Honda Element ABS Light On

A few days ago, Makshvac in our Ask a Mechanic forum asked about the ABS light on his Honda Element. Specifically, he wanted to know how to test the sensor and also the wheel bearing hub assembly to find the source of the light.

While we're specifically going to talk about the Element today, this applies to many vehicles with anti-lock braking systems. When the ABS light comes on, it can be one of several things triggering it.

An intermittent light may mean moisture is interfering with the sensor or a loose wire or connection from the sensor.

A constant light indicates a specific fault with the ABS system and will require diagnostics, but will usually have also triggered an engine (PCM) error code that can be retrieved to narrow down the likely culprit.

No light at all including at vehicle startup (when key is in "on") will indicate a fault in the ABS light and warning system itself.

In Maks' case, we're talking about a continually lit ABS warning light. Although he didn't specify which wheel, the procedure for narrowing down the problem is generally the same no matter which wheel it indicates. Things only change if the wheel hub is the source of the problem.

Start With the Easy Stuff

Check the brake fluid levels and, if possible, the brake pad thicknesses. Make sure your vehicle doesn't have more than one brake fluid reservoir (some have one for the manual booster and another for the ABS pump) and if it does, be sure they're all filled to the full line. Make sure the fluid itself isn't bad and in need of flushing and replacement (often a sign of worse problems).

Brake pads should be inside safety limits for thickness. If you aren't sure how thick they should be, take them to a professional. Brakes are too important to fool around with if you don't know what you're doing.

Narrowing Down the Problem

First, as always, check the computer for codes. You can pull them using a code reader (more here), diagnostic computer, or manually with the key-on-off-on-off method (detailed here).

The code given will likely narrow down which sensor or relay is triggering the warning. The better code readers can also read the ABS Module directly and give even more specific information.

There are sensors on each wheel (usually a "speed sensor" and often a hub or "wobble" sensor, among other possibilities). There is also at least one sensor for the ABS pump (which automatically "pumps" the brakes in the "ABS stutter" that defines what this braking system does). There is also probably a fluid level/pressure sensor and could be others as well. Knowing which sensor is triggering the error goes a long way towards narrowing down the location of the problem.

If you have no access to the PCM or ABS-M, then circuit testing is going to be a long and tedious process.

The Trigger Is Not Necessarily the Problem

Just because a sensor triggered the error, however, does not mean that sensor is the home of the problem. It's just the closest in line to the ABS-M, so the problem could be there or anywhere behind it.

This is why, once you've narrowed the geographic location of the problem on the car, you will need to manually test each component from the error trigger back to the wheel itself.

Fix It

Sounds simple, right? Once you know the source of the problem, fix it. Like this means replacing a sensor, fixing whatever triggered the sensor, or repairing wiring/fuses/relays in the ABS circuits.

Now reset the computer and see if all is OK. Find out more about ABS Repair here.