C0031 on 2015-2016 Ram 1500: Left Front Wheel Speed Sensor Fault Causes and Fixes

What's Unique About the 2015-2016 Ram 1500

The 2015-2016 Ram 1500, part of the fourth generation (DS), uses a wheel speed sensor design where the sensor is mounted to the steering knuckle and reads a tone ring on the wheel hub assembly. The wiring harness is routed along the brake lines and suspension components, making it susceptible to damage from road debris, chafing from suspension movement, or corrosion. While the sensor itself is a common failure point, owners and technicians frequently report finding damaged wiring as the root cause on these trucks. A common failure point is where the harness runs near the frame rail and can rub through, causing an open or short circuit that can be difficult to spot without a thorough inspection.

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 is on
• Traction Control/Electronic Stability Control (ESC) warning light is on
• Cruise control is disabled.
• A 'Service 4WD' light may appear on 4x4 models.
• Brake pedal may pulse or feel like ABS is activating at low speeds before the warning lights become constant.

Most Likely Causes

1. Faulty Left Front Wheel Speed Sensor 🔴 High Probability The sensor is exposed to heat, moisture, and road debris, leading to internal failure over time. It's a common wear-and-tear item on many vehicles, including Ram trucks. Water intrusion and oxidation are known failure modes.
   How to confirm: Use a scan tool to monitor live data from all four wheel speed sensors while driving. The left front sensor will show an erratic, inconsistent, or zero mph reading compared to the others. A multimeter can be used to check for resistance across the sensor's two pins; a reading between 800 and 2,500 Ohms is generally expected, while an open (OL) or shorted (near 0 Ohms) reading indicates a bad sensor. A quick test can be done by waving a magnet in front of a removed sensor while monitoring the live data or using an oscilloscope; a good sensor will produce a signal.
   Typical fix: Replace the left front wheel speed sensor. The sensor is typically held in by a single Allen or hex bolt, but the brake caliper and rotor must be removed for access. 🎬 Watch this step-by-step guide to replacing the front ABS sensor. The sensor can become seized in the knuckle and may break upon removal, requiring extra time to extract the broken piece.
   Est. part cost: $70-$200
2. Damaged Wiring or Connector 🔴 High Probability The sensor harness is routed near moving suspension parts and is exposed to the elements. Wires can get stretched, chafed, or broken internally, and the connector pins can corrode. A particularly common spot for failure is where the harness runs along the frame and can rub, causing an intermittent or permanent open/short.
   How to confirm: Visually inspect the entire length of the wiring harness from the sensor to where it enters the main loom in the engine bay. Check for breaks, chafing, and corrosion. Test for continuity and check for shorts to ground/power on both wires between the sensor connector and the ABS module connector with a multimeter. Wiggling the harness while testing can reveal intermittent breaks.
   Typical fix: Repair the broken or shorted section of wire using solder and heat-shrink tubing. If the connector is damaged, replace it with a new pigtail connector (e.g., Standard Motor Products S-1895).
   Est. part cost: $15-$50 for a pigtail connector
3. Damaged or Contaminated Tone Ring ⚪ Low Probability The tone ring (or magnetic encoder) is part of the wheel hub assembly. While durable, severe corrosion can cause it to swell or break, and a failing wheel bearing can cause excessive runout, leading to a bad signal. This was a more common issue on older models but can still occur.
   How to confirm: After removing the wheel speed sensor, visually inspect the tone ring through the sensor mounting hole. Look for broken teeth, heavy rust scale, or metallic debris stuck to it. Check for any play in the wheel bearing.
   Typical fix: The tone ring is integrated into the wheel hub bearing assembly. If it is damaged, the entire front wheel hub assembly must be replaced.
   Est. part cost: $150-$350 for a hub assembly

Rare But Worth Checking

• Faulty ABS Control Module: This is rare and should only be considered after the sensor, wiring, and tone ring have been definitively ruled out. An ABS module failure would typically involve more codes than just C0031, often including communication codes. Some owners have had to send their modules for repair when a replacement was unavailable.

Diagnosis Steps

1. Connect an OBD-II scanner capable of reading ABS codes to confirm C0031 is active and note any sub-codes (e.g., -1D, -2F, -62).
🎬 Watch: Diagnosing the C0031-1D code on a Ram 1500.
2. View live data from all four wheel speed sensors. Drive the vehicle slowly (or spin the wheel by hand) and confirm the left front sensor reading is absent, erratic, or doesn't change compared to the others.
3. Raise and secure the vehicle. Visually inspect the left front wheel speed sensor and its wiring harness for any obvious signs of damage, such as breaks, chafing against suspension components, or corrosion at the connector. Pay close attention to the harness routing along the frame.
4. Unplug the sensor and inspect the connector pins for corrosion or damage. The connector has a red locking tab that must be disengaged.
5. If the wiring looks good, remove the brake caliper and rotor to access the sensor. Remove the sensor (typically one 5mm Allen bolt) and inspect the magnetic tip for metal debris. Also, inspect the tone ring inside the hub for damage or heavy rust.
6. If no visual faults are found, use a multimeter to test the wiring harness. Check for continuity on both wires from the sensor connector to the ABS module connector. The left front wheel speed sensor wires are at pins 8 and 9 of the ABS module connector. Then check each wire for a short to ground and a short to power.
7. If the wiring tests good, test the sensor itself. Check its internal resistance with a multimeter; a good sensor should read between 800-2500 Ohms. Alternatively, use the magnet trick while observing live data to confirm it can produce a signal.
8. If the sensor and wiring test good, the issue likely lies with the wheel hub/tone ring or, in rare cases, the ABS module itself.

