C003B Code: Right Rear Wheel Speed Sensor Supply

1What Does the C003B Code Mean?

NHTSA report DOT HS 812 575 reproduces a selected SAE interface-code table that lists C003B as Right Rear Wheel Speed Sensor Supply with a subfault. The actual OEM description and suffix control diagnosis. The full fault record determines the test branch.

The word supply directs attention to how the sensor receives its required electrical support. It does not tell you whether the architecture uses a dedicated output, a shared circuit or another arrangement. Identify the actual sensor type and controller connection in the VIN wiring diagram. Do not assume a familiar three-wire sensor layout or import a reference-voltage specification from an engine sensor into a wheel-speed circuit.

A measurement made with the sensor disconnected may answer a different question from one made with it connected. The circuit's normal behavior and fault protection depend on its design. Record connection state, controller state and the prescribed reference point with each result. A single measured voltage without those conditions cannot distinguish a wiring defect, a load-related condition or a controller output that has changed its operating state.

The cited NHTSA table is a published reference for selected code labels, not a current repair manual. This guide does not establish a model-specific C003B repair, connector number or voltage limit. Obtain current OEM service information for the complete code. If the scan tool displays a different manufacturer description, use that description and investigate the discrepancy before applying a generic supply-circuit test.

Distinguish C003B from the adjacent C003A sensor-path and C0039 tone-wheel families in the selected mapping. A supply fault can affect usable speed information, but the presence of a speed-related companion code does not establish two independent failed parts. Save the full scan and determine the test order specified by the manufacturer. Conversely, do not dismiss a separate target fault merely because a supply concern is also present.

Preserve the module wording and suffix before clearing.

Separate C003B from adjacent fault families

2C003B Symptoms and Likely Causes

Practical cause-checking order

• Actual circuit identity: Confirm that the full OEM C003B description identifies the same supply path. Locate the actual circuit before measuring. Do not assume every vehicle exposes a separate sensor supply terminal with the same nominal voltage.
• Terminal condition: Inspect accessible connector seating, terminal condition, seals and retention. Follow approved terminal-testing methods so that probing does not spread a contact. A clean exterior does not establish that the connected circuit can operate correctly.
• Harness evidence: Check the identified harness for damage, unsuitable repairs or contact with moving components. Use the prescribed continuity, isolation or loaded test in its required connection state. A visual concern is a test lead, not a complete electrical diagnosis.
• Sensor loading: Where the OEM procedure permits isolation, compare the circuit response with the specified component connected or disconnected. Do not use an improvised jumper or bypass protection. The observed response must be interpreted against the actual architecture.
• Controller-side evidence: Verify required controller power, ground and output conditions before an internal failure decision. Follow the manufacturer's decision tree and programming or setup prerequisites. Missing scan-tool coverage cannot substitute for evidence of a failed vehicle module.

3How Serious Is C003B, and Can You Drive?

Arrange prompt brake diagnosis and follow the owner manual. Do not assume ABS or stability assistance remains available. Abnormal pedal effort, pulling, fluid loss, dragging or a red brake warning requires stopping safely and arranging recovery. The code cannot establish a safe driving distance.

Record brake warnings, pedal changes, fluid loss and recent service. Do not induce wheel slip or emergency braking to test assistance on public roads; warning-state assessment comes before any functional verification.

Follow the exact shutdown and pressure-release procedure before accessing brake components. Support a raised vehicle securely, keep clear of moving parts and never energize unidentified circuits. Do not perform public-road emergency-stop experiments.

4How to Diagnose C003B in the Right Order

1. Save the full supply fault and companions

   Capture C003B with its suffix, storing module, status and available event details. Save all companion wheel-speed, supply and communication faults before clearing. Document the warning pattern and recent service. Evaluate braking and wheel safety first. If the vehicle has abnormal pedal behavior, fluid loss, dragging or a red brake warning, arrange safe recovery instead of attempting a moving-vehicle reproduction.

