C0050 on 2007-2014 GMC Sierra: Right Rear Wheel Speed Sensor Fault Causes and Fixes

What's Unique About the 2007-2014 GMC Sierra

On the 2007-2013 (GMT900) and 2014 (K2XX) GMC Sierra, the rear wheel speed sensor is a separate, bolt-on component, unlike some other GM vehicles where it's integrated into the wheel hub assembly. This often makes for a less expensive part replacement. However, the wiring harness that runs along the frame and axle is a known weak point, frequently suffering from corrosion, chafing, or broken wires near the sensor connector. Forum users and mechanics frequently report that the wires break internally, often within the first 6-12 inches of the sensor connector, with no visible damage to the insulation. This makes a simple visual inspection insufficient; a continuity or "wiggle" test is often 🎬 Watch: Diagnosing an intermittent C0050 code on a GM truck. required.

Generation note: This range covers two Sierra generations: the GMT900 (2007-2013) and the first year of the K2XX (2014). While the C0050 code has the same meaning for both, the specific routing of the wiring and part numbers may differ slightly. The diagnostic approach remains the same, with the wiring harness and sensor being the primary suspects on both platforms. The rear sensor for the 2014 (K2XX) model is a different design and part number than the 2007-2013 (GMT900) models.

Symptoms You May Notice

• ABS warning light is illuminated
• StabiliTrak or Traction Control warning light is illuminated
• "Service StabiliTrak", "Service Traction Control", or "Service Brake System" message on the driver information center.
• Brake warning light may be on
• Cruise control may be disabled
• A "Service Trailer Brake" message may appear on the Driver Information Center.

Most Likely Causes

1. Damaged or Corroded Wheel Speed Sensor Wiring/Connector 🔴 High Probability → Shop ABS Wheel Speed Sensor The harness is exposed under the truck and is susceptible to damage from road debris, moisture, and corrosion. Wires often break or corrode internally inside the insulation, right at the connector, or where the harness is clipped to the frame. This internal break is a very common point of failure on these trucks and is often missed during a simple visual check. Manufacturer service bulletins like TSB Bulletin #PIT5499B suggest that technicians should specifically inspect the Electronic Brake Control Module connector for water intrusion or corrosion when C0050 is present.
   How to confirm: Visually inspect the entire length of the wiring harness from the sensor to where it joins the main loom on the frame. Disconnect the harness and check for green corrosion on the pins. Use a multimeter on the ohms setting to check for continuity between the EBCM connector and the sensor connector. While monitoring continuity, wiggle the harness (especially near the connector) to expose any intermittent breaks. A reading of 'OL' or a very high resistance indicates an open circuit.
   Typical fix: Repair the broken/corroded section of wire or, more reliably, replace the pigtail connector. Use heat-shrink butt connectors for a weather-resistant repair.
   Est. part cost: $15-$40
2. Failed Right Rear Wheel Speed Sensor 🟡 Medium Probability → Shop ABS Wheel Speed Sensor The sensor is an electronic component exposed to harsh conditions (heat, vibration, moisture) and can fail internally over time. Some failures are heat-sensitive, occurring only after the vehicle has been driven for a while.
   How to confirm: After confirming the wiring is good, the sensor is the next likely culprit. On these active sensors, a resistance test can be misleading. The best test is with a scan tool to watch live data while driving; the RR sensor reading will be 0 or erratic. Alternatively, with the key on, back-probe the connector to check for the ~12V power supply from the EBCM. A diagnostic trick is to heat the sensor with a heat gun while monitoring the signal to see if it drops out, indicating a heat-related failure.
   Typical fix: Replace the right rear wheel speed sensor. It is typically held in by a single bolt. 🎬 See this walkthrough for replacing the rear wheel speed sensor. Be sure to thoroughly clean the mounting hole and surface of rust and debris before installing the new sensor.
   Est. part cost: $30-$70
3. Damaged Tone Ring / Magnetic Encoder ⚪ Low Probability The tone ring (or magnetic encoder) is integrated into the rear wheel bearing/hub assembly. While more protected than on other vehicles, it can still be damaged by debris, rust, or fail due to bearing failure, causing cracks or missing magnetic segments.
   How to confirm: With the sensor removed, use a light to visually inspect the tone ring through the sensor mounting hole while slowly rotating the wheel. Look for cracks, missing teeth, heavy rust buildup, or debris. Any damage to the ring requires replacement of the hub assembly.
   Typical fix: If the tone ring is damaged, the entire wheel hub/bearing assembly must be replaced.
   Est. part cost: $150-$400