Parts You'll Likely Need

• Front Wheel Speed Sensor (OEM #68292050AH) — This is the most common failure point for code C0031. The sensor is a sensitive electronic component that fails from heat cycles and exposure to the elements. This part number has been superseded multiple times (from 68292050AA, AB, AC, etc.), indicating revisions by the manufacturer.
  Trusted brands: Mopar, NTK, Dorman, Standard Motor Products (SMP)
  OEM price range: $150-$200
  Aftermarket price range: $70-$120.
• Front ABS Wheel Speed Sensor Connector Pigtail (OEM #68064999AA (Verify with dealer)) — If the wiring is damaged at the connector, or the connector itself is corroded or broken, a replacement pigtail is needed to splice into the harness.
  Trusted brands: Mopar, Standard Motor Products (S-1895), Dorman, ACDelco (PT2160)
  OEM price range: $30-$50
  Aftermarket price range: $15-$40.

Related Codes That Often Appear With This One

• C0034 — This code is for the Right Front Wheel Speed Sensor. Seeing both C0031 and C0034 together could point to a wiring issue common to both sides, different tire sizes front-to-rear, or a problem with the ABS module.
• U1409 — This is a network code indicating an implausible left front wheel speed signal was received. It often appears alongside C0031 as a secondary confirmation of the fault.
• C0031-62 — Signal Compare Failure. This specific sub-code means the ABS module sees a signal from the left front sensor, but it doesn't plausibly compare with the signals from the other three wheels. This can be caused by a faulty sensor, a damaged tone ring, or even a significantly different sized tire on one corner.

Technical Service Bulletins (TSBs) & Recalls

• 68292756A$ - Lists possible wheel speed sensor faults including C0031-1D, C0031-2F, and C0031-62.
• 68193650A$ - Also lists possible wheel speed sensor faults including C0031-1D, C0031-2F, and C0031-62.
• 05-001-20 - While for Jeep models, this TSB details the causes for various C0031 sub-codes (like -1D, -2F, -62) as being related to oxidation or water intrusion, and recommends sensor replacement. This provides context for similar failures on the related Ram platform.

Platform-Specific Known Issues

• The provided NHTSA Technical Service Bulletins (TSBs) #68292756A$ and #68193650A$ list C0031 with various suffixes (-1D, -2F, -62), confirming that specific electrical failure modes are tracked by the ABS module. These sub-codes are essential for an accurate diagnosis and are typically only visible with a dealer-level scan tool or advanced aftermarket tools like AlfaOBD.

Mechanic-Grade Diagnostic Values

• Passive Wheel Speed Sensor Resistance — expected: 800 - 2,500 Ohms (Ω). Failure: A reading of 0 Ω indicates a short circuit; an infinite reading (OL) indicates an open circuit.
• Active Wheel Speed Sensor Signal (Oscilloscope) — expected: A clean square wave that switches between a low voltage (approx. 0.5V) and a high voltage (approx. 1.1V) as the wheel is spun.. Failure: No signal, a noisy signal, or a signal that does not switch indicates a faulty sensor or tone ring.
• Continuity Test from Sensor Connector to ABS Module — expected: < 1.0 Ohm (Ω) on each wire. Failure: A high resistance or OL reading indicates a broken wire in the harness.

Scan Tool Commands That Help

• wiTECH or advanced aftermarket (e.g., AlfaOBD): ABS Initialization — Required after replacing the ABS control module to configure it to the vehicle.
• wiTECH or advanced aftermarket (e.g., AlfaOBD): ABS Bleed Procedure — Required after replacing the ABS hydraulic unit (pump) to cycle the internal valves and purge all air from the system. This is performed after a traditional manual bleed.

Wiring & Ground Locations

• ABS Control Module — Under the hood on the driver's side, located below the main fuse box (TIPM) and battery.. This is the destination for the wheel speed sensor signal. The main connector here is the endpoint for harness continuity tests.
• ABS Module Connector Pins (Left Front WSS) — Pins 8 and 9 on the main ABS module electrical connector.. These are the specific terminals for the Left Front Wheel Speed Sensor circuit. Probing here allows a technician to test the entire harness from the module to the sensor.
• ABS System Fuses — In the under-hood fuse box (Power Distribution Center): F6 (40A ABS Pump), F26 (30A ABS Valves), and F76 (10A ABS/ESC).. While a blown fuse is unlikely to cause a single sensor code, checking these fuses is a fundamental step in diagnosing a completely unresponsive ABS system.

Real Owner Repair Stories

• YouTube channel 'La Relic Hunter & Gulf South Detectors' (2015 Ram 1500) — ABS light, traction control light, cruise control disabled, code C0031-1D.
  ❌ Tried (didn't work) Initial diagnosis pointed to sensor or wiring.
  ✅ What actually fixed it The problem was resolved by replacing the left front wheel speed sensor.
• YouTube channel 'Pine Hollow Auto Diagnostics' (2021 Ram 1500 (newer but highly relevant diagnosis)) — ABS light returned one day after a shop replaced the front left wheel hub. Code C0031-1D was active.
  ❌ Tried (didn't work) Replacing the wheel hub assembly (which includes the sensor) did not fix the issue long-term.
  ✅ What actually fixed it A continuity test from the ABS module to the sensor connector revealed high resistance. The technician found a broken wire within the harness, repaired the wire, and resolved the code. This proved the new part was not defective.

OEM Part Supersession History

• 68292050AA, AB, AC, AD, AE, AF, AG → 68292050AH — Manufacturer revisions to improve reliability or sourcing.
  Heads up: The latest part number (AH) is the correct service replacement for all previous versions.