2004-2006 Scion xA ABS Light On: Common Causes and Fixes

By Core Brake Parts Tech Team — Circleville, OH warehouse

When the ABS light stays on in a Scion xA, the anti-lock system has found a fault in something it monitors and has switched itself off. Your normal brakes still work, but the wheels can now lock in a hard or slippery stop. The most common causes are a wheel speed sensor or its wiring, a problem at the sensor's toothed ring, mismatched tire sizes, a blown ABS fuse, or low brake fluid, and the first step is always to read the stored trouble code.

The xA was sold for the 2004 through 2006 model years; Toyota's own recall paperwork lists production from late January 2003 to early January 2007, which is why parts listings often show "2003-2007." Everything below applies to all of them.

How the ABS System Works on the Scion xA

Every xA came with four-wheel anti-lock brakes and electronic brakeforce distribution (EBD), with front disc brakes and rear drum brakes. According to the owner's manual, the system "detects vehicle speeds using the speed sensors for respective wheels' turning speeds." A computer compares those four signals. If one wheel slows much faster than the others during a stop, the actuator pulses brake pressure to that wheel so it keeps turning and you keep steering control.

A few operating details from the manual are worth knowing because they are often mistaken for faults:

• ABS only becomes active above roughly 6 mph and stops working below roughly 3 mph.
• A click or motor sound from the engine bay for a few seconds after startup or as you pull away is the system's self-check, not a failure.
• During an ABS stop you may feel the pedal pulse, hear the pump, and feel vibration in the body and steering wheel. The pedal may move slightly forward at the end of the event.
• The ABS light should come on when the key goes to ON and go out after a few seconds. That bulb check is normal.

Some xA models were equipped with vehicle stability control (VSC) and traction control. On those cars, when the ABS light is on, the manual says ABS, brake assist, traction control and VSC are all disabled, while the base brakes still operate conventionally.

ABS Light Alone vs. ABS Light Plus the Red Brake Light

This is the most important thing to check before anything else, because the two situations are very different.

The xA's hydraulic system is split into two separate circuits. If one fails, the other still stops the car, but the pedal gets harder and stopping distance grows, and the red brake light may come on. Treat any red light seriously.

Common Causes of an ABS Light on the xA

1. Wheel speed sensor or wiring

This is the most frequent cause on any car of this age. Each wheel has a magnetic sensor that reads a toothed ring as it spins. The sensor can fail internally, its tip can get coated in metallic debris and rust, or its harness can chafe, corrode at the connector, or get torn during suspension or axle work. A code will usually name the exact wheel and whether the signal is open, shorted, or erratic.

2. Damaged or rusted sensor ring

The toothed ring the sensor reads can crack, lose teeth, or get packed with rust scale. The sensor then sends a signal that drops out once per revolution, which the computer flags as a fault even though the sensor itself is fine. Replacing the sensor will not fix this, so inspect the ring whenever a sensor code returns.

3. Worn wheel bearing

Excess play in a hub bearing lets the sensor ring wobble relative to the sensor, producing a weak or erratic signal at speed. If you also hear a growl that changes with speed or feel play in the wheel, the bearing may be the real cause.

4. Wrong or mismatched tire size

The manual tells owners to install all four tires of the specified size at the proper pressure, because other sizes can make the system misread wheel speed. A compact spare, one new tire among three worn ones, or badly underinflated tires can all confuse it. Toyota's specified tire size and pressures are on the label on the driver's door jamb and in the owner's manual.

5. Blown ABS fuse

The engine-compartment fuse box has a 40 A fuse labeled "ABS NO.1" for the anti-lock brake system. A blown fuse will turn the light on and disable the whole system. If it blows again after replacement, there is a short to find, not just a bad fuse.

6. Low brake fluid or a failing actuator

Low fluid is normally shown by the red brake light, but low fluid and the ABS light together point to a leak or heavily worn pads. Much less often, the ABS actuator or its control unit fails internally. That diagnosis should come only after sensors, wiring, rings, fuse and fluid are all confirmed good.

