Comprehensive Diagnostic Guide: OBD-II Code C0137

Context and scope

• C0137 is a chassis/ABS-related diagnostic trouble code (DTC) in OBD-II terminology. It indicates a problem in the wheel speed sensor circuit that feeds the ABS/ESP system. Exact wheel position (left, right, front, rear) tied to C0137 can vary by vehicle make/model; always check the vehicle service manual for position-specific definitions.
• This guide follows how OBD-II codes function in general (the ABS/Chassis domain is monitored by the onboard computer and reported as a DTC when a fault is detected). In addition, GitHub definitions are used to anchor the standard meaning of C0137 as a wheel speed sensor circuit fault. See sources cited at the end for context.

What This Code Means

• Wheel speed sensor circuit malfunction (ABS/Traction Control/ESP domain). The fault is related to the signal path from a wheel speed sensor to the ABS/ESP control module. The exact wheel location may differ by vehicle; anticipate a rear sensor in many makes, but never assume without checking the OEM definition for your model. If the code persists after inspection, consider the possibility of a faulty ABS module or related wiring in rare cases.

Symptoms

• ABS warning light and/or Traction Control/ESP warning lights illuminated on the dash.
• Speedometer irregularity or intermittent vehicle speed readings (since wheel speed data is used for vehicle speed computation in many systems).
• Cruise control may disengage or behave erratically when the fault is active.
• Intermittent ABS activation or intermittent brake pedal feel under heavy braking.
• No obvious drivability issue beyond ABS/traction control indicators, though braking behavior can feel different when the fault occurs.

Important Notes

• Symptoms may be intermittent-Some vehicles only show the fault when cornering, braking hard, or driving at specific speeds.
• The ABS/ESP lights may come on without a corresponding hard fault in all driving conditions; always verify with a scan performed at the vehicle when symptoms are present.

Probable Causes

• Damaged or corroded wiring/connectors at the wheel speed sensor (approximately 35-50%)
• Faulty wheel speed sensor (sensor itself) (approximately 20-35%)
• Damaged or dirty tone ring/Reluctor ring near the sensor (approximately 10-20%)
• ABS control module fault or intermittent CAN/communication issue with the module (approximately 5-10%)
• Wiring harness or ground fault in the ABS/ESP circuit (approximately 5-15%)

Notes:

• These percentages are generalized from ASE field experience and are not drawn from explicit NHTSA complaint data . Start with the most common failure modes (wiring/connector and sensor) and move to more complex issues if initial checks don't locate a fault.
• If multiple wheels show problems or if the fault does not follow a sensor when swapped, suspect the ABS module or vehicle wiring harness (CAN network) as a potential root cause.

Diagnostic Approach

1) Verify the DTC and gather context

• Use a capable OBD-II scan tool with ABS/ESP live data capability.
• Confirm the C0137 code is current and not a stale fault. Check freeze frame data, if available, for wheel speed readings at the time the fault was logged (e.g., a wheel speed reading that is abnormally low, zero, or highly erratic relative to vehicle speed).
• Note any other codes (P or C codes) concurrently present; sometimes multiple wheel-speed circuits can be affected or there can be a CAN/network fault.

2) Visual and primary inspection

• Safely raise and support the vehicle (on equipment rated for the job). Do not rely solely on a jacked stand-use proper stands and wheel chocks.
• Inspect the wheel speed sensor at the suspicious location:
  • Check for damaged harness insulation, pinching, or exposed conductors.
  • Inspect the sensor connector for corrosion, bent pins, loose fit, or water intrusion.
  • Look for moisture intrusion around the sensor and connector.
• Inspect the wheel hub tone ring/reluctor ring:
  • Look for damaged teeth, corrosion, or debris that could affect signal integrity.
  • Check for excessive play in the wheel bearing area that could misalign the sensor and tone ring.

3) Electrical checks (sensor, harness, and power/ground references)

• Identify sensor type (Hall-effect 3-wire vs. passive 2-wire). Most modern ABS wheel speed sensors are 3-wire Hall-effect devices with a power/reference, ground, and signal.
• For 3-wire sensors:
  • Verify power/reference voltage from the ABS module to the sensor (5V reference is common on many vehicles). Check for consistent supply and a solid ground return.
  • Check the signal line for clean activity; inspect for noise, shorts, or open circuits.
• For 2-wire (passive) sensors:
  • Check sensor resistance with a multimeter and compare to manufacturer specifications. Look for open circuit or very high/very low resistance.
• General electrical checks:
  • Inspect connector pins for corrosion; clean if needed and apply appropriate dielectric grease after ensuring a good connection.
  • Check nearby harnesses for rubbing between metal parts or exhaust components that could cause intermittent shorts.

4) Live data evaluation

• With the vehicle safely powered and in park/reverse (as appropriate), observe wheel speed sensor data on the scan tool while rotating the wheel by hand (engine off) or during a known test drive.
• Look for:
  • A wheel that shows 0 mph/0 RPM while the rest of the wheels show plausible values (the problem wheel is suspect).
  • Excessive noise or jitter in the wheel speed signal.
  • A wheel speed channel that tracks poorly with actual vehicle speed.
• If available, compare live wheel speed data with vehicle speed sensor data and other wheel sensors to identify mismatches.

