Kia Picanto ABS

[Richyvrlimited]

My sister's car is exhibiting behaviour I've not experienced before, the ABS is engaging even on light brake applications.

I've given the brakes a once over, and other than the offside rear handbrake being a bit poor, the brakes generally are fine.

I re-bled the brakes and found quite a bit of air in the system, I think I've got all that out now, but as worried some is trapped in the ABS pump which I've heard can be a bugger to sort out. (pressure bleeder?)

After bleeding whilst the pedal feel was better the ABS issue was still occuring.

What could be the cause? The ABS light is unlit - I've checked the bulb - so I'd written off a failed sensor, but could it have failed in an odd way to cause this issue? If so how would i trace the broken sensor?

[DuraAce]

Fault code scan might help, you could also measure the resistance of each sensor, a dodgy one will have a different reading to the others.

Are all the castellated reluctor discs on each hub secure? Sometime they can be rusted and loose etc. This could cause the abs to trigger.

[Richyvrlimited]

DuraAce said:

Fault code scan might help, you could also measure the resistance of each sensor, a dodgy one will have a different reading to the others.

Are all the castellated reluctor discs on each hub secure? Sometime they can be rusted and loose etc. This could cause the abs to trigger.

I'll check the trigger wheels are all secure this weekend.

Surely is the resistances of the sensors were different the ABS system would throw a code?

[was8v]

Richyvrlimited said:

Surely is the resistances of the sensors were different the ABS system would throw a code?

Have you done a code scan? not all faults will throw the light.

I had a VW once that had loose ABS "cage" / ring on the back of a rear disc with the symptoms you describe.

[Penelope Stopit]

Hi. The first thing to do before getting deeper and deeper involved is to put a fault on the ABS to be sure the ABS light is working correctly
Disconnect one of the four wheel sensors and drive the vehicle for a short distance, the ABS light should illuminate
If the ABS light is working correctly after doing the above there is a very good chance that the sensors or ABS hub rings are dirty or corroded
Dirty or corroded sensors or rings will give a signal to the ECU that makes it think that one or more wheels are moving slower than the others and the ABS will kick in

Post back with your findings

[Mr2Mike]

Richyvrlimited said:

My sister's car is exhibiting behaviour I've not experienced before, the ABS is engaging even on light brake applications.

Does it only activate at low speeds, e.g. when pulling up to a junction? If so that is a classic symptom of either a broken reluctor ring or a partly dead sensor.