What the light should do
The light comes on briefly at ignition as a bulb test. Beyond that it only indicates a fault. It should not light up when the ABS is working normally under hard braking (one owner's answer, agreed by another).
It is a common fault, and usually a wire
Several owners in separate threads gave the same answer: the cause is usually a broken or worn wire going to one of the wheel hubs. Two said it normally breaks next to the hub, within about 6 to 8 inches of the sensor, so a visual check of the cables behind each wheel will often find it. Once it is fixed, a drive clears the light. Another owner found the break was at the connector, and another that the wires had snapped off at the hub itself, leaving small stubs, and the hub had to be replaced even though it was mechanically fine.
For how to find the broken wire, test it and repair it, see repairing a damaged ABS sensor cable.
Use the speedometer to rule out a wheel
The nearside rear sensor also supplies the speed reading for the speedometer. So:
- Speedometer stops, drops to zero or reads wrongly along with the ABS light: the fault is at the nearside rear wheel.
- Speedometer fine: it is not the nearside rear, which leaves the other three wheels to check.
An intermittent speedometer can come and go with the fault. One owner's speedometer worked again after cleaning and re-seating the connector at the hub, but the ABS light stayed on, so don't take a working speedometer as proof of a fix.
Checks, in order
- Note whether the speedometer is affected, and when the light comes on (always, or only on full lock or over bumps). That points to a wheel.
- Look at the wiring and connector at each wheel, with the wheel off if needed. Pull gently on the cable. The insulation can look fine while the core is broken.
- Clean the hub connector with contact cleaner and re-seat it. Also look at the sensor itself: one owner's light was caused by a dirty sensor and went away after cleaning. That is a single report.
- Test each sensor from the ABS plug with a multimeter. The pin numbers and readings are in the cable repair guide.
- Check the wiring from the ABS unit on the driver's side of the engine bay, its plug and the loom near it. One owner reported that both of his sides had wires corroded internally, giving a poor connection although the wire looked fine.
- If everything at the wheels is good, check the connections in the fuse box. One owner found a faulty connection into the base of the fuse box was the cause, after repairing a damaged sensor connector had not cleared the light.
After any fix, drive the car. Owners report the light clearing on a run after the wires are reconnected, rather than immediately. If it stays on after a drive, the fault is still there.
Reading the ABS with OP-COM
- The ABS is read from the chassis diagnostics, not the engine diagnostics. If OP-COM reads the engine but gives nothing for the ABS, you are probably in the wrong menu.
- One owner says it will tell you which sensor has failed (or more likely the wiring to it), provided the lead is wired properly.
- The same owner believes the ABS controller doesn't keep faults that have since cleared. So if the light is currently off, there may be nothing for OP-COM to report. This is one owner's understanding, not confirmed. To catch an intermittent fault, scan while the light is on.
- A fault code can clear itself once the wiring is repaired, with no need to reset it with OP-COM.
Other things owners raised
- Wheels and coding. One owner's light started after changing wheels and tyres, which led to the question of whether wheel size affects the 4-channel ABS. It was said to be coded for 17-inch wheels and had worked fine with other wheels before, and no cause was found in the wheel change itself. Whether wheel size matters is not settled.
- A coding or reset by a dealer was suggested for a car with a 4-channel ABS, but nothing in the threads shows it was needed.
If you don't want the ABS
Opinions on the standard ABS are mixed. Some owners say it is poor and have it switched off; others say it works fine, and one said it probably helped in a hard stop on a motorway. A few said it can catch you out on uneven surfaces, such as rumble strips. Test it somewhere safe before deciding. If you do want it switchable, see fitting an ABS cut-off switch. Owners planned to reconnect it for the MOT.