ABS and brake warning lights on

Good morning , I would llke a bit of advice please , I have a 2002 citroen c3 petrol , I have an issue with the Asb light ,I have checked the fuses , I have cleaned the rear magnetic rings , no difference , the next thing to check is the front/rear sensors.
I appreciate there are lots of posts here re the same , however I would like to clarify something.

Does the fact that the Asb light AND the brake light illuminate point to anything more obvious that just the Asb light being on.

Also does the fact that sometimes both lights come on on start up and sometimes it takes ½ a mile for them to come on mean anything? , from previous posts it does seem that the start up process should detect a faulty sensor , however it sometimes does and sometimes it takes a short journey , however it does eventually illuminate on every journey,
I haven’t got a code reader so my intention is to buy a new sensor and use a multimeter to check sensors on front to see if it helps and if not to swap it to the otherside.
Can someone please confirm what sensor readings should be , Thanks.


Thanks in advance,

Hi

Connect lexia and it will tell you which wheel sensor is at fault and concentrate your efforts on the one, rather than on the ones that is isn't.

This can save a lot of time, particularly if it turns out that the fault that brings up the ABS warning is not a wheel sensor, but some other ABS fault.

If you are just checking resistances, and suspect one faulty sensor, would you get 3 similar reading and one different?

Trouble is the fault may be intermittent and resistances won't help, but stored fault logs will.

The sensors are just a coil of wire so you would expect the resistance to be only a few ohms. However corrosion on the reluctor ring (in the bearing) or metal filings on the end of the sensor will stop it from working correctly.

The "brake light" is only used for the hand brake and master cylinder fluid pressure/level. I.E. your low on brake fluid. Checked the fluid level?
Have you removed the bag from the ABS module connector, removed the connector and checked for corrosion on the plug and socket?

As the guys have said, without an error code we are just guessing.