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Abs light always on

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Airwolf

Member
Joined
Apr 7, 2022
Messages
58
this is the final issue I’ve got to solve to make this car as new

Basically - when I turn the ignition the 4w abs light is always lit up and never goes out

What’s the best course of identifying the issue? I’ve got a new ecu coming in case the one I have is not compatible as this car is a bit of a mix and match job as it was just a shell when I got it

Thanks !
 
At a guess I'd say your ABS computer or one of the sensors is broken.

Most people just remove the ABS and the bulb.
 
I had that and it just turned out to be a dirty wheel speed sensor.

If you get a slightly more expensive multimeter you can test the abs sensors.
 
I have 2 rear abs sensors for sale in good condition if you want them or just take the ABS bulb out lol
 
Seems to be the front driver side sensor is causing the issue as the ohms reading is spiking all over the place - will double check as it’s hard to hold the probes onto the clips. Is this a likely symptom of just a cause of me not being able to hold the probes correctly

Not checked the back yet as they are hard to get to

Anyway to check the abs pump ?
 
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Reading JDM stock ECU fault codes

Might be useful for standard FD users Nice to have all the info in one place, courtesy of wstrhom on rx7club.com or this thread here: http://www.rx7club.com/3rd-generation-specific-1993-2002-16/how-read-fd-trouble-codes-851414/ Copied below for convenience...
fdoc.co.uk fdoc.co.uk

I wrote (and did) this a few years ago, and it worked for me. I'm in Bridgend too, but my cars been mostly off the road in all the time since then o_O
 
Has anyone tried the mx5 na abs sensors ?

The front abs sensors for the fd are discontinued and a whole mx5 set can be had for 160. Can’t find the specs of the sensors online though
 
So found a thread on another forum and it seems the mx5 nb are a match

I have some good news. I took a chance on the Mazda Miata (MX-5) MK2 ABS sensors. I replaced both fronts for less than £60. The dash light went off straight away. I've been driving her for a few days now, and it hasn't come back on. Success.

A few things to note:

1. I have an Apexi ECU (I don't know if it changes how the ABS behaves).
2. The hole in the knuckle for the sensor measured 18mm in diameter, but there were a couple of high spots from the casting process. I took an 18mm drill and knocked those high spots off.
3. The wire does point in the other direction, but with enough slack, it doesn't rub at full lock. All other vital dimensions match up.
4. The connectors do not match, and it's not just a case of de-pinning and swapping them over. I elected to upgrade to Deutsch connectors.
Click to expand...

ABS Sensors Alternatives? - RX7Club.com - Mazda RX7 Forum

New Member RX-7 Technical - ABS Sensors Alternatives? - Hi All, The front right ABS sensor on my FD has stopped working (no continuity). After having a minor heart attack, when I saw the price of a replacement, it got me thinking. Does the ABS system care what resistance/voltage it reads so long...
www.rx7club.com

So I’m going to pick up a whole new set and report back - one thing though the guy in the thread used the mx5 nb set - I think the na set would be a more direct swap so will try them out first - not sure on the rears though as their mounting points seem different
 
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Airwolf said:
So found a thread on another forum and it seems the mx5 nb are a match



ABS Sensors Alternatives? - RX7Club.com - Mazda RX7 Forum

New Member RX-7 Technical - ABS Sensors Alternatives? - Hi All, The front right ABS sensor on my FD has stopped working (no continuity). After having a minor heart attack, when I saw the price of a replacement, it got me thinking. Does the ABS system care what resistance/voltage it reads so long...
www.rx7club.com

So I’m going to pick up a whole new set and report back - one thing though the guy in the thread used the mx5 nb set - I think the na set would be a more direct swap so will try them out first - not sure on the rears though as their mounting points seem different
Click to expand...
I guess it depends if the tooth ring is the same size and step count. If it is, then that's half the battle.

Is your existing sensor not repairable? i.e solder it?
 
Sensor is the actual item that has failed over it’s cabling sadly

As an update - it is the na or very early nb sensors that’s required for the front. The rears don’t fit as the sensor pin bit is too far out although if a gasket could be made up it will work too
 
Ok back to square one - sensors are good but still abs light

Not able to use the diagnostic box as I don’t have a Tbs connector

How best is it to test the abs pump / unit

IMG_7756.jpeg
 
Ok so reseated the front sensor and cleaned the connectors of the abs pump and we have success - no more abs light

The mx5 sensor works though ! - just need to swap over the connector and cost 30 quid

IMG_7771.jpeg
 
Thread revival 😁 So my issue is that when I turn the ignition on and start the car the ABS light does not come on. It does come on as soon as the car start moving. I replaced the front passenger side sensor after I broke it replacing the suspension. The light came on after I replaced it with a second hand sensor. So not sure if I need to reset the ABS ECU or did I buy a dodgy sensor?
 
Test your sensors resistance with a multimeter, normal will hold constant resistance in the specified range, if failed the resistance will fall as you read it, or just be completely out of spec.
 
Airwolf said:
Ok so reseated the front sensor and cleaned the connectors of the abs pump and we have success - no more abs light

The mx5 sensor works though ! - just need to swap over the connector and cost 30 quid

View attachment 39647
Click to expand...
Slight revival (and a very long time since I last posted anything here), I've had to replace my front passenger wheel sensor, but not had the same success with the NA MX5 sensors.

Did you replace both front sensors or just the one that was broken? And do you know what resistance the MX5 sensor measured? The ones I have read 1600ohms which is a little higher than the RX7s ideal range (800-1200).
 

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