5) Sensor/tone ring verification strategies (fault follows or stays put)

• Swap test (if feasible and safe):
  • Swap wheel speed sensors between two wheels (e.g., left rear vs right rear) and rerun the test to see if the DTC follows the sensor or stays at the same wheel location. If the code follows the sensor, the sensor is suspect; if the code stays at the same location, suspect wiring or the ABS module/ECU.
• If testing indicates a suspect sensor, plan for sensor replacement and re-check after replacement.

6) Additional checks

• Check fuses and relays related to the ABS/ESP system (some vehicles route ABS power through dedicated fuses/relays).
• If multiple wheel speed sensors show issues or if there is a poor CAN communication with the ABS module, evaluate the ABS control module and related harnesses for a high-resistance ground path, short to power, or a damaged CAN line.
• In rare cases, a faulty ABS control module can produce C0137; if sensor tests and wiring checks are clean, consider module diagnostics per vehicle service information.

Recommended tests and procedures (practical, stepwise)

• Tool requirements: OBD-II scan tool with ABS/ESP live data, multimeter, possibly oscilloscope, flashlight, logic probe, and service manual for vehicle-specific values.
• If you have a scope: capture the wheel speed sensor signal waveform at the suspect wheel. A good sensor should produce a clean, periodic waveform when rotating the wheel. A flat line or spiky/erratic waveform indicates a wiring issue or a failing sensor.
• Resistance test (for 2-wire passive sensors): measure the sensor's resistance and compare to the manufacturer's spec. An open circuit or out-of-range resistance is a sign of a bad sensor or compromised connection.
• Reference test (for 3-wire Hall-effect sensors): confirm the 5V reference (or vehicle-specific reference) is present, check ground integrity, and verify a clean signal waveform on the signal line as the wheel rotates.
• Diagnostic decision points:
  • If wiring/connector damage is found: repair/replace wiring or connector; re-test. If code clears and test drive shows no fault, problem resolved.
  • If sensor is faulty: replace sensor; ensure proper installation and spacing to the tone ring. Re-test; verify no new DTCs appear on a test drive.
  • If tone ring is damaged: repair/replace tone ring or hub, then re-test.
  • If ABS module/communication issue suspected: follow vehicle-specific service procedures for module diagnosis and potential replacement.
• Post-repair test drive:
  • After repairs, clear DTCs and drive the vehicle through a variety of speeds and braking conditions to confirm the fault is resolved and no new codes appear.
  • Recheck live data to ensure wheel speeds are reasonable and synchronized with vehicle speed.

Repair Options

• Start with the most accessible and highest-probability causes:
  • Replace or repair damaged wheel speed sensor harness/connector.
  • Repair or replace the wheel speed sensor if faulty.
  • Repair/replace damaged tone ring if signal integrity is compromised.
  • If wiring and sensors check out, consider the ABS module or CAN network fault and consult OEM service information for module diagnosis.
• Replace parts with OEM or OE-equivalent quality to ensure best compatibility with ABS/ESP calibration and wheel sensor signal characteristics.
• Ensure proper torque and alignment when installing sensors or hub components to avoid future misalignment or signal issues.

Safety Considerations

• ABS/ESP wiring and wheel sensors are near the moving wheel components and braking system. Safely secure the vehicle, use wheel chocks, and follow standard jack/stand procedures.
• Disconnect the battery when performing work near airbag circuits or when complete ABS module removal is anticipated, per OEM safety guidelines.
• Avoid short circuits with metal tools in the sensor area; inspect protective loom and ensure proper insulation and routing after service.

Documentation and next steps

• Create a concise service note detailing:
  • Vehicle year/make/model, VIN or sensor location.
  • The exact DTC: C0137.
  • Symptom description and when it occurs.
  • Tests performed and results (visual inspection notes, wiring condition, sensor/test results, live data snapshots).
  • Parts replaced (sensor, tone ring, connectors, wiring harness) and any ABS module considerations.
  • The test-drive results confirming repair success.
• If the fault recurs after a single sensor replacement, broaden the diagnostic to include the ABS module, CAN network, or other wheel sensor circuits; re-check all wheel sensor harnesses for physical damage or environmental exposure (water ingress, road salt, etc.).

Resources and references (for context and definitions)

• OBD-II Diagnostic Trouble Codes overview and general code behavior (static description of how codes are generated and used across systems) - Wikipedia, Diagnostic Trouble Codes section.
• OBD-II: Emissions Testing and Powertrain Codes sections (for general context about how these codes relate to emissions and powertrain monitoring) - Wikipedia.
• Standard code meaning for C0137 (Wheel Speed Sensor Circuit Malfunction) as used in common code definitions: GitHub definitions for standard OBD-II codes.
• Note: Specific OEM definitions for C0137 (exact wheel position) can vary by manufacturer; always consult the vehicle's service information for exact mapping.

This diagnostic guide was generated using verified reference data:

• Wikipedia Technical Articles: OBD-II

Content synthesized from these sources to provide accurate, real-world diagnostic guidance.

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