Rare But Worth Checking

• Failed Electronic Brake Control Module (EBCM): → Shop ABS Control Module This is rare and should only be considered after all other possibilities (sensor, wiring, tone ring) have been definitively ruled out. An EBCM failure usually triggers multiple wheel speed sensor codes or communication errors, not just a single one. However, it's a known strategy for the EBCM to cut the 12V feed to a sensor circuit if it detects a fault, which can be misdiagnosed as a bad EBCM itself.
• Poor EBCM Ground Connection: A poor ground connection for the EBCM can cause a variety of intermittent ABS faults, including C0050. The main EBCM ground is located on the frame rail under the driver's side door. Corrosion at this point can cause high resistance, leading to unpredictable behavior from the module. Cleaning the frame to bare metal and ensuring a tight connection is a critical diagnostic step if other causes are ruled out.
• Connector X411 Damage: As noted in manufacturer TSB Bulletin #PIT5427B for similar GMC platforms, technicians should inspect the X411 connector for damage or corrosion, which can trigger a wide array of codes including C0050 and various communication (U-series) faults.

Diagnosis Steps

1. Connect an ABS-capable scan tool to verify code C0050 is active and check for any other related codes. Note any sub-codes like C0050-00 (general circuit malfunction) or C0050-5A (signal not plausible).
2. Use the scan tool to monitor live data for all four wheel speed sensors while driving in a straight line. The right rear sensor will likely read 0 mph or have an erratic signal compared to the others.
3. Note: On some GMT900 trucks, the rear sensors may not show a signal with the key on/engine off, and may require the vehicle to be running and in gear to produce a signal.
4. Raise and secure the rear of the vehicle. Remove the right rear wheel.
5. Perform a thorough visual inspection of the wheel speed sensor wiring harness. Look for chafing, melting, corrosion, or breaks, especially where the harness clips to the frame and axle.
6. Disconnect the sensor and inspect the connector terminals for corrosion or damage. A common failure point is an internal wire break within 6-12 inches of this connector.
7. With the key on, carefully check for a ~12V reference voltage at the harness-side connector. If it's missing, the EBCM may have disabled the circuit due to a detected fault, or there's a break further up the harness.
8. If wiring appears visually okay, perform a continuity test with a multimeter from the EBCM connector to the sensor connector. The right rear sensor wires are at pins 3 and 4 of the EBCM connector. Wiggle the harness during the test to find intermittent opens.
🎬 Watch: How to test the speed sensor and find wiring breaks.
9. If wiring is confirmed good, remove the single bolt (typically a T30 Torx or 10mm) holding the sensor and remove the sensor. It may be seized; gentle twisting and penetrating fluid can help.
10. Inspect the sensor for physical damage and the tone ring inside the mounting hole for debris or cracks. Clean the mounting bore thoroughly before installing a new sensor.
11. If the wiring and tone ring are intact, the sensor itself is the most likely cause of the failure.

Parts You'll Likely Need

• Rear Wheel Speed Sensor (OEM #20938122) — This is the most common part to fail after the wiring. The left and right rear sensors are often the same part. Always verify the part number with your vehicle's VIN. This part number is widely cross-referenced and supersedes 15121067 and 20763147.
  Trusted brands: ACDelco (GM Original Equipment), Delphi, Standard Motor Products (ALS1464), Dorman
  OEM price range: $50-$80
  Aftermarket price range: $30-$60
• Rear Wheel Speed Sensor Connector Pigtail (OEM #ACDelco PT2160) — If the wiring is corroded or broken at the connector, replacing the pigtail is the most reliable repair. This is a very common failure point.
  Trusted brands: ACDelco, Dorman (645-157, 645-134), Standard Motor Products (S-824)
  OEM price range: $25-$40
  Aftermarket price range: $15-$30

Related Codes That Often Appear With This One

• C0045 — This is the code for the Left Rear Wheel Speed Sensor Circuit. Seeing both C0045 and C0050 could point to a wiring issue common to both rear sensors (like damage where the harness splits) or a problem with the EBCM.
• U0415 — This code indicates 'Invalid Data Received From Electronic Brake Control Module'. It often appears in other modules (like the PCM or BCM) when the EBCM sets a fault like C0050 and stops broadcasting valid data on the CAN bus.

Technical Service Bulletins (TSBs) & Recalls

• While no TSB is specific to C0050 on the Sierra, TSB 16-NA-090 for other GM vehicles describes a similar condition where mis-routing or twisting of the front wheel speed sensor harness causes internal wire damage, leading to various ABS codes. This supports the common finding of wiring harness failure as a root cause on the Sierra.
• TSB 08-05-25-005 addresses intermittent 'Service StabiliTrak' messages on other GM platforms caused by a software anomaly in the EBCM, correctable by reprogramming. While less likely for a specific C0050 code, it's a known issue within the system.
• TSB Bulletin #PIT5499B notes that for vehicles displaying a "Service Trailer Brake" message alongside code C0050, technicians should inspect the Electronic Brake Control Module connector for water intrusion or corrosion.
• TSB Bulletin #PIT5427B identifies that code C0050, along with other chassis and communication codes, may be stored if there is damage or corrosion at the X411 connector.