How to Diagnose It Step by Step

1. Note which lights are on. If the red brake light is on with the ABS light, stop driving and have the car inspected.
2. Check the basics. Confirm all four tires are the correct size and pressure, the parking brake is fully released, and brake fluid is between MIN and MAX.
3. Read the ABS codes. A basic engine code reader often cannot see ABS codes. Use a scan tool that reads the ABS module, or have a shop do it. The code tells you which wheel or circuit to look at.
4. Inspect the named wheel. Follow the sensor harness from the wheel to the body connector, looking for chafing, broken clips, and green corrosion. Clean debris off the sensor tip and check the ring for missing teeth or heavy rust.
5. Test the sensor. A scan tool that shows live wheel speeds is the best test: drive slowly and compare all four readings. The wheel that reads zero or drops out is the problem.
6. Check the ABS fuse. Look at the 40 A ABS NO.1 fuse in the engine compartment.
7. Clear the code and road test. The light will usually go out once the system sees good signals again after the repair. If the same code returns, go back to the wiring and sensor ring.

What to Replace While You Are In There

ABS diagnosis often happens during brake service, and the reverse is also true: pulling the wheels to reach a sensor is a good time to measure pads, rotors and shoes. The xA uses front discs and rear drums. If the front pads are near their limit, the built-in wear indicators will squeal, and new brake pads for your car and replacement brake rotors are best done as an axle set. For drivers who want a stronger pad for spirited use, we carry EBC Yellowstuff front brake pads for the Scion xA. Rear drums on a car this age often need new brake shoes and brake hardware kits with fresh springs and adjusters.

Two cautions while working near sensors: do not let the caliper or drum hang by its hose, and route the sensor wire back exactly into its original clips so it cannot rub on the tire or suspension. A pinched sensor lead is a common cause of an ABS light appearing right after a brake job.

If you open the hydraulic system, the manual specifies SAE J1703 or FMVSS No. 116 DOT 3 brake fluid, and says to use only newly opened fluid because brake fluid absorbs moisture once the container is opened.

How Hard Is the Repair?

Checking tires, fluid and the fuse needs no tools. Replacing a wheel speed sensor is usually a simple bolt-in job once the wheel is off, though a rusted sensor can seize in its bore and take patience and penetrating oil to remove. Repairing a harness or replacing a sensor ring or wheel bearing is more involved and may require a press depending on the design. Torque every fastener to the values in the factory service manual. Actuator and control unit diagnosis is best left to a shop with a Toyota-capable scan tool. For other parts, browse our full range of brake parts.

Frequently Asked Questions

Is it safe to drive a Scion xA with the ABS light on?

If only the amber ABS light is on, the normal brakes still work, but the wheels can lock in a hard stop or on slippery roads. Drive carefully and get it diagnosed soon. If the red brake light is also on, stop and have the car inspected before driving further.

Will the ABS light turn off by itself?

Sometimes an intermittent sensor fault clears after the car is restarted, but the underlying cause is usually still there. Most stored ABS faults need to be repaired and then cleared with a scan tool.

Can new brake pads cause the ABS light to come on?

Pads themselves do not trigger it, but the work can. A sensor wire that was pinched, unclipped or stretched while the caliper was off is a common cause of a light that appears right after a brake job.

Does the ABS light affect the xA's stability control?

On xA models equipped with VSC, yes. The owner's manual says that when the ABS light is on, ABS, brake assist, traction control and vehicle stability control all stop operating.

Is there a recall for the Scion xA ABS system?

NHTSA's recall records for the xA list campaigns for the airbag control module, load-capacity labels and cruise control, but none for the brakes or ABS. An ABS light on an xA is a repair item, not a recall item.

Sources

1. Toyota - 2005 Scion xA Owner's Manual - ABS and brake warning light meanings, ABS operating speeds and self-check noise, tire size requirement, DOT 3 fluid spec, ABS NO.1 40 A fuse, VSC behavior
2. NHTSA - Toyota Safety Recall notice 18V-776 - 2004-2006 model year xA, produced late January 2003 to early January 2007
3. NHTSA - Scion xA recall records - no brake or ABS recalls listed for the xA
4. CarSpecs - 2006 Scion xA specifications - four-wheel ABS with EBD, front disc and rear drum brakes
5. Toyota Newsroom - Star Safety System - how ABS, EBD and brake assist work