and blue adapters in hand. do not make any changes or start an alignment without the adapters. you will have a bad time.
7) click start ONCE. some times it takes a second to go to the next screen.
8) it will build a proxy configuration. you can review it and then click "NEXT".
9) alfaobd will send each module in turn a message saying they are going to receive a new proxy configuration. the module will receive the proxy config, write its important bits to memory and return either "success" if it was success" or "failure" if it wasn't.
10) if the write was a success, it will move on to the next module. if the write was a failure, it will keep the old configuration, and then move on to the next module. this will cause DTC codes.
11) at a certain point, it will want to write the proxy config for the radio and hvac. alfaobd will stop and tell you
a) turn off the car.
b) unplug your odb interface
c) plug in the BLUE adapter
d) plug your interface into the adapter
e) turn on the car. wait for all the errors to clear on the instrument cluster. they are usually scary errors about the brakes and power steering not working. they are all because of the proxy mismatch and you should not concern yourself
f) when the errors clear you click "ok" on the screen
12) alfaobd will reconnect to the car on the first high speed canbus for the radio and the hvac and things like lane departure if you have them.
13) a couple more modules later you will get the same message about shutting off the car and using the grey adapter.
a) turn off the car.
b) unplug your odb interface
c) plug in the BLUE adapter
d) plug your interface into the adapter
e) turn on the car. wait for all the errors to clear on the instrument cluster. they are usually scary errors about the brakes and power steering not working. they are all because of the proxy mismatch and you should not concern yourself
f) when the errors clear you click "ok" on the screen
14) again, more scary messages but it will now write to the ABS, power steering, and airbag modules.
15) when it completes it will tell you to turn off the car and turn it back on.
16) usually i turn off the car, disconnect the grey adapter and plug my interface back in before turning the car back on.
17) it should start up and you should have no error messages on the dash. connect with alfaobd and check the bcm. reset any codes generated from the proxy mismatch when you turned it off twice. they are stored and not active, but they will not clear themselves.

if you get a failure you have to figure out why. first it could be because there is an active or pending DTC code in the module. try connecting to that module with alfaobd and cleaing the codes before doing a proxy align it could also be because you are trying to write the wrong data (my tire size over 2499). or you are trying to add a feature that doesn't exist for your car (like navigation mirroring, so navigation shows up on your instrument cluster as well as the radio screen). this is why it is important to keep a backup of your config, and to make only one change at a time. if it fails it is easy to roll back. it seams like a super big pain in the butt, as it takes 3 or 4 minutes to perform a proxy alignment, but it really is the safer way to go.
 
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