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Discussion Starter · #1 ·
Thanks for checking out the post.
From what I’ve gathered a bad sensor could be causing all of my problems just not sure which one.
So I have an ABS,TCS,TPS,Brake,and power steering lights all on. The speedometer also is not working. I have replaced both front wheel speed sensors. OBD2 says speed sensor A I do not have a way to pull ABS codes. No auto parts sorted near me have this capability also. Instead of just throwing sensors at the car I’m up for suggestions. I have electronics experience so I’m handy with a multi meter and schematics so if anyone can help out with schematics that would also be helpful.
Thanks for your time and assistance!
 

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What's the exact OBD-II code displayed? P0500? I think you'll need to dig into whether there are ABS or DSC codes, as the service manual directs resolution of that rule-out before the last resort of replacing the PCM.
 

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2018 Mazda 3 GT
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How's the battery? Have you tried disconnecting the negative terminal for it and reconnecting it after 15 mins to reset the ECU? You can also pump the brakes 5 times after disconnecting it if you don't want to wait.
CK
 

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Discussion Starter · #4 ·
How's the battery? Have you tried disconnecting the negative terminal for it and reconnecting it after 15 mins to reset the ECU? You can also pump the brakes 5 times after disconnecting it if you don't want to wait.
CK
Thank you for your post,
I have tried resetting the codes via the method you referred to.
 

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Discussion Starter · #5 ·
What's the exact OBD-II code displayed? P0500? I think you'll need to dig into whether there are ABS or DSC codes, as the service manual directs resolution of that rule-out before the last resort of replacing the PCM.
P0500, speed sensor A, I have no way of checking the abs light I went and bought another scan tool and it sid my car was not supported for live data or abs. Would you happen to know where the vehicle speed sensor is located on this vehicle I have been up and down the transmission with no luck and I’m not finding anything online for the location. This will be the next sensor I throw at it after that it may need to go to a shop for diagnosing the abs system
 

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P0500, speed sensor A, I have no way of checking the abs light I went and bought another scan tool and it sid my car was not supported for live data or abs. Would you happen to know where the vehicle speed sensor is located on this vehicle I have been up and down the transmission with no luck and I’m not finding anything online for the location. This will be the next sensor I throw at it after that it may need to go to a shop for diagnosing the abs system
Looking at the service manuals for the car and the transmission (G35M-R), I don't believe the MTX with ABS uses a discrete Vehicle Speed Sensor -- it uses the ABS wheel speed sensors instead.
Rectangle Slope Font Schematic Parallel

It may go without saying, but are all your ABS fuses (see above diagram) verified as good?
 

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Discussion Starter · #7 ·
Got it fixed

ABS reader pulled both front ABS sensors were faulty. Turns out I just replaced the wheel speed/ ABS sensors in the front. With no information from either front wheel to the ABS module and the to the ECM the car did not know what wheel was spinning and at what speed this took out the speedometer, ABS light on, check engine light on, TPS light on and brake light on (the one that comes on with the parking brake). And it had no power steering. So after pulling the front passenger side wheel bearing it was noticed that it was replaced by the previous owner with out the ABS required wheel bearing (coil plans or magnet in this bearing sends data to ABS/ wheel speed sensor) after replacing that with the e correct part I went to the drivers side it had the correct bearing but had failed internally some how after replacing them myself there are no more problems with the car except a random MAF sensor code but that come and goes and will most likely be a wire since it is a new sensor I just wanted to share my findings and information and thank all of those that helped me find the solution.
 

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I have been having very similar problems and since I bought the car from day one the ABS light has been on and I thought nothing of it. Until the problems began, and they sound eerily similar to what you went through. I never thought about getting the abs codes pulled but I will now that I've read this post. You may have indirectly helped fix this nightmare of issues I've been having and for that I thank you.
 
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