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2020 CX-30 GT Tech Auto
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Discussion Starter · #1 ·
Nearly ran over a pedestrian as foot brake pedal went solid & would not depress when moving, frightening.. Anybody else suffers this?
To replicate the issue start your auto CX 30 then switch off. leave 5 mins then restart. As you do so apply the foot brake & you may find that the footbrake will not move (Mazda have confirmed in writing that this can happen in not just my vehicle). This sequence replicates the effect I encountered & is what Mazda describes, in writing, as a "characteristic". This effect has been demonstrated at my local dealer but only stationary (vehicles were parked in front of my vehicle). My issued first occurred when the battery was partially discharged, car started OK, but brakes did not work whilst in motion. tried to reject car through finance company (Santendar) but they have accepted Mazda's report on the matter.
UK Governments car safety body DVSA is in talks with Mazda Japan & so far has not received enough information to disperse they concerns. Mazda do not seem to be taking this seriously but you only need to be moving slowly to pull in to the path of an oncoming vehicle? I have been in dispute with Mazda now for nearly a year.
My vehicle is due to be be returned from the dealership to me this Wednesday (2 June) which will enable me to conduct further tests, I will post more info when my vehicle is returned.
Would be very interested to hear from anyone that has experienced the same or can replicate the solid brake pedal ( I apparently damaged the braking system as I, according to the vehicles log, "applied excessive pressure" as you would when trying to stop from hitting someone), I would be extremely interested to hear from anyone that has had the same problem or tries the 5 min example & then (if safe to do so) engages drive and checks if the foot brake works.
As the CX30 is based on the 3 I suspect this will exhibit the same issue, please confirm.
Please stay safe.
At this stage no recalls have been announced for this issue.
 

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2021 CX-30 2.5L AWD Pearl White
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If you reacted after the car did you can encounter a harder brake pedal than "normal". But as you push on the pedal you can apply the brakes over and above what the car is already doing.

In order for the car to go into automatic braking it has to first close the isolation valves to the wheels, and then it runs the pump inside the ABS controller to build pressure in the brakes. By design these valves close to prevent the pump pressure from simply returning upstream to the master cylinder, but when you then hit the pedal the master cylinder pressure can force them open and apply even more braking pressure. Since the brakes are already being applied, and you have to overcome the isolation valves (which isn't hard to do) the pedal will feel hard to you.

You can get the exact same pedal feel if you try to apply the brake after the radar cruise has already started to slow the car down. The system will react and turn the isolation valves off, but the brakes are already applied so the pedal does feel high and hard.
 

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Discussion Starter · #3 ·
If you reacted after the car did you can encounter a harder brake pedal than "normal". But as you push on the pedal you can apply the brakes over and above what the car is already doing.

In order for the car to go into automatic braking it has to first close the isolation valves to the wheels, and then it runs the pump inside the ABS controller to build pressure in the brakes. By design these valves close to prevent the pump pressure from simply returning upstream to the master cylinder, but when you then hit the pedal the master cylinder pressure can force them open and apply even more braking pressure. Since the brakes are already being applied, and you have to overcome the isolation valves (which isn't hard to do) the pedal will feel hard to you.

You can get the exact same pedal feel if you try to apply the brake after the radar cruise has already started to slow the car down. The system will react and turn the isolation valves off, but the brakes are already applied so the pedal does feel high and hard.
Hi John,

Thank you for your very interesting reply.

Below is an extract of a timeline that I provided to the DVSA to set out the details of each event which covers the first instance back in July 2020. I would be keen to know whether you think your observations would apply to this event?

"27 July 20
Having reversed into a parking slot at the local supermarket, about 1 mile from work, and returned from buying lunch being in a hurry I started the car & unlike normal engaged forward drive before putting the seat belt & glasses on (with the intention of doing so as I drove down the service road).
As I partially released the pressure on the foot brake to creep forward out of the parking bay I could feel the pedal pulsating in sync with the clicking noises.
As I cleared the bay I released the pedal to accelerate down the service road and maybe a second later a pedestrian stepped out from behind a car into my path. With the clicking noises still audible I stamped on the brake pedal to perform an emergency stop but found that the pedal would not move. When the noises stop the pedal could be depressed and the car brought to a halt without hitting the pedestrian. Not sure if I released the pedal and the noises stopped or whether the noises just stopped."

The cure offered by the dealer was to charge the battery, yet the car had started ok?
Cheers Andy
 

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I noticed this from initial ownership, but adapted my driving to suit.
If I release the brake pedal fully, then re-engage the brake pedal to select a gear, all is well.

If I keep the brake pedal down, start the vehicle, engage a gear and partially release the foot brake to creep forward or back, then per your observation, the brake pedal is very hard with pulsing / clicking.

It caught me out at first, but now release the foot brake and re-apply between start and gear selection.
 

