C0187 is a chassis-level Diagnostic Trouble Code (DTC) that indicates a wheel speed signal plausibility issue reported by a vehicle stability or braking system. It is commonly recorded when the Anti-lock Braking System (ABS) or related stability control module sees a wheel-speed input that does not match expected behavior for that driving condition. The exact component meaning can vary by make, model, and year; confirm interpretation with basic electrical and network testing using a scan tool, multimeter, oscilloscope, and Controller Area Network (CAN) message checks before replacing parts.
What Does C0187 Mean?
This explanation follows SAE J2012 formatting and uses the standardized DTC structure; SAE J2012 defines DTC structure and some standardized descriptions, and additional standardized text is published in the SAE J2012-DA digital annex. The code shown here is C0187 without a hyphen suffix, so it is shown without a Failure Type Byte (FTB). If an FTB were present (for example C0187-1A), that suffix would identify a subtype or failure mode variant such as a specific plausibility sub-condition or quality threshold used by the manufacturer.
There is no single universal, component-level definition for many chassis codes including C0187 — interpretation varies by vehicle. C0187 is distinct because it reports a plausibility or signal-correlation fault: the control module has determined the wheel speed input is inconsistent with other inputs or expected values, rather than a straightforward open or short. Confirm by testing wiring/connectors, sensor plausibility, power/ground, and CAN/LIN messages on the specific vehicle.
Quick Reference
- System: Chassis wheel-speed signal plausibility reported to ABS/stability module.
- Typical symptom: ABS/traction control/ESC warning lamp illuminated; reduced stability operation.
- Initial checks: Scan for live wheel-speed data, check for missing or noisy CAN messages.
- Key tests: Wiring continuity, sensor voltage/resistance, oscilloscope pattern, power and ground integrity.
- Severity: Often driveable but traction and braking aids may be degraded; diagnose promptly.
Real-World Example / Field Notes
In the workshop you may see C0187 set after a wheel bearing failure, a damaged tone ring, or after a recent repair that disturbed a harness. These are commonly associated with wheel-speed sensors or their wiring, but that association depends on the vehicle architecture. One possible cause is corrosion at a connector that allows intermittent signal distortion; another possible cause is a noisy CAN bus creating implausible speed readings.
Practical observations: when you connect a scan tool you might see one wheel-speed channel frozen, erratic, or disagreeing with vehicle speed and other wheels. Using an oscilloscope often reveals an abnormal waveform (missing pulses, amplitude drop, or noise) at the sensor connector. A digital multimeter can identify open circuits or loss of sensor supply voltage; wiggle-testing the harness while observing live data can reproduce an intermittent fault.
Field note: never replace a module before proving power, ground, and signal paths are correct. If CAN messages for wheel speed are absent or corrupted, investigate the bus wiring and other nodes before assuming a local sensor fault. Always document live-data snapshots and Mode 6 or freeze-frame values where available for reference during repair.
C0187 is a chassis-level diagnostic indication tied to wheel speed signal plausibility in the Anti-lock Braking System (ABS) or related vehicle stability systems. SAE J2012 defines the general DTC structure and many standardized descriptions; actual component responsibilities and exact meanings can vary by make, model, and year. Interpretation often depends on how the vehicle manufacturer maps wheel speed sensors, sensor circuits, and message validation into the chassis controller. Always confirm the fault with electrical and network tests before replacing hardware.
