Mazda 2 from 2008 - Error code U0121 "Lost communication with ABS Control Module"
#1
11-10-2022, 03:28 PM
Mazda 2 from 2008 - Error code U0121 "Lost communication with ABS Control Module"
Hello everyone
I have a Mazda 2 from 2008,(DE_, DH_) 1.3L (75HP). I was getting it ready for inspection over a period of 2 months where things like the whole back axle were changed, the front left wheel bearing and anchor plate as well as the back left coil spring and 2 shock absorber sleeves in the front. I finally finished everything up yesterday and as soon as I drove out of my driveway the DSC and ABS light came on and weren't able to accelerate, after braking to a full stop and throttling a little bit the handbrake light came on and stayed on but now I was able to drive perfectly normal but with all 3 said lights illuminated at the same time. It seems like the ABS is being disabled as soon as you start driving a little bit cause if you turn off the car and drive again, only the DSC and ABS are illuminated which means that the ABS works until the handbrake light turns on, then it automatically disables the ABS and then you can drive normally but without ABS. I've test-driven it and it drives and brakes perfectly fine.
I've checked ALL fuzes in the car both in the engine compartment and also the little module to the left of the steering wheel, and none of them were bad. I've tried 5 different OEBD scanners and no error codes come up unless you remove the fuze for the DSC and ABS and turn on the car, then the check engine light comes and it gives me the above error code U0121 - "Lost communication with ABS Control Module".
I've of course tried looking for any bad wiring, but I just can't seem to find anything. I really don't believe that an ABS module can just go bad from one day to another. I drove in the car 2 weeks before I did the main fixing on it e.g. changing the back axle and fixing the rust, and now it's telling me that there's no communication with the ABS Module or that the OEBD scanner can't communicate with it. I've checked pins 6 and 14 on the CAN bus (OEBD) connector and they both read 2.5 Volt as they should
I did some welding on it because of rust, but I did indeed disconnect the minus on the battery so that it doesn't short anything
Do you think that the welding could've shortened something related to the ABS Control Module?
Do you have any suggestions on what I can do? Any experience with the same error code and what you can do to check the ABS Control Module circuit, it's so hard to find where those wires go.
Does anyone happen to have a Mazda 2 2008 service manual or maybe even the wiring diagram for the ABS Control Module cause I haven't yet checked the wiring and the connectors going into the module with a volt meter?
Thank you so much for any help related to this. I'm awfully sorry for the long read!
//Anton
I have a Mazda 2 from 2008,(DE_, DH_) 1.3L (75HP). I was getting it ready for inspection over a period of 2 months where things like the whole back axle were changed, the front left wheel bearing and anchor plate as well as the back left coil spring and 2 shock absorber sleeves in the front. I finally finished everything up yesterday and as soon as I drove out of my driveway the DSC and ABS light came on and weren't able to accelerate, after braking to a full stop and throttling a little bit the handbrake light came on and stayed on but now I was able to drive perfectly normal but with all 3 said lights illuminated at the same time. It seems like the ABS is being disabled as soon as you start driving a little bit cause if you turn off the car and drive again, only the DSC and ABS are illuminated which means that the ABS works until the handbrake light turns on, then it automatically disables the ABS and then you can drive normally but without ABS. I've test-driven it and it drives and brakes perfectly fine.
I've checked ALL fuzes in the car both in the engine compartment and also the little module to the left of the steering wheel, and none of them were bad. I've tried 5 different OEBD scanners and no error codes come up unless you remove the fuze for the DSC and ABS and turn on the car, then the check engine light comes and it gives me the above error code U0121 - "Lost communication with ABS Control Module".
I've of course tried looking for any bad wiring, but I just can't seem to find anything. I really don't believe that an ABS module can just go bad from one day to another. I drove in the car 2 weeks before I did the main fixing on it e.g. changing the back axle and fixing the rust, and now it's telling me that there's no communication with the ABS Module or that the OEBD scanner can't communicate with it. I've checked pins 6 and 14 on the CAN bus (OEBD) connector and they both read 2.5 Volt as they should
I did some welding on it because of rust, but I did indeed disconnect the minus on the battery so that it doesn't short anything
Do you think that the welding could've shortened something related to the ABS Control Module?