Platform-Specific Known Issues

• Internal Wire Break at Harness Connector: A very common failure is for one of the wires to break inside the insulation, within a few inches of the sensor connector. A visual inspection will not reveal the fault. A continuity test while wiggling the wire is required to diagnose. This is documented in numerous owner forums and mechanic videos.
• Heat-Sensitive Sensor Failure: Some owners report the ABS/StabiliTrak lights only come on after the truck has warmed up. This can indicate a sensor that is failing internally when it reaches a certain temperature. A technician confirmed this by using a heat gun on the sensor while monitoring its signal on a scan tool, causing the signal to drop to zero.
• Rear Sensor Signal Requires Vehicle to be Running and In-Gear: A key diagnostic quirk on these GMT900 trucks is that the rear wheel speed sensors will not produce a signal on a scan tool with the key on and engine off, even if the wheel is spun by hand. The vehicle must be started and put into Drive or Reverse for the EBCM to process and display the rear wheel speeds. This can confuse technicians who expect to see a signal by simply spinning the wheel on a lift.

Mechanic-Grade Diagnostic Values

• Sensor Circuit Continuity — expected: < 2 ohms. Failure: High resistance or 'OL' (Open Loop) indicates a broken wire. A reading of several thousand ohms or megaohms points to corrosion in the circuit.
• Sensor Power Supply Voltage — expected: ~12V. Failure: 0V at the sensor connector (harness side) indicates either a break in the power wire from the EBCM or that the EBCM has internally shut down the circuit due to a detected short or open.
• EBCM Ground Resistance — expected: < 1 ohm. Failure: High resistance on the ground circuit can cause intermittent and unpredictable EBCM behavior, including false sensor codes.

Hidden / Shadow Codes Worth Checking

• C0050 0F: Indicates the EBCM has detected an erratic signal from the wheel speed sensor. This often points to a wiring/connector issue, a failing sensor, or debris on the tone ring. (see via Requires a professional scan tool (like the GM GDS2/Tech2) capable of reading GM-specific symptom bytes.)
• C0050 18: Indicates the signal amplitude from the sensor is too low. This is commonly caused by an excessive air gap between the sensor and tone ring, metallic debris on the ring, or a failing sensor. (see via Requires a professional scan tool (like the GM GDS2/Tech2) capable of reading GM-specific symptom bytes.)
• C0050 5A: Indicates the signal is 'not plausible'. The EBCM is receiving data that doesn't make sense compared to the other wheels, often caused by a damaged or cracked tone ring. (see via Requires a professional scan tool (like the GM GDS2/Tech2) capable of reading GM-specific symptom bytes.)
• C0050 06: Indicates the circuit has low voltage or is open. This points directly to a broken wire or severe corrosion in the harness. (see via Requires a professional scan tool (like the GM GDS2/Tech2) capable of reading GM-specific symptom bytes.)

Wiring & Ground Locations

• EBCM Connector Pins 3 & 4 — At the main electrical connector on the Electronic Brake Control Module (EBCM), located on the driver's side frame rail.. These are the specific pins for the Right Rear Wheel Speed Sensor circuit. Pin 3 (Green/Yellow wire) is the 12V power supply from the module, and Pin 4 (Violet wire) is the signal return. Testing for continuity and voltage should be done at these pins to isolate faults between the sensor and the module.
• G110 (EBCM Ground) — On the outside of the frame rail, located beneath the driver's side door. It is identifiable as a heavy (approx. 12-gauge) black wire.. This is the primary ground for the Electronic Brake Control Module. A poor connection here due to rust or looseness can cause intermittent ABS/Stabilitrak faults, including C0050 and communication codes like U1041. A GM TSB addresses cleaning this ground to prevent unnecessary EBCM replacement.

