Leeroy_25

Okay.. I have search a bit and checked a few things and not found the answer yet. The ABS light on my FD is permanently on. key on and it's there and does not go out. I have Microtech ECU with 20B conversion if that should cause any issues due to ECU wiring? I have no idea if it was like that before as I bought the car as a non runner. is there a way to read a fault code? I assume not without the standard ECU? What and where should I start checking please to try and route out this issue. I have MOT in two weeks and this would be a fail! This leaves me very little free time to diagnose and sort the issue!

Thank you
Lee

FD3S2005

iTrader: (11)

I believe if had this issue before after jumping the car once and must of fried the way or what ever it is (I forgot) but it's a pita to take off and put on. It's above the gas pedal almost behind the center dash. I found it in the factory service manuel. But I does something with the abs. My light stayed on and I know it wasn't the unit in the engine bay. This happened like 4 years ago so my memory is a little fuzzy. If I was home and not on my phone at work I would be able to help a bit more

Leeroy_25

thanks for the reply.. if you can give me some more details when you get home that would be much appreciated. I think this is going to be one of the head aches you don't need kind of problems!

Cheers
Lee

billyboy

Last time, simply cleaning the sensors of magnetic debris put out the light.

You don't say what year your car is? If it's not an early one, a scan tool or a led with resistor between gnd and tbs in the diagnostic box will generate codes in a rhd.....it should be ok unless the Microtech has been hacked into the abs computer wiring, wouldn't put it past some installers, at least here!

Leeroy_25

My car is a 1994. I did the ECU install and have not butchered any of the wiring or cut anything intentionally that was not needed for the ECU? I presume there are relays and fuses in the cab and engine bay. Would these cause this issue? as in should I check any of this first?
I have a feeling this is going to be a right headache! I will check sensors for debris too.

Thanks for any help.

Lee

DaleClark

iTrader: (55)

Search around on this. There is a way to check codes for the ABS system.

Dale

billyboy

If it's post 7/94, it should be like this in the diagnostic box -



the earlier "fat" ecus from 91 and mid 93, didn't have the terminals to bridge. I seem to remember there's a light on the computer, but never had need to look at a malfunctioning one.

cewrx7r1

iTrader: (2)

I has an ABS light a few years ago. It was inconsistent. First I check the supply +12V voltages for the controller in the trunk/boot and at the solenoid unit on the firewall. All was good. Next I check the outputs for all four wheel pickups and all was good.

I even installed a new diode in the solenoid unit. No fix.
Then while checking the +12v at the solenoid unit, I move the wires for the connectors and the voltage fluctuated.

Taking the connectors off and inspecting them revealed the problem.
One of the +12v leads in a connector was almost burnt out.
I replace both the male and female pins and that fixed the problem.

Now these connectors where never disconnected by me until this problem occurred.
Evidently the problem was due to Mazda's wiring supplier. The male and female pins where not making a tight enough contact. This caused a point of higher resistance which caused local heating. This caused pitting/burning of the metal and after many years it failed.

We all hate Mazda wiring!

gracer7-rx7

iTrader: (16)

Does the ABS work? Have you tried standing on the brakes and see if it pulses or whether you have a wheel that locks up?
That is the first thing I'd do as it will help point to a particular wheel or front/rear where an ABS sensor might have failed. The wires in the front sensors often get stretched and broken b/c people don't remove them from the hubs when installing/removing shocks.

Check is the resistance on each ABS sensors. The FSM has the procedure and specs. It's quite easy.

Leeroy_25

I made a start looking at this over the weekend.. I have pulled off all the plugs on the four sensors and checked resistance. These all appear in spec. Plugs look fine too.
I also dusted off the ends of the sensors at the hub end and that seems fine too. No major build up anyway. Light has remained on.
So next step? Am I going for checking continuity somewhere or voltage to something?

I just looked at my Diagnostic box and I think that is the same as that. but does that only work with the stock ECU? I have a microtech fitted. I will pull the plugs off at the solenoid end and check that if I can next. How do you get the lid of the electronics box to check inside there looks okay? it seems like the middle pipe on the system prevents you getting the lid off?!

Thank you
Lee

Leeroy_25

Can someone please confirm what to check next and also if diagnostic only works with stock ECU or if it will still work with my mircotech.

Thank you
Lee

rexset

I have similar problem some time ago , it was one of the pins of the connector of the valves motor (or ABS motor), very hard to find thou
I fix it in a very peculiar way cause the connector was broken , but it never fail again.

billyboy

Just to confirm you have a blue label (probably faded) F123 prefix abs pump?

The microtech shouldn't effect the abs diagnostics.

Here's the list of "light on" causes -



fault codes -







If you end up truly confused, dealers should still have their equipment to diagnose, but any half-equipped sparky probably can help.

ArmenMAxx

iTrader: (21)

Make sure the fuse for the rear wiper is good (drivers side fuse box under the dash). I pulled it on my R1 since it has no wiper, and my abs light turned on with no abs.

Leeroy_25

Finally got around to looking at this! I tried the diagnostic box and either where I am running a Microtech ECU this no longer works or The fault is just solid light. As the light was on and stayed on following the diagnostic procedure posted. This being the case what and how do I check first.

Thank you
Lee

Leeroy_25

Update.. Had a a closer look at my diagnosis box. It does not have the terminal there to bridge for abs?! No wonder it didn't work. Started a new thread with more info now.