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Discussion Starter · #5 ·
I noticed this from initial ownership, but adapted my driving to suit.
If I release the brake pedal fully, then re-engage the brake pedal to select a gear, all is well.

If I keep the brake pedal down, start the vehicle, engage a gear and partially release the foot brake to creep forward or back, then per your observation, the brake pedal is very hard with pulsing / clicking.

It caught me out at first, but now release the foot brake between start and brake selection.
Hi Paul,
Many thanks for your swift reply. Would you be willing for me to share this information with the DVSA?

Cheers Andy
 

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That's enough information to start investigating the vehicle for a possible problem and that's all that it is.

The questions that need answers are first, what exactly was clicking? If it was one or more relays, which relays was it and then the question shifts to "why" were they clicking?

As far as the pedestrian scenario, again there are questions that need to be considered. Were you distracted by: The clicking sounds? The preoccupation with planning to buckle the seatbelt? Or, Something else that you just don't recall at the moment? Which leads back to my first question. Did the car react to the pedestrian faster than you did because of everything else that was on you mind?

It's easy to just assume that everything you have noted is related, but that's a trap when it comes to actually figuring out what really happened. There is no real evidence here to prove what you were observing has a singular origin.

As far as what the technician did finding the battery undercharged is easy and under some circumstances a charging system, or system power issue can produce some strange behaviors. For the technician trying to earn a living fixing cars, they have to do something to get paid anything for the time to start investigating/testing.

What I would need to know to even start working on this effectively is how likely is the symptom going to occur if I drive the vehicle on a normal test drive? How long, or how many times could I drive the car and no symptom occur?
 

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Discussion Starter · #8 ·
That's enough information to start investigating the vehicle for a possible problem and that's all that it is.

The questions that need answers are first, what exactly was clicking? If it was one or more relays, which relays was it and then the question shifts to "why" were they clicking?

As far as the pedestrian scenario, again there are questions that need to be considered. Were you distracted by: The clicking sounds? The preoccupation with planning to buckle the seatbelt? Or, Something else that you just don't recall at the moment? Which leads back to my first question. Did the car react to the pedestrian faster than you did because of everything else that was on you mind?

It's easy to just assume that everything you have noted is related, but that's a trap when it comes to actually figuring out what really happened. There is no real evidence here to prove what you were observing has a singular origin.

As far as what the technician did finding the battery undercharged is easy and under some circumstances a charging system, or system power issue can produce some strange behaviors. For the technician trying to earn a living fixing cars, they have to do something to get paid anything for the time to start investigating/testing.

What I would need to know to even start working on this effectively is how likely is the symptom going to occur if I drive the vehicle on a normal test drive? How long, or how many times could I drive the car and no symptom occur?
Please see the response from PaulF who has learnt to "drive around it" . I have had three occurrences in c.3000 miles and it does seem to be at startup after a short journey. As previously mentioned the car has always started.
 

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Please see the response from PaulF who has learnt to "drive around it" . I have had three occurrences in c.3000 miles and it does seem to be at startup after a short journey. As previously mentioned the car has always started.
Three events in 3000 miles. That would make it very difficult to duplicate. Being able to get a symptom as described by PaulF is good information but still has to be confirmed to be relevant to what you are describing. The ABS/Traction control system does have to perform self tests at every start-up but they are very fast and difficult to observe even when you are specifically trying to. "IF" someone does notice these self tests they would be normal behavior and not a problem with the car.
 

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Discussion Starter · #11 ·
Three events in 3000 miles. That would make it very difficult to duplicate. Being able to get a symptom as described by PaulF is good information but still has to be confirmed to be relevant to what you are describing. The ABS/Traction control system does have to perform self tests at every start-up but they are very fast and difficult to observe even when you are specifically trying to. "IF" someone does notice these self tests they would be normal behavior and not a problem with the car.
This only occurs in cars with an automatic gearbox?
Not driven a manual so can only confirm on an automatic. Does anyone know different?
 

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Discussion Starter · #12 ·
Three events in 3000 miles. That would make it very difficult to duplicate. Being able to get a symptom as described by PaulF is good information but still has to be confirmed to be relevant to what you are describing. The ABS/Traction control system does have to perform self tests at every start-up but they are very fast and difficult to observe even when you are specifically trying to. "IF" someone does notice these self tests they would be normal behavior and not a problem with the car.
Started the car this evening. After switching off I started a timer. At 3 minutes gone you hear a whirring noise. At 5 minutes you hear a loud click start the car at this point and put your foot on the brake pedal and it will not move down even when releasing the parking brake. What you feel is the solid pedal. This is not the problem if the battery is fully charged as as soon as you release the pedal the normal brake pressure returns. My incident occurred after a Covid lockdown related period of working from home. With a partially charged battery the brake pedal pulsed maybe 3 or 4 times as I released it and went solid on reapplying with no noticeable retardation until I pumped the pedal.
Will turn the radio on for a while and repeat the test in a few days.
 
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