can you help on this error code C21A909 for the Radar Module -Front center (MRR)???
It appeared after a front window replacement - and since caused issues (=fully down) of front collission assitant, lane assist, traffic light status indication
DTC report after my recent FCM calibration attached: ECU resets of FCM+Hydra+MRR, finished with a deep sleep . Software versions as well (MRR doesn't show up there)
Is it rather
a) a calibration issue?
or
b) a connection issue of wires/plugs (e.g. water in a plug; or simply plug was disconnected in a repair, but not properly reconnected)?
or
c) even a module hardware failure?
or maybe something completely different?
The interesting thing is that after calibrating the FCM with Freesker tool, the front collission assistant (including braking in close situtations), the lane assist, the traffic light status indicator started working again - so I was wondering how a front collission assistant incl braking could work without the Front center radar module, i.e. I think this module does work actually.
Nevertheless, these warning symbols keep on shining, and the error code C21A909 still remains :-(
Any hint and recommendation what to do next?
Thank you so much in advance!
(26.07.2026, 17:50)secretname@gmx.de Wrote: Dear Freesker Support, or any other expert on the radar system:
can you help on this error code C21A909 for the Radar Module -Front center (MRR)???
It appeared after a front window replacement - and since caused issues (=fully down) of front collission assitant, lane assist, traffic light status indication
DTC report after my recent FCM calibration attached: ECU resets of FCM+Hydra+MRR, finished with a deep sleep . Software versions as well (MRR doesn't show up there)
Is it rather
a) a calibration issue?
or
b) a connection issue of wires/plugs (e.g. water in a plug; or simply plug was disconnected in a repair, but not properly reconnected)?
or
c) even a module hardware failure?
or maybe something completely different?
The interesting thing is that after calibrating the FCM with Freesker tool, the front collission assistant (including braking in close situtations), the lane assist, the traffic light status indicator started working again - so I was wondering how a front collission assistant incl braking could work without the Front center radar module, i.e. I think this module does work actually.
And another interesting thing about the diagnosis of the MRR: when running first time, there's a timeout. When refreshing/running again, it is successful. I was wondering whether this points to an issue with connecting to it. See the last 3 pictures attached
Nevertheless, these warning symbols keep on shining, and the error code C21A909 still remains :-(
It could either be a hardware defect in the front center MRR, or the connection might not be establishing due to a loose cable.
For now, please check whether you’re receiving a DTC log for the MRR and feel free to send us the DTC report here. In any case, I would recommend performing a hard reset first and then checking the DTC report for the MRR.
thanks for responding so quickly.
I did what you asked to do:
1. ran the DTC report, see report (1).pdf
=> active fault for Radar Module -Front center (MRR) - Component Failure withDTC Code: C21A909 and DTC Status 0x09
=> MRR Midrange radar module0 faults 2. ran the software version check for MRR: failed, OS unknown
3. I hard reset the Hydra and the MRR
4. then let deep sleep
5. ran the DTC report again, see report (2).pdf
=> same as in step 1., i.e. active fault for Radar Module -Front center (MRR) - Component Failure withDTC Code: C21A909 and DTC Status 0x09
but: => MRR Midrange radar module(failed), see MRR software check 1 (before reset and deep sleep).jpg
6. 3. I hard reset the Hydra and the MRR again
7. simply ran the DTC report again, see report (4).pdf
=> active fault for Radar Module -Front center (MRR) - Component Failure withDTC Code: C21A909 and DTC Status 0x09 (DTC failed at the time of request)
=> MRR Midrange radar module0 faults 8. ran the software version check for MRR: surprisingly it now was showing the software version
What I also noticed is that in the scripts for MRR, the button Read SEC_OC is active dark blue, but there is a red X right next to the "Read SEC_OC" => what does that mean?
(file Scripts for MRR_Read SEC_OC - failed.jpg)
To me it looks as if the MRR does respond occasionally - maybe there's a timeout issue?
Still all the time the red error symbol for the ADAS is on / won't get off, but again, the Front collission assistant with active breaking does work all the time (and isn't that one using the Radar Module -Front center (MRR) module?)
Any more idea about a procedure / what to do next - what would you recommend?
My thought: Is there a function to fully teach-in and re-calibrate this Radar Module -Front center (MRR) module fully freshly?
If that doesn't work simply replace that piece of a hardware module by a new one, with checking/replacing any connector with it. The main connector in the front right area in front of the wheel (the grey one) has already been fully replaced - it was really corroded (known Fisker Ocean bad engineering issue with water from windscreen spilling all over it continuously)
THANKS AGAIN FOR YOUR ADVICE - always highly appreciated!
There is a sufficiently high probability that this is a potential hardware issue.
Please perform the following steps:
- Write the VIN to the MRR Front Center.
- Write the SecOC.
- Perform a hard reset.
- Allow the vehicle to enter sleep mode completely.
- After the vehicle has completed the sleep cycle, send us the DTC report for the MRR Front Center only.
Once we receive the DTC report, we will continue with the analysis.
[quote pid="141" dateline="1785703017"]
Hi Freesker Support,
tried to follow your instructions, but Write VIN to the MRR is not possible, since button is inactive (screenshot 1).
I tried to read the VIN - 2 times unsuccessful (screenshot 2), but after an ECU reset and a deep sleep, I think a quick green check mark appeared - so I guess successful at least once.
Then I did the Tester Alive, and that worked (screenshot 3).
The strange thing is still, when I run the error check for the MRR once, it says timeout (screenshot 4). When I refresh it runs, and says "0 faults" (screenshot 5)
1 week ago, I also ran the "Write Role", and it was successful.
Very confusing to me.
Still I believe there is a timeout issue with the MRR. Sometimes it works (also the active front collission warning and braking), sometimes not. Due to these occasional failures I think the red ADAS warning symbol is always on.
Do you have any more idea how to Write VIN as you requested? Any chance you can activate that button for me?
Or any other procedure to do?
Dear Freesker Support,
Please allow another friendly reminder.
Would you please advise what to do next?
„ - Write the VIN to the MRR Front Center“ step no. 1 in your last procedure could not be executed simply because this button is inactivated in my Freesker Pro diagnosis tool.
Best regards
Daniel