2015 Ford Explorer ABS Light On: Diagnosing a Right Rear Wheel Speed Sensor Code (C003A)
Introduction
ABS and traction control issues can be frustrating, especially when the problem seems straightforward—like a wheel speed sensor code—but keeps coming back. In this case, I worked on a 2015 Ford Explorer with an ABS warning and a stored fault pointing to the right rear wheel speed sensor. What looked like a simple sensor issue turned into a deeper diagnostic process that highlights why proper testing always beats guesswork.
Let’s walk through how I approached it and what actually fixed the problem.
Vehicle Concern
The vehicle is a 2015 Ford Explorer 3.5L. The customer complaint was:
ABS light illuminated
Traction control light on
Intermittent stability control warnings
The vehicle still drove fine, but the warning lights were persistent.
Initial Inspection & Symptoms
First thing I always do is verify the concern:
Lights were on as described
No obvious drivability issues
No abnormal noises from the rear
I also did a quick visual check around the right rear wheel area since that’s where the system was pointing. Nothing immediately obvious—no broken wires hanging or connectors unplugged.
At this point, it was time to hook up the scan tool and see what the system was actually telling us.
Diagnostic Trouble Codes
The ABS module had two stored codes:
C003A:01-AB — Right Rear Wheel Speed Sensor: General Electrical Failure
U3003:16-68 — Control Module Battery Voltage
What These Codes Mean
C003A is the main issue here. It tells us the ABS module is not getting a proper signal from the right rear wheel speed sensor circuit.
The “:01” portion indicates a general electrical failure—this could be:
Open circuit
Short
No signal
Corrupted signal
The second code, U3003, relates to battery voltage. In most cases, this is a history or secondary code triggered by:
Low voltage during cranking
Battery replacement
Temporary voltage fluctuation
Since system voltage was reading normal (around 14.3V), I didn’t consider this the primary issue.
Diagnostic Process
This is where a lot of techs go wrong—they see a wheel speed sensor code and immediately replace the sensor. That works sometimes, but on these Explorers, it’s not always that simple.
Here’s how I broke it down step by step.
Step 1: Check Live Wheel Speed Data
Instead of guessing, I pulled up live data from the ABS module and monitored all four wheel speeds.
This is one of the fastest ways to narrow things down.
What I was looking for:
Does the right rear sensor read at all?
Is it consistent with the other wheels?
Does it drop out intermittently?
Sure enough, the right rear wheel speed was either reading 0 mph or dropping out intermittently, while the other three wheels were stable.
That tells me right away:
👉 The ABS module is telling the truth
👉 The issue is isolated to that corner
Step 2: Visual Inspection of Sensor and Harness
Next, I went back to the right rear and did a closer inspection.
Key areas I always check:
Sensor connector
Wiring near the knuckle (common flex point)
Routing along the control arm
Things I’m looking for:
Broken insulation
Corrosion
Loose or damaged connectors
Evidence of previous repairs
In this case, the sensor looked like it may have been replaced before, which raised a red flag. That often means someone already tried the “easy fix.”
The wiring looked okay—no obvious damage—but that doesn’t rule it out completely.
Step 3: Sensor Signal Check
At this point, I needed to know whether the sensor was actually producing a signal.
You can do this a couple of ways:
Backprobe and watch signal with a scope
Measure AC voltage while spinning the wheel
Or monitor scan data while manually rotating the wheel
I chose the practical route—spinning the wheel and watching live data.
Result:
Signal was inconsistent
Sometimes present, sometimes completely gone
This is key.
If the sensor were completely dead, you'd expect no signal at all. Intermittent signals usually point to something mechanical affecting the reading.
Step 4: Consider the Tone Ring (Critical on This Platform)
Here’s where experience with these vehicles matters.
On the 2015 Explorer, the tone ring is built into the rear wheel hub assembly. You can’t service it separately.
Common failure modes:
Cracked tone ring
Rust swelling inside the hub
Signal distortion due to internal damage
When that happens, the sensor can’t read the wheel speed correctly—even if the sensor itself is brand new.
Given that:
The sensor may have already been replaced
The signal was intermittent
No wiring faults were obvious
👉 The hub assembly became the top suspect.
Key Findings
After going through the diagnostics, here’s what stood out:
Right rear wheel speed signal was erratic
Sensor had likely been replaced previously
No clear wiring faults found
Issue behavior matched a failing tone ring inside the hub
This lined up perfectly with a known pattern on these Explorers.
Final Diagnosis / Recommendation
Failing right rear wheel hub assembly (integrated tone ring issue).
Recommended Repair:
Replace the right rear wheel hub assembly
Inspect connector and wiring during replacement
Clear codes and verify repair with live data
Once the hub is replaced, the tone ring issue is eliminated, and the sensor should produce a clean, consistent signal.
Common Causes of This Issue
This type of ABS code isn’t unique to this vehicle. Here are the most common causes across many makes and models:
Failed wheel speed sensor
Damaged or corroded tone ring
Wheel hub bearing failure (integrated tone ring designs)
Broken or chafed wiring near suspension components
Connector corrosion or poor pin fit
Debris buildup affecting sensor reading
On Ford Explorers specifically (2011–2019), rear hub failures are extremely common.
Tools Used
Professional scan tool (for ABS data and codes)
Basic hand tools for inspection
Optional: multimeter or oscilloscope
Tips for DIYers or Buyers
If you're tackling this yourself or inspecting a used vehicle:
For DIYers:
Always check live wheel speed data before replacing parts
Don’t assume the sensor is bad—verify the signal
Inspect wiring closely where it flexes with suspension
For Used Car Buyers:
Watch for ABS or traction control lights
Test drive and look for warning messages
Scan the vehicle if possible—ABS codes can hide expensive issues
Conclusion
This case is a perfect example of why diagnostics matter. A simple code for a wheel speed sensor doesn’t always mean the sensor is the problem.
By checking live data, understanding common failure patterns, and taking a logical approach, we avoided replacing unnecessary parts and went straight to the root cause.
On these Explorers, the rear hub assembly is often the real culprit—and knowing that can save a lot of time and frustration.
Call to Action
If you're buying a used vehicle, having a solid inspection strategy can save you thousands. Check out my Used Car Inspection Guide to help you make a smart purchase.
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