I have the ABS light coming on intermittently. Some days it’s on when I start the car and stays on. Then the next day it’s off and stays off. Occasionally it comes on mid-journey. I have looked at the method for reading the fault codes in the FAQs and I’ll be doing that next time I get a free day. My question: does the ABS light need to be on when I read the codes? In other words, do I need to wait for a day when the light is illuminated, or will it show the fault code even if the light is off that particular day?
IIRC the fault code is stored in memory so will read even if light is not on at the time.
Be prepared for a front wheel sensor change though, as this is usually the first sign of one going.
As a 99 it won’t have an OBD2 port so you will need to use the under bonnet one. It is quite easy to do and all you will need for an ABS check is a paper clip. It is probably going to be one long and either one or two short flashes of the abs light on the dash (11 or 12 left or right sensor)
You can also check by using a meter on the connector under the bonnet to see if it is reading aa resistance or open circuit (broken!)
If it does read out as a sensor shout as there is a how too on changing one. Also don’t rush out to purchase an OEM one without checking posts on here as there are some much cheaper alternatives on the well known auction site.
Thank you for that. I am assuming it is a dodgy sensor, and I have read the posts on that. I’m prepared for a fight getting the old one out.
Not sure about sourcing a new one. Some posters are saying that the cheaper eBay ones don’t last very long. I suppose, if I have to change it again in a year or two it will at least be an easy job, as I will already have dealt with any long-term corrosion the first time.
Hi, I had exactly the same symptoms on my 10th Anniversary (1999) 2 years ago. After all the usual checks, resistance tests, etc. I got a new sensor by ordering it at the National Rally (thus 10% off). After all the “umming and aahing” I decided it was best just to get an oem part and be done with it. No problems since (touching wood!).
Good luck.
Right, finally I have got round to it. Too many old cars, not enough time! I did the GRD/TBS bridge and got the fault codes - 11, 41 and 42.
11 - Right Front Wheel Speed Sensor Open circuit or Short to power supply 41 - Right Front Wheel Speed Sensor Rotor Short to ground or Disagreement with other sensors is detected 42 - Left Front Wheel Speed Sensor Rotor Short to ground or Disagreement with other sensors is detected
I’m assuming the 11 and 41 relate to a goosed RHS front wheel sensor, and I’m hoping that the 42 is the LHS sensor complaining that it can’t agree with the RHS sensor. Would that be a reasonable assumption? Time to start looking for a new RHS sensor.
When the codes had run through 2-3 times, I tried hitting the brake pedal 10 times in quick succession to clear the codes, but this didn’t work. The codes still show if I switch the ignition on with the bridge in place. What am I doing wrong?
Thanks for all the help so far.
Edit: the RHS sensor showed a reading of 6-7 mega ohms, so I guess that is virtually a short. I tried to check the LHS for comparison, but couldn’t get the bloody connector off!
The sensor coil resistance should be between 1.4K Ohms and 1.8K Ohms.
With a multimeter on it and slowly spinning the wheel (about one rev a second) expect to see something between 0.25V AC and 1.2V AC. An oscilloscope will show a squarish waveform with transition spikes corresponding to the edges of the rotor going past the sensor. Too much speed and the signal gets bigger into a high impedance, but normally it is terminated correctly at the control module to keep it in check.
RichardFX, thanks for the information. I’ll check that out when I get it on the jack.
I have found a genuine sensor from MX-5 Parts for £178, or one on eBay for £24. I’d go for the cheaper one, but the guy needs a part number as there are two versions for the NB. Any idea where I can find an online parts catalogue with the original part numbers?
No luck getting a part number, so rather than risk buying the wrong one I bit the bullet and got a genuine sensor from MX-5Parts. The good news is that I have fitted the sensor temporarily and the ABS light goes out, so I have correctly located the problem (o/s/f sensor). Now waiting for suitable weather and a day off work to get it fitted.
Just to update the thread. All sorted. The sensor wiring bracket bolts all come out without a fight, although the thin metal bracket at the rear of the hub broke off. There was enough left to drill a new hole, so that got the rust treatment before I continued. The sensor bolt sheared off and I totally failed to get the sensor out of its housing in the hub. I ran out of time and patience, so I took it to my local independent. I fitted the new sensor with all the brackets and left the sensor cable-tied to the upper arm, so all he had to do was remove the old one and bolt in the new one. Two days later … Apparently it was a struggle, so I am glad I gave it up when I did. He rebuilt the caliper with the other half of the kit I supplied, so now the car has a functioning ABS system, and fresh pistons and seals both sides at the front. It now stops well and the front brakes are running cool again. Job jobbed. MoT next month, so hopefully all is well. Thanks to all for the help and advice.