Do you have any suggestions on what I can do? Any experience with the same error code and what you can do to check the ABS Control Module circuit, it's so hard to find where those wires go.
Does anyone happen to have a Mazda 2 2008 service manual or maybe even the wiring diagram for the ABS Control Module cause I haven't yet checked the wiring and the connectors going into the module with a volt meter?
Thank you so much for any help related to this. I'm awfully sorry for the long read!
//Anton
#2
11-19-2022, 11:17 AM
Not exactly an answer to everything: " I really don't believe that an ABS module can just go bad from one day to another" - I think they can. I have had it happen on 2007 Fiesta and 2009 Focus both belonging to my brother but he always gets me to fix things for him. I think Mazda 2de abs is same as fiesta abs, it looks the same and is in exact same position on the bulkhead.
Could MIG welding damage it? - years ago I always disconnected both battery terminals. After welding a Datsun Cherry the alternator stopped working, I took the alternator apart and found the rectifier pack / diodes had exploded. So after that i always disconnected alternator also. On my Ford Escort I disconnected the battery and alternator but the Mig welding seemed to destroy the radio/cd player, it would turn on but just crackle from one of the four speakers, no other sound. Everytime I have used mig welder since then I have worried about what might get damaged particularly as more modern cars have more complex electrical stuff. So I don't know if the welding could damage it.
I would expect there to be fault codes, not sure what type of scanners you used. If you use Forscan software with a decent quality modified ELM327 code reader with the modified Ford Switch on it (eg from Tunnelrat electronics) I would have thought you'd get some codes.
Forscan is for Fords and Mazdas. It definitely works on Mazda2 DE as I have tried it.
Could MIG welding damage it? - years ago I always disconnected both battery terminals. After welding a Datsun Cherry the alternator stopped working, I took the alternator apart and found the rectifier pack / diodes had exploded. So after that i always disconnected alternator also. On my Ford Escort I disconnected the battery and alternator but the Mig welding seemed to destroy the radio/cd player, it would turn on but just crackle from one of the four speakers, no other sound. Everytime I have used mig welder since then I have worried about what might get damaged particularly as more modern cars have more complex electrical stuff. So I don't know if the welding could damage it.
I would expect there to be fault codes, not sure what type of scanners you used. If you use Forscan software with a decent quality modified ELM327 code reader with the modified Ford Switch on it (eg from Tunnelrat electronics) I would have thought you'd get some codes.
Forscan is for Fords and Mazdas. It definitely works on Mazda2 DE as I have tried it.
#3
11-20-2022, 03:47 PM
Hi isetta
First and foremost, thank you for your reply. It's so dead in here :/
Yeah, you may be right that the ABS Control Module is just plain dead, is just that it worked perfectly fine before we put my car on the lift, and then when we fixed everything suddenly there was simply no communication with the ABS Control Module (Error code U0121), so yeah, we do get a code. We used 5 different scanners - even one that is made for Ford and it couldn't find any error codes, it's only when I pull the fuze for the ABS that the check engine light comes on and gives me the U0121 error code, as explained. To the welding part: yeah it's not an old Toyota from the 80's but also not a brand new Tesla so it does indeed have some "modern" electronics in it but it's hard for me to believe that my stepdad, who's a car mechanic with 40 years of welding experience would fry my ABS Control Module with welding, then he should've also fried other sensitive components in the car and not only the ABS Module alone, in my opinion. Thank you for your input, it helps me out a lot, and it gives me food for thought.
First and foremost, thank you for your reply. It's so dead in here :/
Yeah, you may be right that the ABS Control Module is just plain dead, is just that it worked perfectly fine before we put my car on the lift, and then when we fixed everything suddenly there was simply no communication with the ABS Control Module (Error code U0121), so yeah, we do get a code. We used 5 different scanners - even one that is made for Ford and it couldn't find any error codes, it's only when I pull the fuze for the ABS that the check engine light comes on and gives me the U0121 error code, as explained. To the welding part: yeah it's not an old Toyota from the 80's but also not a brand new Tesla so it does indeed have some "modern" electronics in it but it's hard for me to believe that my stepdad, who's a car mechanic with 40 years of welding experience would fry my ABS Control Module with welding, then he should've also fried other sensitive components in the car and not only the ABS Module alone, in my opinion. Thank you for your input, it helps me out a lot, and it gives me food for thought.
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