C0037 — Left Rear Wheel Speed Sensor (Subfault) #

Note: The description of this DTC (Diagnostic Trouble Code) may vary depending on the manufacturer.

• Left Rear Wheel Speed Sensor Circuit Malfunction (GM, Ford, Toyota)
• Left Rear ABS Wheel Sensor Signal Fault (Nissan, Honda)
• Left Rear Wheel Speed Sensor Electrical Error (BMW, Mercedes-Benz)

Summary of C0037 #

The C0037 code indicates a problem detected by the vehicle’s ABS (Anti-lock Braking System) control module regarding the left rear wheel speed sensor. The sensor is responsible for monitoring the rotational speed of the left rear wheel and transmitting this information to the ABS module. If the sensor signal is missing, erratic, or falls outside the expected range, the control module logs this code. The “subfault” designation typically means there’s an additional specific detail about the nature of the malfunction, such as an electrical issue, poor signal, or intermittent connection. This fault can affect ABS operation, traction control, and stability systems.

Common Symptoms for DTC C0037 #

When C0037 is present, you may notice a variety of warning signs—some subtle, others more pronounced. Since the ABS relies on accurate wheel speed data to operate, a faulty sensor can undermine key safety features. Common symptoms include:

• ABS warning light illuminated on the dashboard
• Traction control or stability control warning lights
• Loss of ABS function (wheels may lock during hard braking)
• Unusual braking behavior, especially on slippery surfaces
• In some cases, speedometer fluctuations or malfunction

Probable Causes of C0037 (in order of likelihood) #

Several factors may trigger the C0037 code. Here’s a rundown, ordered from most to least likely based on field experience and OEM technical bulletins:

1. Faulty left rear wheel speed sensor (most common; often due to water intrusion, impact, or age)
2. Damaged or corroded sensor wiring (wire harness issues, broken connectors, pinched wires)
3. Failed or loose sensor reluctor ring (the toothed ring attached to the wheel hub that the sensor reads)
4. Contaminated sensor tip (metal debris, road grime interfering with signal)
5. ABS control module malfunction (rare, but possible if other sensors show similar issues)

Step-by-Step Diagnostic Process for C0037 #

Diagnosing a C0037 code requires a systematic approach to avoid unnecessary part swaps and ensure the root cause is addressed. Here’s a proven workflow:

• 1. Verify the code and clear it: Use an OBD-II/EOBD scanner to confirm C0037 is active. Clear the code and perform a short test drive to see if it returns.
• 2. Inspect the left rear sensor and wiring: Visually check the sensor, harness, and connector for obvious signs of damage, corrosion, or disconnection.
• 3. Check sensor signal with a scan tool: Observe live data for the left rear wheel speed sensor. Look for values that are out of sync with the other wheels or dropouts during wheel rotation.
• 4. Test continuity of sensor wiring: Using a multimeter, verify there’s no open circuit or short between the ABS module and the sensor connector.
• 5. Inspect the reluctor ring: Check for broken, cracked, or missing teeth on the tone ring. Ensure it rotates smoothly with the wheel.
• 6. Swap sensors (if possible): Temporarily swap the left rear sensor with another wheel to see if the problem follows the sensor. This isolates sensor vs. wiring/module issues.
• 7. Assess ABS module (if all else checks out): If wiring and sensors are sound, the module may be at fault; further OEM-specific tests may be required.

Possible Repairs for C0037 #

Once the cause is identified, repairs can restore proper ABS and stability control operation. Here are the most common solutions, matched to the likely causes:

• Replace the left rear wheel speed sensor if it is found to be faulty or giving erratic readings.
• Repair or replace damaged sensor wiring or connectors, ensuring all connections are clean and secure.
• Install a new reluctor ring if the existing one is damaged or missing teeth.
• Clean the sensor tip and surrounding area to remove any metallic debris or dirt interfering with signal transmission.
• If all sensors and wiring check out, consider replacing or reprogramming the ABS control module (rare; consult OEM procedures first).

Is It Safe to Drive with C0037? #

Limited—Cautious Driving Only. While the basic braking system will still function, ABS, traction control, and stability aids may be disabled. This means in emergency stops or slippery conditions, the risk of wheel lockup and loss of control is higher. It is strongly recommended to have the issue addressed as soon as possible, especially before driving in adverse weather.

Vehicles Most Commonly Affected by C0037 #

This code appears across a wide range of vehicles equipped with four-wheel ABS systems. Some platforms where it is frequently reported include:

• Chevrolet Silverado, Tahoe, and Equinox
• Ford F-150, Explorer, and Escape
• Toyota Camry, Corolla, and RAV4
• Honda Accord and Civic
• Nissan Altima and Rogue
• BMW 3 Series and X5
• Mercedes-Benz C-Class and E-Class

Regardless of make, any modern vehicle utilizing individual wheel speed sensors for ABS/ESC can potentially log C0037.

Common Mistakes & Best Practices for C0037 #

Even seasoned technicians can stumble on this code. Avoiding common pitfalls makes for faster, more reliable repairs:

• Assuming the sensor is always at fault—sometimes the wiring or connector is the true culprit.
• Neglecting to check the reluctor ring for physical damage or debris.
• Overlooking the importance of clearing the code and retesting after each repair step.
• Failing to use OEM-grade replacement parts—aftermarket sensors may not provide the correct signal profile.
• Skipping the scan tool live data step—comparing all wheel speeds helps pinpoint intermittent faults.

Express FAQ about C0037 #

When it comes to wheel speed sensor codes, drivers and techs often have quick questions:

• Q: Can a bad wheel speed sensor cause my car to go into limp mode?
  A: Not typically. Most vehicles will only disable ABS/traction control, not engine power, for this code.
• Q: Will replacing the sensor always fix C0037?
  A: Not always. If the issue is with wiring, the reluctor ring, or even the ABS module, the code may persist until the root cause is addressed.