Service Power Steering & DTC U0121
07-12-2015, 02:42 PM
#1
Burning Brakes
Thread Starter
Service Power Steering & DTC U0121
Ok, I had the car out last night and as I was approaching a stop light I received the message "Service Power Steering Drive With Care" on the dash. At this point, the power steering was gone. I pulled over and stopped and restarted the car and power steering still gone.
I got home and hooked up HP Tuners and received another code of U0121 - Lost Communication with Anti-Lock Brake System (ABS) Control Module (Pending) (History) (Current) (Immature). I cleared the code and shut the car down, but upon restart it came back immediately.
I left it alone and figured I'd call the service department on Monday. I head back in the garage later in the evening when it was completely dark and noticed the entertainment screen flickering/flashing as if something was cycling every so many seconds. It appears as though something is trying to cycle through and shut down and can't. I disconnected the battery at this point to prevent draining it.
Has anyone had any experience with this? The first dash issue I've read most needed a steering rack replacement and that solved the issue. Mine is an M7 and VIN 8808. I haven't seen anything on the second issue. I'm looking for information to determine if this is something that will require a computer reflash that will wipe out my tune so that I can notify the technician of my mods and the fact that the car is tuned and sitting full of E85. This way we can get the tune file back in the car before they test drive it after repair to avoid any other mishaps.
I will say that parking one of these suckers on the wide tires and backing into the driveway and garage was quite a workout.
I got home and hooked up HP Tuners and received another code of U0121 - Lost Communication with Anti-Lock Brake System (ABS) Control Module (Pending) (History) (Current) (Immature). I cleared the code and shut the car down, but upon restart it came back immediately.
I left it alone and figured I'd call the service department on Monday. I head back in the garage later in the evening when it was completely dark and noticed the entertainment screen flickering/flashing as if something was cycling every so many seconds. It appears as though something is trying to cycle through and shut down and can't. I disconnected the battery at this point to prevent draining it.
Has anyone had any experience with this? The first dash issue I've read most needed a steering rack replacement and that solved the issue. Mine is an M7 and VIN 8808. I haven't seen anything on the second issue. I'm looking for information to determine if this is something that will require a computer reflash that will wipe out my tune so that I can notify the technician of my mods and the fact that the car is tuned and sitting full of E85. This way we can get the tune file back in the car before they test drive it after repair to avoid any other mishaps.
I will say that parking one of these suckers on the wide tires and backing into the driveway and garage was quite a workout.
07-12-2015, 05:52 PM
#2
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Member Since: Jan 2006
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St. Jude Donor '14-'15
From what you're describing, it sounds like the BCM may be faulty. It will depend on what DTCs are stored to determine which module is at fault, but that screen flickering indicates the system is staying engaged and looping past the battery cutoff. The ABS module isn't able to cause that, so we have to start backtracking.
The E92 (ECU/ECM) is certainly going to be scrutinized when pulling the DTCs from GDS, and assuming it's not replaced (whether as part of the problem or simply out of diagnostic evaluation), I would expect it (and all other subsystems) to be re-flashed as part of the normal diagnostic procedure.
The failing subsystem will leave a long trail of DTCs that show up in GDS, so you can usually see exactly what's causing something like this. The good news is that, from what I can tell by this short description, your tune is most likely not the culprit.
The E92 (ECU/ECM) is certainly going to be scrutinized when pulling the DTCs from GDS, and assuming it's not replaced (whether as part of the problem or simply out of diagnostic evaluation), I would expect it (and all other subsystems) to be re-flashed as part of the normal diagnostic procedure.
The failing subsystem will leave a long trail of DTCs that show up in GDS, so you can usually see exactly what's causing something like this. The good news is that, from what I can tell by this short description, your tune is most likely not the culprit.
07-12-2015, 06:43 PM
#3
Pro
From what you're describing, it sounds like the BCM may be faulty. It will depend on what DTCs are stored to determine which module is at fault, but that screen flickering indicates the system is staying engaged and looping past the battery cutoff. The ABS module isn't able to cause that, so we have to start backtracking.
The E92 (ECU/ECM) is certainly going to be scrutinized when pulling the DTCs from GDS, and assuming it's not replaced (whether as part of the problem or simply out of diagnostic evaluation), I would expect it (and all other subsystems) to be re-flashed as part of the normal diagnostic procedure.
The failing subsystem will leave a long trail of DTCs that show up in GDS, so you can usually see exactly what's causing something like this. The good news is that, from what I can tell by this short description, your tune is most likely not the culprit.