Real Owner Repair Stories

• YouTube channel "ScannerDanner" (2017 GMC Sierra with 57,900 km) — ABS light on, Stabilitrak message, active code C0050.
  ❌ Tried (didn't work) Visual inspection of the harness showed no obvious damage.
  ✅ What actually fixed it A continuity test from the EBCM connector (pins 3 & 4) to the sensor connector showed a completely open circuit. Further inspection revealed a tiny, almost invisible pinhole in the wire insulation near the sensor connector, which had allowed moisture to enter and corrode the wire internally. Splicing in a new section of wire and sealing the repair fixed the problem. The original sensor was not faulty.
• YouTube channel "Terence The DIY Guy" (2007 GMC Sierra 1500 4x4) — ABS light comes on randomly, code C0050 stored in history.
  ❌ Tried (didn't work) Initial scan tool check on a lift by spinning wheels showed no signal from rear sensors, which was confusing.
  ✅ What actually fixed it The technician discovered the truck must be running and in gear for the rear sensors to report speed. With the truck running on the hoist, he used a heat gun on the right rear sensor. The sensor's signal on the scan tool dropped to zero when heated, confirming a heat-sensitive internal failure. Replacing the sensor fixed the issue.
• Mitchell1 SureTrack Community Fix (2014 Chevrolet Tahoe LTZ 5.3L) — ABS light on, code C0050.
  ❌ Tried (didn't work) Visual inspection of wiring and connector found no faults., Replacing and programming a new EBCM restored the 12V supply but the code remained.
  ✅ What actually fixed it A dual failure occurred. First, testing showed the 12V supply from the EBCM to the sensor was missing, requiring EBCM replacement. After replacing the module, the 12V returned, but a lab scope showed the sensor itself was producing an erratic signal with dropouts. Replacing the right rear wheel speed sensor *after* replacing the EBCM finally cleared the fault.

OEM Part Supersession History

• 15121067 → 20763147, then 20938122 — Standard part evolution for improved durability or manufacturing process.
  Heads up: The current part number, 20938122, is the correct service replacement for the entire 2007-2013 GMT900 generation.

Model Year Variations Within This Range

• 2014 only: The 2014 GMC Sierra (K2XX platform) uses a different rear wheel speed sensor and harness connector design compared to the 2007-2013 models (GMT900 platform). While the code's meaning is the same, the parts are not interchangeable. The removal and installation procedure also differs slightly due to different harness routing clips and bolt torque specifications.

Diagnostic Flowchart

Used vs. New Parts: Buying Guide for This Vehicle

When a used part is the smart pick: A used wiring harness pigtail or a section of the rear harness from a junkyard can be a cost-effective solution if your issue is confirmed to be wiring damage and you can find a donor vehicle with a clean, corrosion-free harness. This is often better than multiple splices in a damaged wire.

Donor-vehicle mileage cap: roughly under 100000 miles for the part to have meaningful remaining life.

What to inspect on the donor part:

• For a harness: Inspect the connector for any signs of green or white corrosion on the pins.
• Check the wire insulation for at least 12 inches back from the connector; it should be flexible, not brittle or cracked.
• Avoid harnesses from vehicles in heavy salt-belt regions if possible.
• Wiggle the wires near the connector to feel for internal breaks.

OEM-only on this vehicle (don't cheap out):

• Electronic Brake Control Module (EBCM). Due to the need for VIN-specific programming and the high cost of a misdiagnosis, using a new or professionally remanufactured OEM module is strongly advised over a used one.

Aftermarket brands forum-validated for this vehicle:

• ACDelco (GM Original Equipment or Gold line)
• Delphi
• Standard Motor Products (SMP)
• NTK

Brands owners have reported issues with on this vehicle:

• No-name, unbranded sensors from online marketplaces have a higher reported failure rate. While some may work, the risk of premature failure or incorrect signal output often makes them a poor value.

Real Owner Stories

Aggregated from forums and TSBs cited above. Mileages and costs reflect what owners reported in those sources.

Related OBD-II Codes

• C0045 — This code is for the Left Rear Wheel Speed Sensor. It shares the exact same failure modes as C0050 (wiring harness damage, sensor failure) and is processed by the same EBCM, making it a common companion code if corrosion or damage is widespread.
• C0035 — This code is for the Left Front Wheel Speed Sensor. A fault here can trigger the same ABS and StabiliTrak warnings as C0050. TSB 16-NA-090 specifically mentions front harness issues, indicating a shared potential root cause.
• C0040 — This code is for the Right Front Wheel Speed Sensor. Like the other wheel speed sensor codes, it points to a fault in the same system and can be caused by the same types of wiring or sensor failures.
• C0050-00 — This is a specific sub-code of C0050, indicating a 'general circuit malfunction'. It points directly to an electrical issue like an open or short in the wiring, which is the most common cause on these trucks.
• C0050-5A — This is a specific sub-code of C0050, indicating the sensor's signal is 'not plausible'. This could be caused by an erratic signal from a failing sensor or a damaged tone ring.
• U0121 — This code indicates 'Lost Communication With Anti-Lock Brake System (ABS) Control Module'. If this code is present with C0050, it suggests a more serious problem with the EBCM itself or its main power/ground connections, rather than just the sensor circuit.

Frequently Asked Questions