Weird ABS issue

jsilva

jsilva

Greenie N00B Member
Greenie Member
Adding to my list of issues (I’m thinking they’re related)…

For a while ABS was activating occasionally when I was slowed down from a stop, like 5mph or less. It’s continued to get increasingly frequent and intense, and yesterday it even came on when I was driving at 35mph with my foot on the accelerator(!).

I had been assuming a speed sensor failed so I used my scan tool (ODB Fusion with enhanced Mazda diagnostics) and could see the speed from all 4 wheel sensors. So I’m pretty sure they’re not failing.

Any idea what could be going on?
 
Bad connection or faulty wiring. Inspect the wiring to each sensor
 
Easter Bunny said:
Bad connection or faulty wiring. Inspect the wiring to each sensor
Click to expand...

I’m actually having other electrical issues too. But the ABS issue happened months earlier so I didn’t see it as related.

Also, for a while I’ve been getting a CEL for low voltage if I do WOT in 2nd or 3rd gear for more than 4 seconds. I monitored the voltage and it drops at higher RPMs. I’ve seen it as low as 6V. But the alternator is producing around 14V for regular driving and the battery voltage is around 13.5V. It only drops if I’m accelerating heavily.

I will be installing a new belt and tensioner and possibly another alternator. Maybe that’s the source of all of this…
 
Easter Bunny said:
Have your battery tested too. Low voltage or a weak battery makes these cars act screwy
Click to expand...

Battery tested good at Advance Auto. I got a used alternator and tensioner and a new belt from someone off eBay. I’m aiming to install those on Tues. Hopefully that’ll at least fix the high RPM voltage drop, and maybe my other issues as well.

Yet another issue I noticed with my car is that water pools up in the rear driver’s side door. Maybe some wiring got messed up…
 
I replaced the alternator and belt tensioner today (what a pain…!). I also quickly disconnected one wheel speed sensor before I put the wheel back on just because I was sick of the ABS coming on.

Anyway, all of my other electrical issues are fixed now. So, either the alternator fixed them or maybe there is some short with the ABS system causing the other electrical issues? Maybe the alternator fixed the ABS issue too, I don’t know. Eventually I’ll reconnect the speed sensor and see.

But it was a wonderful feeling braking and not having the ABS come on :)
 
Pondering this further, it seems to make more sense that the ABS issue (a short?) caused the other issues, but I’m not sure if that is actually feasible.

Anyway, my voltage no longer drops at higher RPMs. Maybe this is my imagination, but the car feels faster. My tires squeal a bit now, even in second. I’ve had the traction control off before and I’ve never been able to squeal the tires.
 
The abs was not causing your other issues
 
Easter Bunny said:
The abs was not causing your other issues
Click to expand...

I am no electronics expert by any means. I am simply having trouble seeing how a weak alternator can affect the operation of something like the door lights coming on/off without the key in the ignition, and with the battery testing good.

The only other thing I did was disconnect the wheel speed sensor so I thought it could be related to that.

Not saying it makes sense, just explaining my thought process :)
 
i dont know how to explain it but if any part of the electrical system is weak or not functioning property it can create an output that is weaker than the car is designed for. its not like a 1970s truck, all the computers in the car are designed to work with certain voltages and a constant supply of electricity, if that isnt provided its going to screw with everything in unpredictable ways

its been documented that a dying battery in these cars will cause the idle to surge when decelerating clutch out and out of gear, no logical reason for it but it still happens.

why would you think unplugging a sensor on a completely different circuit would affect the door lights?
 
Thanks. I believe you. None of it makes sense to me :)

I wonder if the ABS issue was caused by the same thing, and maybe I didn’t even need to unplug the sensor… But it’s been fun to drive. Simply turning off DSC feels different from this. Could it be that the alternator was affecting performance and now it’s driving correctly? If so, maybe I should get my tune updated.

I’ll try and plug the sensor back in tomorrow.
 
Everything in the car is connected via CANBUS. CANBUS passes information using between 1.5 & 3.5 volts. Once you have voltage drops and spikes happening in the network, information gets crossed, backed up and read upside down etc. This leads to all kinds of stupidity...In layman's.
 
Tonight the ABS came on. I thought it was disabled? The ABS light, traction light, and DSC lights are all on.

It hasn’t come on since I disconnected the front passenger wheel speed sensor, as where previously it’d come on most of the time. I disconnected that sensor because that’s the one that sounds like it becomes active.

Does this make sense? Does it give any clues as to what the problem is?
 
i actually would have thought everything would light up when you disconnected the sensor
 
Easter Bunny said:
i actually would have thought everything would light up when you disconnected the sensor
Click to expand...

Yes the 3 lights are on.

When I said it hadn’t come on I meant I haven’t felt the ABS activate since disconnecting the sensor. Except last night when I felt the ABS come on even though all of those lights are on. I assumed ABS was off.
 
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