The E92 (ECU/ECM) is certainly going to be scrutinized when pulling the DTCs from GDS, and assuming it's not replaced (whether as part of the problem or simply out of diagnostic evaluation), I would expect it (and all other subsystems) to be re-flashed as part of the normal diagnostic procedure.
The failing subsystem will leave a long trail of DTCs that show up in GDS, so you can usually see exactly what's causing something like this. The good news is that, from what I can tell by this short description, your tune is most likely not the culprit.
I've gotten a Service Rear Axle message - the shop grabbed a DTC C0414 & U0428 - both codes end up being undetermined - they replaced the fluid but the Service Rear Axle message and associated erratic StabilTrack behavior is still there
It seems after maybe 20+ miles of warm up causes the Service Rear Axle message to appear, at which point I lose Competitive Driving Mode & Performance Traction Management (while in Track Mode), and cannot renter it - also, while in Sport Mode, I am unable to disable StableTrack, which is truly nessasary to do as it actenutes almost immediately entering a turn, best described as hypersensitivety
As per the owners manual, the Service Rear Axle message indicates "irradic StabilTrac behavior"...
My only question is, does anyone know what is causing the Service Rear Axle message, so I can give my shop some help - they simply do not know what to do
Last edited by Rd16rr; 07-12-2015 at 06:46 PM.
07-12-2015, 07:44 PM
#4
Burning Brakes
Thread Starter
From what you're describing, it sounds like the BCM may be faulty. It will depend on what DTCs are stored to determine which module is at fault, but that screen flickering indicates the system is staying engaged and looping past the battery cutoff. The ABS module isn't able to cause that, so we have to start backtracking.
The E92 (ECU/ECM) is certainly going to be scrutinized when pulling the DTCs from GDS, and assuming it's not replaced (whether as part of the problem or simply out of diagnostic evaluation), I would expect it (and all other subsystems) to be re-flashed as part of the normal diagnostic procedure.
The failing subsystem will leave a long trail of DTCs that show up in GDS, so you can usually see exactly what's causing something like this. The good news is that, from what I can tell by this short description, your tune is most likely not the culprit.
The E92 (ECU/ECM) is certainly going to be scrutinized when pulling the DTCs from GDS, and assuming it's not replaced (whether as part of the problem or simply out of diagnostic evaluation), I would expect it (and all other subsystems) to be re-flashed as part of the normal diagnostic procedure.
The failing subsystem will leave a long trail of DTCs that show up in GDS, so you can usually see exactly what's causing something like this. The good news is that, from what I can tell by this short description, your tune is most likely not the culprit.
I've been VERY fortunate to have this be my first issue with a Corvette while it's still under warranty so the process is new to me. And I even had an 05 C6!
. Luckily my past issues were bug fixes with mods where I created the problem and needed to work thru it. As usual, thanks Theta for providing a high level diagnostic interpretation of what may be going on.
08-04-2015, 03:01 PM
#5
Burning Brakes
Thread Starter
I just wanted to follow up on this in the event someone else experiences the same issue. I took my car into the dealer yesterday and had a discussion with the Corvette Tech including listing out my current mods so he was aware of what has been done to the car. He hooked the scanner up and there were a ton of codes thrown so he said he'd dig in and get back to me.
He called later in the afternoon and the root cause of my issues.....the freaking catch can! What happened was the can rattled slightly loose. The can (UPR) is mounted on top of a ground. So what happened was the ground wasn't closing the loop and threw a code on the Power Steering module. I guess this feeds into the other systems as they all talk to each other now and that created a host of other issues....exhaust valves forced shut, driving modes unable to change, ABS issues, hill assist brake functions disabled, and on and on.
He sanded the paint under the ground and tightened the bolt and cleared the codes and it solved all the issue. There ended up being no mechanical failure in terms of the rack itself. It looks like I'll be looking for another mounting location for the can or another alternative can.
Good news is she's back on the road. Bad news is its a little scary something so small can interact with so many different things and cause so many issues.
He called later in the afternoon and the root cause of my issues.....the freaking catch can! What happened was the can rattled slightly loose. The can (UPR) is mounted on top of a ground. So what happened was the ground wasn't closing the loop and threw a code on the Power Steering module. I guess this feeds into the other systems as they all talk to each other now and that created a host of other issues....exhaust valves forced shut, driving modes unable to change, ABS issues, hill assist brake functions disabled, and on and on.
He sanded the paint under the ground and tightened the bolt and cleared the codes and it solved all the issue. There ended up being no mechanical failure in terms of the rack itself. It looks like I'll be looking for another mounting location for the can or another alternative can.
Good news is she's back on the road. Bad news is its a little scary something so small can interact with so many different things and cause so many issues.