- My model of MX-5 is: __2013 Mk3 Sports Graphite
Based in Hampshire
- I’m looking for technical help or recommendations on: __
I’m getting my ABS, TCS lights illuminating whilst driving and also my cruise control won’t engage.
This was at first very intermittent, but now on most drives they come on. Not always immediately , but after a few minutes/miles!
I’ve tried removing and refitting a couple of fuses, to no avail. Also removing and refitting the ABS unit plug.
I’m thinking maybe a dodgy connection somewhere! Any ideas ?
I’ve read the ÉCU is in the pax footwell.…. Suspect???
Everything else appears normal on the car
Help 
My initial thoughts would be a failing or poor connection on a wheel speed sensor. There are 4, one for each wheel and it only takes one to bring the warning lights on. I would suggest that you arrange for a code reader to be plugged into the diagnostic port and read any codes to help identify which component is playing up.
Your engine ecu is below the battery in the engine bay.
Thanks for that… I did try to find the écu under the battery, but it wasn’t very apparent, hence I thought it might be inside. …
I did get it serviced recently, but because the fault wasn’t there, the garage wasn’t able to help!
I’ll try again when the fault is live.
Thanks again
ECU under the air intake/filter box.
Hmm, amongst other things that can also be a symptom of water ingress though the notorious passenger-side grommet! In this case expect damp carpet and rust streaks on the bare metal behind the glovebox.
Also look for any stored fault codes with an OBDII reader.
Then it could be low battery voltage, and I suggest you check the terminals are secure and that it is charging properly.
I also had a similar show of lights when I forgot to plug in the climate control unit after taking the head-unit out. But if nothing has been disturbed then this sort of thing is highly unlikely.
Yes good call on the battery by Richard, check if it’s not going bad, the connections clean/secure and of course the water getting in etc.
I had a battery on a non Mazda go weak, it started the car fine, everything worked ok until it threw up traction control lights and an engine light and went into limp mode. New battery sorted it.
Process of elimination before you start on the ECU.
Mine isn’t going into limp mode.
But I did notice the lights, if on when starting, don’t go out until about 15 mph.
( I thought all lights should go out after initial start up check?) … I might be wrong and thinking about it too much . Lol
And then come on again when the fault comes back .
I’m booked into the garage next week, but at £130 per hour.!!
I thought I’d try and do some trouble shooting.
Thanks for your ideas…
But Would a dodgy wheel sensor prevent me from engaging cruise control?
Another possibility comes to mind, but it depends on what Tyre Pressure Monitoring System you have.
It might be using the ABS sensors (and then have rubber valve stems), or like my 2014 NC3.75 the wheels might have TPMS valves with metal stems, as in my pic.
Now the crucial point, hypothetical, but a possibility depending on how the ABS etc software has been set up.
If the valves are the sensors, the battery life in them is about ten years (mine were still working at ten). Your car is eleven years old and bound to have had the tyres changed by now, BUT if originally fitted, were the TPMS valves also renewed, often at about £60 each wheel?
If one or more valve sensors are barely working, or dead, then there could be a logical conflict with info derived from the ABS sensors, hence confused lights on the dash.
A hand-held reader exists which can interrogate each wheel to find out about the status of the TPMS valve. It’s a faff to use but I’ve recently seen one working.
And one other possibility, are all the tyres the same make and type and size and age?
I ’ve had it since 2016, and I’m not aware of any TPMS fitted.
I’ve cleaned the battery terminals, and nipped up tight
I’ve just had a look at the ECU.
I was hoping to cycle the plugs in and out, but it appears to have anti tamper proof nuts on the housing so have left alone.
All back together bar a test drive…. But not expecting miracles.
So…. Test run still showing intermittent fault .
I’ve borrowed an OBD tester and looked for faults, but no joy.
But then, the fault wasn’t there when I stopped .
The unit is also saying it’s got a link error!
Think I’ll plug in the tester when the fault is showing, and see if anything shows, or any link problems?
Some OBD testers don’t show all codes, it may only show engine faults.
If you can get hold of an elm327 adaptor and download Forscan for free on to a laptop.
Forscan will give you much more detailed data.
An update for those interested… car went into the garage for a rear abs sensor change last week …
no problems or msgs since 
… 
Thanks all for comments .