Symptoms of C0187
- ABS warning lamp illuminated on the instrument cluster during startup or driving
- Traction control intervention or loss of traction control functionality under braking or acceleration
- Pulsating brake feel during slow stops or under light braking conditions
- Inconsistent speedometer readings or momentary speed jumps on the dash
- Warning messages about stability control, ABS, or sensor fault displayed
- Intermittent fault that clears after ignition cycle then returns during driving
Common Causes of C0187
Most Common Causes
- Wiring corrosion or damaged harness commonly associated with wheel speed sensor circuits
- Loose or contaminated sensor connector pins causing intermittent signal or high resistance
- Failed or marginal wheel speed sensor one possible cause when waveform is absent or noisy
- Poor power or ground supply to the ABS/ESC controller affecting signal reference
Less Common Causes
- Intermittent internal input-stage issue in the chassis Electronic Control Unit (ECU) after external tests pass
- Controller Area Network (CAN) message corruption or timeout between ABS controller and instrument cluster
- Damaged tone ring or magnetic encoder that produces implausible sensor waveforms
- Water intrusion or mechanical damage at wheel hub assemblies that affect sensor alignment
Diagnosis: Step-by-Step Guide
Tools: digital multimeter, oscilloscope, CAN-capable scan tool, backprobe pins, wiring diagrams or repair manual, jumper leads, contact cleaner, insulated pliers, non-contact voltage tester. These tools let you verify power/ground, inspect waveforms, and read live data and Mode $06 results from the ABS/ESC controller.
- Connect the scan tool and record freeze-frame data and live wheel speed values while key on; note any inconsistent or zero readings.
- Check for related chassis faults stored in module memory and verify whether C0187 includes a hyphen FTB subtype; if no FTB is present, understand the code is shown without a Failure Type Byte.
- Visually inspect sensor connectors and harness sections for corrosion, bent pins, or chafing; flex the wiring while watching live data for intermittent changes.
- Measure reference power and ground at the sensor connector with the key on; confirm voltage is within expected nominal ranges and ground has low resistance to chassis.
- Backprobe the sensor signal and use an oscilloscope to view the wheel speed waveform at slow rotation; look for clean, regular pulses and compare amplitude and symmetry to the opposite sensor or factory waveform examples.
- Perform a continuity and resistance check of the sensor circuit from connector to controller; repair any opens, high resistance, or short-to-power/ground found.
- Inspect tone ring or encoder for damage or debris; confirm physical plausibility if the waveform shows irregular gaps or amplitude dropouts.
- Check chassis module grounds and supply voltages at the ABS/ESC controller; poor supply can create implausible input readings—repair grounds or fuses as needed.
- Monitor Controller Area Network (CAN) traffic for missing or corrupted speed messages and verify wiring and terminated bus integrity if messages drop or show errors.
- After repairs, clear codes and road-test while watching live data to confirm the fault does not return; use oscilloscope and scan tool to document a correct waveform and steady CAN messages.
Professional tip: always compare suspect sensor waveforms to a known-good pattern or the opposite wheel where applicable; an oscilloscope snapshot and a short road test are more reliable than resistance alone. Only consider module-level input-stage or internal processing issues after you’ve confirmed clean power, ground, signal wiring continuity, and valid CAN messaging.
Possible Fixes & Repair Costs
Low (diagnostic/repair of wiring or connector): $50–$150. This range covers diagnostic time, cleaning or reseating connectors, repairing a short or pin repair based on continuity and voltage testing that shows an intermittent open, corrosion, or poor contact. Justify this fix when you measure correct supply voltage and ground but find intermittent signal or high resistance at a connector.
Typical (sensor or actuator replacement, single corner): $150–$450. Use this when bench or live-data testing shows an out-of-range sensor output or a failed plausibility test for that sensor while wiring and power/ground are confirmed good. Replace the sensor only after signal-level, supply, and return-path tests confirm the sensor is the fault.
High (harness repair, ABS/ESC module input-stage repair or replacement, programming): $500–$1,500+. Choose this after systematic tests show the wiring, connectors, and sensors are within spec but the module still flags the plausibility fault. Module wording: possible internal processing or input-stage issue. Confirm with scope traces, CAN data checks, and secondary bench tests before authorizing expensive module work.
Factors that affect cost: labor rates, accessibility, need for module programming, and whether multiple sensors or wiring segments require repair. Always document measured voltages, resistance, and signal waveforms to justify part replacement.
Can I Still Drive With C0187?
