C0037 on 2015-2016 Ram 1500: Left Rear Wheel Speed Sensor Causes and Fixes

What's Unique About the 2015-2016 Ram 1500

On 4th Generation Ram trucks, the wiring harness for the rear wheel speed sensors is notoriously exposed to the elements and potential physical damage from road debris or suspension movement. As a result, this code is frequently caused by a damaged wire or corroded connector rather than a failure of the sensor itself. A common chafe point is where the harness runs along the frame rail, sometimes rubbing through near the fuel tank or in the driver's side front wheel well where it passes through to the ABS module. Manufacturer documents specifically advise technicians to inspect the wiring harness thoroughly, even opening the convoluted tubing to check for hidden damage, before replacing any parts.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Symptoms You May Notice

• ABS warning light illuminated
• Traction Control or Electronic Stability Control (ESC) warning light illuminated
• Cruise control may not function
• "Service ABS System" or similar message on the instrument cluster
• "Service 4WD System" message and/or 4WD system is disabled

Most Likely Causes

1. Damaged or Corroded Wheel Speed Sensor Wiring/Connector 🔴 High Probability → Shop ABS Wheel Speed Sensor The wiring harness is routed along the frame and axle, making it susceptible to damage from road debris, moisture, and flexing. FCA has issued documents advising technicians to check for this specific issue, as breaks can occur anywhere along the harness, including above the fuel tank.
   How to confirm: Visually inspect the entire length of the wiring harness from the left rear wheel hub to where it joins the main harness. Look for chafing, cuts, pinch points, or green corrosion inside the connector. Open the convoluted tubing in suspect areas. A continuity test with a multimeter from the sensor connector to the ABS module connector is the most definitive test.
   Typical fix: Repair the damaged section of wire using weatherproof splices and heat shrink tubing. If the connector is corroded, it may need to be cleaned or replaced with a pigtail connector.
   Est. part cost: $10-$30
2. Faulty Left Rear Wheel Speed Sensor 🔴 High Probability → Shop ABS Wheel Speed Sensor The sensor is an electronic component located at the wheel hub, where it is exposed to heat, vibration, and moisture, leading to eventual failure. Debris can also accumulate on the magnetic tip, causing erratic readings.
   How to confirm: After confirming the wiring is good, use a scan tool to watch the live data from the sensor while spinning the wheel; if the reading is erratic or doesn't change, the sensor is likely bad. You can also swap the left and right rear sensors; if the code changes to C003A (Right Rear Wheel Speed Sensor), the sensor is confirmed bad. Resistance for a good sensor should be between 800 Ω – 1.2 kΩ. 🎬 See how to test and replace the rear sensor.
   Typical fix: Replace the left rear wheel speed sensor. It is typically held in by a single 8mm or 10mm bolt.
   Est. part cost: $25-$70
3. Damaged or Debris-Covered Tone Ring ⚪ Low Probability The tone ring, which the sensor reads, is part of the axle or wheel bearing assembly. While durable, it can be damaged by severe impacts or become obstructed by mud, rust, or metallic shavings from a failing bearing.
   How to confirm: Visually inspect the tone ring for missing teeth, cracks, or heavy rust/debris. This may require removing the wheel speed sensor to see the ring. Check for play in the wheel bearing, as excessive movement can alter the sensor-to-ring air gap.
   Typical fix: If the tone ring is part of the axle shaft, the shaft must be replaced. If it's part of the wheel hub/bearing assembly, that assembly needs to be replaced.
   Est. part cost: $150-$400

Rare But Worth Checking

• Faulty ABS Control Module: → Shop ABS Control Module This is the least likely cause and should only be considered after all other possibilities (sensor, wiring, tone ring) have been definitively ruled out. A faulty module is expensive and often requires programming by a dealer.

Diagnosis Steps

1. Read the fault codes with an ABS-capable scan tool. Note any suffixes to the C0037 code (e.g., -1D, -2F).
2. Perform a thorough visual inspection of the left rear wheel speed sensor's wiring harness and connector. Open the loom and check for chafing against the frame, suspension components, or above the fuel tank.
3. If the wiring looks good, use the scan tool to monitor live data from all four wheel speed sensors while driving slowly in a straight line. The reading for the left rear should be erratic, zero, or significantly different from the others.
4. If live data is inconclusive, swap the left and right rear wheel speed sensors. Clear the codes and drive again. If the code changes to C003A, the sensor is faulty. If C0037 returns, the problem is in the wiring or ABS module.
5. If the sensor is suspected, test its internal resistance with a multimeter. A reading between 800 Ω and 1.2 kΩ is typical.
6. If wiring is suspected, check for voltage and ground at the sensor connector with the ignition on. Then, perform a continuity test on the signal and ground wires from the sensor connector back to the ABS module connector to find any open circuits or shorts.
7. Inspect the tone ring on the axle for damage, debris, or excessive rust.
8. If the sensor, wiring, and tone ring are all confirmed to be good, the issue may be with the ABS control module, which requires professional diagnosis.

