[virtualizationg]

I had my car hit and the body shop replaced the driver side door. After picking up the car I have had lights for ABS and Traction Control. When I plugged in my code reader I see codes P127E and then "480964 DEX under voltage at Control Unit" as well as 4809AB "DSC undervoltage in vehicle". When I took it to the dealership I was told it was all from my AFE Scorcher so I uninstalled it knowing that wasn't the issue. I have researched over the last two weeks and seen everything from change my plugs and coils plus the battery, replace the turbo boost sensor to buy a 2K ABS module. The car also has a drivetrain malfunction light and hardly any power. Gas mileage down to 17 MPG on Highway.


The car is a 2013 BMW 328i Xdrive with the N26 2.0 Engine

[Billfitz]

I got a dash warning for an ABS failure. A minute later a chassis stabilization warning came up, then the cruise control wouldn't work, finally my spoiler was declared non-functional. I feared the next thing would be limp mode.

A bit of searching on line pointed to the likelihood of a speed sensor on a wheel being the cause, since the ABS and all the rest need to have speed information from all the wheels to function. I even found a few videos on how to diagnose the problem with my Foxwell.

I did a scan, and all of the faults came up, the first traced to the left rear speed sensor. It said the problem was intermittent. I cleared the codes and all the dash warnings went away. I did an operational test of the speed sensors and they were all working. I took a drive, no new warnings. If the problem comes back I'll order a new speed sensor, changing them is easy.

This might have nothing to do with your problem, but it's worth checking out.

[virtualizationg]

Thanks for the response. So I bought a foxwell 624 Pro and was able to reset the lights but they come right back on. I was able to monitor the speed sensors on each wheel and they seem to be very close in speed. I say seem because it was tough to be 100% focused when driving

I contacted Foxwell and they don't have the ability to tell you which sensor, if any, are alerting. I have been searching the net for something that would before I start wholesale replacing parts to find out the problem. I very much appreciate your reply and help.

[Billfitz]

Originally Posted by virtualizationg

I was able to monitor the speed sensors on each wheel and they seem to be very close in speed. I say seem because it was tough to be 100% focused when driving

The speed sensors either work or they don't, so there's no need to test them on the road. I tested mine in my driveway, they only need at least 1 MPH to give a reading. Maybe your 624 is different from my NT 510, which did pin down the incident that tripped the fault code, in my case, to the left rear wheel sensor. It also showed it to be intermittent, so it knew that the condition that tripped it went away on its own. If you cleared the codes and they came back again it means whatever the fault is still exists.
The thing about the codes is that there's a domino effect. Mine showed codes for ABS, chassis stabilization, cruise control failure, spoiler failure and the dreaded 'Drive Train Malfunction, Go Directly to Dealer'. But I didn't actually have five failures, I only had the one, the ABS sensor. The ABS sensors provide wheel speeds to not only the ABS module but to all those other functions as well. Without the speed information from the ABS sensors none of them will work. In your case if you're getting an ABS warning but the speed sensors are OK then something else might be at fault that also renders the ABS inoperative. Google every possibility, chances are it's happened to someone else and their experience is documented. That's how I knew what to look for in my case.

[upsidedownfunnel]

How soon after you picked up your car did you get the lights? You should take your car back to the body shop. If you had it repaired through insurance, you might be able to get them to help you out. Most likely this is something the body shop would have to fix though. They might have just damaged something while they were replacing your door.

[virtualizationg]

So at this point I am changing the battery (it is 6yrs old) as its time, plugs and coils. Once that is done and I register the battery I am hoping the voltage codes will go away. Wheel sensors all test good.

[virtualizationg]

I replaced the battery and registered it, replaced the plugs and coils with OEM replacements. Car runs like new. Still have a P127E permanent code stored and the ABS lights on. Only error is stating "DSC voltage low at unit"

[hmmwvj]

Originally Posted by Billfitz

The speed sensors either work or they don't, so there's no need to test them on the road. I tested mine in my driveway, they only need at least 1 MPH to give a reading. Maybe your 624 is different from my NT 510, which did pin down the incident that tripped the fault code, in my case, to the left rear wheel sensor. It also showed it to be intermittent, so it knew that the condition that tripped it went away on its own. If you cleared the codes and they came back again it means whatever the fault is still exists.
The thing about the codes is that there's a domino effect. Mine showed codes for ABS, chassis stabilization, cruise control failure, spoiler failure and the dreaded 'Drive Train Malfunction, Go Directly to Dealer'. But I didn't actually have five failures, I only had the one, the ABS sensor. The ABS sensors provide wheel speeds to not only the ABS module but to all those other functions as well. Without the speed information from the ABS sensors none of them will work. In your case if you're getting an ABS warning but the speed sensors are OK then something else might be at fault that also renders the ABS inoperative. Google every possibility, chances are it's happened to someone else and their experience is documented. That's how I knew what to look for in my case.

I appreciate the detailed answer. I have the exact problem you did. I identified the sensor and cleaned it (was wet for some reason). The codes appeared a few times but disappeared a few miles later and haven't shown since.

At this point I'm wondering if the sensor really works. Do you know if a faulty sensor could somehow be reported as working, resulting in no codes showing?

Also, assuming I had a faulty sensor previously and a good one on now, do you know if codes will keep showing until I clear them, or will the car just know about the new sensor?

TIA!