Rotated tires-codes u0121 & u0155 show up
 

Rotated tires this weekend, next time car is turned on I get these 2 codes from my scangauge2. Cleared them once but they come right back on..what the heck did I do to cause this??

U0121 Communication error to ABS HU/CM
U0155 Communication error to instrument cluster


I'm guessing you have bumped a connector when you rotated the wheels/tires. Go check all corners and see if you can find one that is loose. 2nd code I'm not sure about that one.

Did you plug in the Scanguage before or after the car was started? Sometimes it doesn't like being plugged in afterwards. Just a thought.

Mazurfer, thanks for the reply. The scangauge is always plugged in and hasn't caused any issues so far.
I will check the ABS sensors tonight to see if I disconnected one somehow.

Only thing I can think of. Both those codes you mentioned are universal codes, so more difficult to figure out. They could go away after a drive cycle or two??????

U codes are actually module to module communication codes. If those codes are stored in the PCM part of the memory and come right back that means your car is having communication interrupted between the PCM and the ABS module and between the PCM and the I/C. hardest codes to trace back most of the time. ill try to find the graph later, your CEL isnt on tho and no other lights are on either, correct?

kevin.

You're right Kevin..........and my own history with the Scangauge says that sometimes if that connection is loose to the ODB II port, it can report funny codes itself.

I do have a CEL and the Traction Control 'Skid" light both on. I should have reported that earlier.

Turn car to on, but don't start. Turn wheel all the way to the right and then all the way to the left.
Shut car off.
Then start it and tell us what is on. Don't forget to not shut it down cold!

Oh......................and when you do start it again, go ahead and clear the codes and then scan it again.

OK, thanks for the input. It will be a while, I'm at work.

Mazurfer, followed your instructions and it has fixed the CEl. Turning the wheels lock to lock got rid of the traction control light, when I started it, the CEL was still on. Same 2 codes. Cleared them with the Scangauge and drove it...no lights!

Thanks for your help.

Hopefully it will stay that way.
FYI..............not that you did it, but anytime you unhook the battery, you will have to do that TCS/DCS reset.
The codes......who knows.......might have been just one of those things?

codes normally set when the terminals are yanked, but generally should clear automatically without setting a CEL, and generally when erased they won't reoccur as once the terminals attached their communication is working. may be my unfamiliarity with scangauge or whatnot.

kevin.

This is weird. The same codes just came up for me after changing my thermostat? I guess I'll see if they comeback. Maybe the Scangauge doesn't like to be connected when the battery is disconnected and reconnected?

it's possible, if we leave our IDS systems connected, or the key on, and yank the terminals then reconnect the battery and check codes most systems will report U-codes because they dont know the battery was disconnected all they know is 2 seconds ago they could converse with each other and then they couldn't. Like i said though, they normally wipe themselves next key cycle, most of the time a stored U-code with absolutely no side effects noticeable in that system is a "ghost code" (happens at least on all mazdas, dunno about other makes) and doesn't trigger a CEL, i'm thinking something in the scangauge's are confusing the car in some way, pure speculation tho.

kevin.

I also got the U0155 from un balanced tires because of age.

Hate to revive an oldie, but I just got a U0121 ... Going to wait a few days to see if it goes away.

I have a similar problem to and i could really use everyone's help.
 

Not to long ago i had my rx8 checked by autozone because my engine light turned on and well these are the 2 codes i got from the diagnostics P0302 and U0155. The P0302 indicates that cylinder 2 had detected a misfire of excess emissions level. As for U0155 it states that it lost communication with instrument panel cluster (IPC) control module. Whats is the problem, what does it mean im in drier need of help. I dont want to damage my car my baby anymore than it already is.

I have read a lot of posts, but have not seen one that resembles my situation. While driving my ABS, Brake and Stearing light illuminate. Along with this the speedometer reads 0 (zero) and the steering is tight. I have disconnected the battery and made sure the posts are clean. I have completed all reset functions listed in numerous posts. The one thing that seems to clear the lights is while in park, revving the engine above 3k for a couple of seconds. Although, this is temporary. Had the codes read and listed U0121, lost comm with ABS system. Any thoughts?

Start tracing the wiring harness from the ABS back to the ECU, AND verify the wiring to the ABS sensors on each wheel. The issue is there somewhere. I believe (but not certain) that the speedometer gets its info from the abs/wheel speed sensor, which means that if that sensor's signal, or the whole ABS connection was interrupted, the speedo would show 0, the car would assume something is wrong and trip the brake, stability control and steering lights.

Hello, I have 2 RX8 and both have the same problem. Did you managed to fix it? Tried changing the alternator but not helping.

Are you sure it's not a scanner issue? For 2 cars to have the same U codes is unlikely without it being something to do with the scanner

What kind.of scanner is it?

Thanks for your reply. Are you suggesting that the scanner i used is causing the ABS and power steering problem? Actually both my cars are using OBDII gauge to display water temperature, and can also scan and clear codes. I kind of suspected the same, but the problem remained even with the gauge disconnected. I also tried using Torque with bluetooth obd2 scanner, and it returned the same code. Could the OBD2 gauge has caused permanent damage to my ABS and power steering control module?
https://cimg6.ibsrv.net/gimg/www.rx8...5861fbbb3c.jpg

I replaced the anti-lock brake controller. Mine is not a traction controller. I purchased it off ebay. Be sure to keep the old device and take your RX8 to the dealer and have the old and new devices tuned for the ECU.

Turned out to be the anti-lock controller

Thanks. Really wonder why both car's ABS decide to go south at the same time.