Parts You'll Likely Need

• Rear Wheel Speed Sensor (OEM #68231044AE (replaces 68053861ab, 68053861ac, 68053861ad, 68231044aa, 68231044ab, 68231044ad)) — This is one of the two most common failure points for this code. It is an electronic component that fails due to heat, age, and vibration.
  Trusted brands: Mopar, Standard Motor Products (SMP), Dorman, Bosch, NTK
  OEM price range: $35-$55
  Aftermarket price range: $25-$50
• Wheel Speed Sensor Connector Pigtail (OEM #68064999AA (Note: This is a generic 3-way pigtail and may require modification)) — If the wiring is damaged or corroded at the connector, replacing the connector pigtail is the standard repair.
  Trusted brands: Mopar, Dorman
  OEM price range: $20-$40
  Aftermarket price range: $10-$25

Related Codes That Often Appear With This One

• C003A — This code is for the Right Rear Wheel Speed Sensor. If both appear, it may point to a wiring harness issue common to both rear sensors, as noted in STAR Case S2005000003.
• U0403 — Implausible Data Received from Transfer Case. This can be set as a secondary code when the ABS module, which provides wheel speed data, is faulted.

Technical Service Bulletins (TSBs) & Recalls

• 68292756A$: Confirms multiple manufacturer-specific definitions for C0037 on Ram trucks, including 'Circuit Current Out of Range' and 'Signal Erratic'.
• S2005000003: This is a STAR Case, not a TSB, but it's a critical document. It explicitly links C0037-1D to wiring damage and corrosion and advises technicians to open the harness loom for inspection.

Platform-Specific Known Issues

• A STAR Case document (S2005000003) from the manufacturer highlights that code C0037-1D is often caused by corrosion or damage to the wheel speed sensor wiring, and instructs technicians to inspect the harness carefully, even if it looks undamaged from the outside.
• In a YouTube video by 'JL's Auto Solution' on a 2015 Ram, the C0037-1D code was traced to a wiring issue, not a faulty sensor, demonstrating the importance of testing the circuit before replacing parts.
• A user on Reddit with a 2019 Ram reported codes C0037-2F and C0037-1D, replaced the sensor, but the issue persisted, pointing to a likely wiring fault.

Mechanic-Grade Diagnostic Values

• Wheel Speed Sensor (Hall-Effect Type) Signal Voltage — expected: A digital square wave switching between approximately 10.4V and 10.8V when the wheel is spun. Requires an oscilloscope.. Failure: A flat line, a voltage that doesn't switch, or a voltage significantly lower than the ~12V bias voltage from the ABS module.
• Wheel Speed Sensor Circuit Bias Voltage — expected: ~12V at the sensor connector with the key on.. Failure: This is a low-current bias voltage. Using an incandescent test light will pull the voltage to ground, which is normal. A reading of 0V with a multimeter indicates an open circuit in the harness or a fault in the ABS module.
• Wheel Speed Sensor Resistance — expected: 800 Ω – 1.2 kΩ.. Failure: A reading outside this range (e.g., open loop or shorted) indicates a faulty sensor.

Scan Tool Commands That Help

• wiTECH (Dealer Tool) or AlfaOBD/Autel (Advanced DIY): ABS Initialization — This procedure is required after replacing the ABS control module to configure it to the vehicle and calibrate the system. It may also be necessary after a flash update.
• wiTECH (Dealer Tool) or AlfaOBD (Advanced DIY): Write VIN to Module — When installing a used or new ABS module, the vehicle's VIN must be programmed into it. Some tools like Autel may fail on used modules, while wiTECH or AlfaOBD can often succeed.

Wiring & Ground Locations

• Left Rear WSS Wires — The harness runs from the left rear wheel hub, along the frame rail, often passing over the fuel tank, and into a larger chassis harness that goes to the ABS module under the driver's floor.. This harness is a known weak point. The section above the fuel tank is prone to corrosion, and the section along the frame rail is prone to chafing, causing open or shorted circuits that trigger C0037.
• ABS Module Connector Pins (Left Rear) — On the main connector at the ABS module (driver's side frame rail). The wires are typically Dark Green/Gray and Dark Green/Yellow.. These are the termination points for testing the entire circuit's continuity and resistance from the module side. A good reading here but a bad one at the sensor proves the fault is in the harness.
• Chassis Ground (G905A as an example) — There are multiple chassis grounds. One key ground point is on the frame in the driver's side wheel well, forward of the upper control arm. Another is on the core support near the battery.. A poor ground connection for the ABS module or related components can cause erratic behavior and various electrical fault codes, including C0037. Verifying main grounds are clean and tight is a crucial step in diagnosing electrical issues.

Real Owner Repair Stories

• YouTube channel 'DiagnoseDan' (2016 Ram 3500 (similar wiring/issue to 1500)) — ABS, 4x4, and check engine lights on. Code C0037-1D (Circuit Out of Range) was active.
  ❌ Tried (didn't work) Customer replaced the left rear wheel speed sensor.
  ✅ What actually fixed it A diagnostic check found 11.8V at an inline chassis connector under the driver's floor, but 0V at the sensor connector. This identified an open circuit in the wiring harness between the two points, which was then repaired.
• YouTube channel 'JL's Auto Solution' (2015 Ram 1500) — ABS light on, code C0037-1D (Circuit Current Out of Range).
  ❌ Tried (didn't work) Initial diagnosis pointed towards the sensor, but testing proved it was not the root cause.
  ✅ What actually fixed it The technician found a broken wire inside the harness loom in the driver's side front wheel well area where the harness passes through. Repairing the broken wire resolved the code.
• Reddit user 'Ty9121' (2019 Ram 1500 5.7L) — ABS, Traction control disabled, 4WD unavailable messages. Codes C0037-2F and C0037-1D.
  ❌ Tried (didn't work) Replacing the left rear wheel speed sensor., Clearing codes with a scan tool (they would return).
  ✅ What actually fixed it The owner took the truck to a dealer for a recall on the ABS module, and the issue has not returned since the recall was performed.