You can usually drive short distances with this code set, but safety systems like Antilock Braking System (ABS) and Electronic Stability Control (ESC) may be degraded or disabled depending on the vehicle. Test-driven checks — live-data showing missing or implausible wheel/attitude signals, or network messages flagged as invalid — indicate whether the vehicle’s control strategy has limited or turned off those assists. If ESC/ABS indicators are lit, avoid spirited driving and heavy braking until repaired.
What Happens If You Ignore C0187?
Ignoring this fault can leave ABS/ESC interventions reduced or unavailable, increasing stopping distances and loss-of-control risk in low-traction conditions. Faults may also worsen if a wiring short progresses or corrosion spreads, leading to intermittent failures and unexpected system behavior.
Related Codes
- C0194 – Chassis Wheel Speed Signal Plausibility
- C0193 – Traction Control Torque Request Signal Range/Performance
- C0192 – Chassis Wheel Speed Signal Plausibility
- C0191 – Traction Control Torque Request Signal Low
- C0190 – Traction Control Torque Request Signal
- C0189 – Brake Wheel Speed Signal Plausibility
- C0188 – Stop Lamp Switch Circuit Range/Performance
- C0186 – Chassis Wheel Speed Sensor Circuit Fault
- C0185 – Chassis Wheel Speed Signal Plausibility
- C0184 – Wheel Speed Signal Plausibility
Key Takeaways
C0187 indicates a chassis-level sensor signal plausibility issue often related to ABS/ESC inputs. Interpretation varies by make/model; always follow SAE J2012-DA format and confirm with measurements. Prioritize checking wiring, connectors, power, ground, and network messages before replacing sensors or modules. Replace modules only after external inputs verify good. Document test results to justify repairs and to avoid unnecessary parts replacement.
Vehicles Commonly Affected by C0187
Commonly seen on vehicles from manufacturers with complex ESC/ABS networks such as BMW, Audi, Ford, and General Motors, often reported on models with multi-sensor stability systems. These platforms use multiple wheel/attitude sensors and networked modules, so a single sensor plausibility flag can stem from wiring, connector, or CAN message issues rather than a single part failure.
FAQ
Can I clear C0187 and see if it comes back?
Yes, you can clear the code with a scan tool to check for recurrence, but clearing alone is only a diagnostic step. If the fault returns immediately or within short drive cycles, use live-data and Mode $06 (if available) to capture failing parameters. Monitor supply voltage, ground integrity, signal waveform plausibility, and CAN messages before concluding whether the fault is intermittent or persistent.
Is this code usually caused by a bad sensor?
Not usually by itself. A bad sensor is one possible cause, but the code more often points to wiring, connector corrosion, or signal-clash on the network. Only replace the sensor after bench or on-vehicle signal tests show the sensor output is out of range while power and ground are correct. Confirm with a scope trace or known-good sensor comparison where possible.
How will a technician confirm the faulty area?
A technician should perform step-by-step tests: verify supply voltage and ground at the sensor connector, measure signal voltage and waveform with a scope, check continuity and resistance of harness segments, and confirm relevant CAN messages. Replace components only when tests isolate the fault. Documenting each measurement prevents unnecessary part swaps and supports a targeted repair.
Can a software update or calibration fix C0187?
Sometimes a calibration or software update can resolve plausibility checks if the manufacturer has adjusted thresholds or corrected a logic error. However, perform full electrical verification first: software fixes are appropriate only after ruling out wiring, connector, and sensor failures. If all external inputs test good and a campaign or TSB exists for your vehicle, a software update may be justified.
How long will repairs typically take?
Minor wiring or connector repairs can take 0.5–2 hours. Sensor replacement typically 1–3 hours depending on access. Module-level diagnostics or replacement, including programming, can take several hours and may require dealer tools. Exact time depends on accessibility, modules involved, and the need for network reconfiguration; base your estimate on confirmed test findings, not guesswork.