2015-2016 Chevrolet Colorado ABS Light On: Common Causes and Fixes

By Core Brake Parts Tech Team — Circleville, OH warehouse

When the ABS light comes on in a 2015 or 2016 Chevrolet Colorado and stays on, the truck's antilock, traction control and StabiliTrak functions are usually shut off, but the regular brakes still work. The most common causes are a wheel speed sensor or its wiring, a damaged or rusty tone ring, a worn wheel bearing, or low brake fluid, and a scan tool that reads chassis (C) codes is the fastest way to tell which one you have.

How the ABS System Works on the 2015-2016 Colorado

Every second-generation Colorado came with four-wheel disc brakes, so there are rotors and calipers at all four corners and a wheel speed sensor reading each wheel. GM's owner manual describes the ABS as a computer that keeps receiving updates on wheel speed and separately works the brake at any wheel that is about to stop rolling. The same wheel speed signals feed Traction Control and StabiliTrak, which is why one bad sensor often lights up several warnings at once.

Two behaviors are normal and are not faults:

• The start-up check. The ABS light comes on briefly when the engine starts. As the truck begins to move, ABS tests itself, and GM notes you may hear a short motor or clicking noise and feel the pedal move slightly.
• Pedal pulsation in a hard stop. When ABS is working you may hear the pump and feel the pedal pulse. GM's instruction is to hold the pedal down firmly and not pump it.

What the Warning Lights Are Telling You

The Colorado has separate lights for ABS and for the base hydraulic brakes, and the combination matters more than any single light.

GM's own reset step is simple: if the ABS light comes on while driving, stop when it is safe, turn the truck off, and restart it. If the light stays on or comes back, the vehicle needs service. For the StabiliTrak message, the manual says to leave the engine off for at least 15 seconds before restarting.

Most Common Causes of an ABS Light

1. Wheel speed sensor or wiring

This is the number one cause on trucks of this age. The sensor sits at the hub and its harness runs along the knuckle and axle, exposed to road salt, water and rock strikes. Broken wires and corroded connectors are among the most frequent faults. A sensor that reads intermittently often sets the light only above a certain speed or over bumps.

2. Debris or rust on the sensor tip

Wheel speed sensors work across a very small air gap to a toothed tone ring. Metallic debris from worn rotors or semi-metallic pad material can stick to the sensor tip and weaken the signal. Rust building up under the sensor mounting can push the sensor out of position and change that gap.

3. Damaged or corroded tone ring

A tone ring with rusted, cracked or chipped teeth, or one with too much runout, makes the signal erratic. The module sees a wheel that seems to speed up and slow down when it does not, and it disables ABS.

4. Worn wheel bearing or hub

Play in a worn bearing lets the tone ring wobble relative to the sensor, which varies the air gap and corrupts the signal. If you also hear a growl that changes with speed, check the bearing before you replace a sensor.

5. Low brake fluid or a hydraulic problem

Low fluid turns on the brake system warning light, and when it appears together with the ABS light the problem is in the regular brakes. GM notes the fluid level drops for only two reasons: normal pad wear or a leak. Do not simply top it off; find out which one it is.

6. ABS module or hydraulic unit

Internal module or pump faults do happen, but they are less common than sensor and wiring problems. Rule out the simpler items first.

How to Diagnose It Step by Step

1. Read the codes. A basic engine-code reader will not show ABS faults. You need a scan tool that reads chassis (C) codes from the brake module. The code usually points to a specific wheel.
2. Watch live wheel speeds. Drive in a straight line at a steady low speed with the scan tool showing all four wheel speeds. A sensor that drops out, reads zero or disagrees with the others is your suspect.
3. Inspect that corner. Look at the harness for chafing, check the connector for green corrosion, and look at the sensor tip for metal buildup.
4. Check the bearing. With the wheel off the ground, rock it at 12 and 6 o'clock to feel for play.
5. Test the sensor. Depending on the sensor design, testing is done with a meter or an oscilloscope. Follow the factory service procedure for the exact test values.
6. Check fluid and the base brakes. Look at the reservoir level and inspect pads, rotors and hoses at all four wheels.

The Fix, and What to Replace at the Same Time

Most repairs are a single sensor, a harness pigtail or a hub. After the repair, clear the codes and road test; the light should go out after the start-up check and stay out.

If the corner that failed also has worn or scored rotors, this is the right time to replace them, because the sensor, hub and rotor all come apart in the same job. For the 2015-2016 Colorado we carry EBC GD Sport slotted and drilled front rotors for the Colorado and the matching EBC 3GD slotted rear rotor set. Confirm engine fit on the product page before ordering. You can also browse all brake rotors and brake pads.

A few rules to follow:

• Replace pads as axle sets. GM's manual says brake linings should always be replaced as complete axle sets.
• Use the right fluid. The Colorado's master cylinder is filled with DOT 3 brake fluid, and GM says to use only new DOT 3 from a sealed container.
• Fix whatever damaged the wiring. If the sensor wire was torn by a loose hose bracket or a seized slide, repair that too. See our brake hardware kits and brake hoses.
• Torque the wheels correctly. GM links properly torqued wheel nuts to preventing brake pulsation. Use the specification in the owner manual, in the correct sequence.

How Hard Is the Job?

Reading codes and replacing a bolt-in wheel speed sensor is a moderate DIY job with basic hand tools and a scan tool that reads ABS codes. The sensor can be seized in a rusty knuckle, so penetrating oil and patience help, and prying hard can break the sensor body inside its bore. A hub or bearing replacement is harder and needs the correct fastener torque from the service manual. If the brake system warning light is also on, or the pedal feels low or soft, treat it as a brake safety problem first and an ABS problem second.

Frequently Asked Questions

Is it safe to drive my Colorado with the ABS light on?

If the ABS light is the only light on, GM says the truck has regular brakes but no antilock function. Drive gently, leave extra following distance, and get it diagnosed soon. If the brake system warning light is on too, do not keep driving it.

Why are the ABS, traction control and StabiliTrak lights all on at once?

All three systems use the same wheel speed sensors. When the brake module loses a valid wheel speed signal, it turns off the systems that depend on it, so one bad sensor can trigger all three warnings.

Can new brake pads or rotors cause the ABS light?

They can if the sensor wire was pulled, pinched or unplugged during the job, or if the sensor was knocked out of position. Check the harness routing at the corner that was serviced before looking elsewhere.

Will disconnecting the battery clear the ABS light?

It may turn it off for a moment, but if the fault is still there the module will find it again during its self-test and the light will return. Clearing codes does not fix the cause.

Does my 2015 Colorado have an ABS recall?

The 2015 Colorado and Canyon were covered by GM safety recall 15595 for a loss of power steering assist caused by a torque-sensor connector, which is a steering issue, not an ABS one. Check your VIN at nhtsa.gov for any open recalls on your specific truck.

What brake fluid does the 2015-2016 Colorado use?

GM specifies DOT 3 brake fluid from a new sealed container. Using the wrong fluid can keep the brakes from working properly.

Sources

1. 2015 Chevrolet Colorado Owner Manual (GM) - ABS and brake warning light meanings, reset steps, ABS self-test, StabiliTrak messages, DOT 3 fluid, axle-set linings
2. GM Stop Delivery Order for Safety Recall 15595 (NHTSA) - 2015 Colorado and Canyon power steering recall details
3. First Drive of 2015 Chevrolet Colorado and GMC Canyon (Clean Fleet Report) - standard four-wheel disc brakes with ABS and StabiliTrak
4. Diagnosing Wheel Speed Sensors (Brake and Front End) - air gap, debris, tone ring and wiring failure causes and test methods