2. Map the actual right-rear circuit

   Obtain the VIN-specific wiring diagram and complete-code procedure. Identify the sensor technology, relevant terminals, supply source and prescribed reference points. Determine the required controller and ignition states for each test. Do not infer a shared circuit from a generic diagram or assume that a similar code on another vehicle uses the same module connector or electrical limits.

3. Inspect connections and routing safely

   Secure the vehicle before wheel-end access. Inspect the sensor connector, cable routing, retainers and accessible harness sections affected by steering, suspension or prior work as applicable. Record contamination and damage before disturbing them. Use the specified probing and repair methods. Avoid piercing insulation or opening brake-system components when the electrical procedure does not require those actions.

4. Measure the supply under the prescribed conditions

   Follow the OEM sequence for measuring the identified supply path. Record values with their connection state and reference point. If the procedure calls for a loaded check, use the approved method and equipment. Do not apply an arbitrary external load or substitute a generic voltage specification. A measurement outside the specified conditions cannot reliably support a sensor or controller replacement decision.

5. Isolate the failed branch without bypassing protection

   Use only the isolation steps permitted by the complete-code procedure to distinguish harness, connector, sensor-load and source-side concerns. Preserve the before-and-after observations. Do not bridge protective circuits, power unidentified terminals or disconnect components while the instructions require shutdown. If the relevant circuit cannot be tested safely with available equipment, document the unresolved branch and arrange appropriate specialist testing.

6. Verify the repaired supply and wheel-speed operation

   Repair the proven defect, restore seals and cable clearance, and complete required setup. Recheck the previously failed supply test before interpreting the final wheel-speed information. Establish safe brake operation and perform the approved functional verification. Save the final module scan. If the fault was intermittent and its original condition remains untested, report that limitation rather than treating a cleared warning as a completed diagnosis.

5C003B Repairs and Cost Planning

An estimate should identify where the supply-path test failed and which repair restores that path. A terminal repair, harness repair, sensor replacement and controller procedure are separate possibilities, not a package to authorize from one code. Ask whether installation, routing, required setup and final verification are included. Any costly controller action needs its own diagnostic evidence and current service prerequisites; generic code wording cannot establish that it is necessary.

Request an itemized, VIN-specific quote for the proven repair, setup and verification. Check applicable warranty coverage.

6Using iCarsoft CR Pro S for C003B

On a supported vehicle, iCarsoft CR Pro S can save accessible faults, available freeze frame, live data and diagnostic reports. Preserve the C003B evidence before clearing.

Confirm the exact VIN, controller, requested function and software with iCarsoft before purchase. Follow OEM testing prerequisites.

7Verify the C003B Repair

After repair, verify connectors, harness clearance, setup and controller supply. Save post-repair findings, then clear only erasable records through the approved procedure. Battery disconnection is not a repair.

Run the manufacturer's applicable verification conditions in a safe workshop or route. Compare the original operating state with current data for the right-rear sensor supply path, and check current and pending faults in related modules. One clean start or idle period does not prove that every conditional monitor has completed.

Compare baseline and final scans, required setup and fault confirmation. Record whether the original event returned.

If C003B returns, compare its suffix, status, failure order and operating conditions with the saved baseline before replacing another part. Revisit the failed branch and inspect anything disturbed. Confirm the prescribed brake-system verification separately from code clearing.

8Related Brake and Wheel-Speed Code Guides

Use each related code's own diagnostic procedure.

• P0504 — Brake Switch A/B Correlation
• P0571 — Brake Switch A Circuit
• P0556 — Brake-booster pressure sensor range/performance
• P0562 — System voltage low
• U0121 — Lost communication with ABS control module
• P0500 — Vehicle-speed signal malfunction

9C003B Frequently Asked Questions

Editorial note: Diagnostic education does not replace the owner manual, current VIN-specific service information or professional inspection. Procedures, coverage and costs vary. Related guides provide context, not interchangeable repair instructions. No universal failure rate, price or outcome is implied.