C0045 on 2018 GMC Sierra HD: Causes and Fixes for Left Rear Wheel Speed Sensor Circuit

What's Unique About the 2018-2018 GMC Sierra HD

For 2018 GM HD trucks, this code is common enough that GM issued a specific Technical Service Bulletin, #PIE0456A, to investigate its root cause. This was an 'Engineering Information' bulletin, meaning GM was actively gathering data from dealerships on vehicles with C0045 or the right-side equivalent C0050, confirming a known pattern of faults. The bulletin specifically directed technicians to inspect sensor terminals and harness connectors before repair, highlighting them as primary areas of concern. A common failure point is the wiring harness chafing on the axle housing or corrosion in the main chassis connector (X411) on the frame rail.

Symptoms You May Notice

• ABS warning light illuminated
• StabiliTrak or Service Traction Control warning light illuminated
• Service Trailer Brake message on the Driver Information Center
• ABS system is inoperative
• Cruise control may be disabled

Most Likely Causes

1. Damaged Wheel Speed Sensor Wiring or Connector 🔴 High Probability The wiring harness is notoriously prone to chafing against the axle housing or frame rail. Forum users frequently report finding a broken wire 6-12 inches from the sensor connector. The main chassis connector on the left frame rail, X411, is also a known spot for water intrusion and pin corrosion. TSB #PIE0456A specifically called for inspection of the harness and connectors.
   How to confirm: Visually inspect the entire length of the harness from the wheel to the main frame connector. Pay special attention to where it runs over the axle housing and is secured by clips. Disconnect and inspect the X411 connector on the frame rail for green or white corrosion. Tug gently on the wires at the sensor connector to check for internal breaks.
   Typical fix: Repair the broken wire(s) with solder and heat-shrink tubing or replace the harness pigtail connector. Ensure the harness is properly secured in all clips and consider adding protective conduit in chafe-prone areas.
   Est. part cost: $15-$45
2. Failed Left Rear Wheel Speed Sensor 🔴 High Probability The sensor is an electronic component exposed to harsh conditions (water, salt, vibration) at the wheel, leading to eventual failure. Another common issue is 'rust jacking,' where rust builds up under the sensor's mounting flange, increasing the air gap to the magnetic ring and causing a weak or lost signal.
   How to confirm: After confirming the wiring is intact, test the sensor. A professional scan tool can read live data to see if the sensor is reporting speed. With a multimeter, the sensor's resistance should be between 850-1350 ohms. 🎬 Watch how to test a speed sensor with a multimeter An AC voltage reading while spinning the wheel should be >100mV and increase with speed.
   Typical fix: Replace the left rear wheel speed sensor. It is held in by a single T30 Torx or 8mm bolt. It is critical to thoroughly clean the mounting surface on the hub of all rust and debris before installing the new sensor to ensure the correct air gap.
   Est. part cost: $30-$65
3. Damaged or Contaminated Wheel Hub Magnetic Encoder Ring ⚪ Low Probability The magnetic ring is integrated into the wheel hub assembly. It can become contaminated with metallic debris from a failing wheel bearing, or it can crack, disrupting the sensor's reading.
   How to confirm: With the sensor removed, visually inspect the magnetic ring inside the hub for cracks or a build-up of metallic 'fuzz'. Check for excessive play or noise from the wheel bearing by rocking the tire at the 12 and 6 o'clock positions.
   Typical fix: If the encoder ring is damaged or the bearing has failed, the entire wheel hub and bearing assembly must be replaced.
   Est. part cost: $150-$400

Rare But Worth Checking

• Faulty Electronic Brake Control Module (EBCM): This is very uncommon and should only be considered after all other possibilities have been definitively ruled out. An EBCM failure usually triggers multiple, often communication-related, codes. TSB #PIT5499B for the GMC Canyon does mention checking the EBCM connector for water intrusion as a possible cause for C0045, which is plausible on the Sierra HD as well.

Diagnosis Steps

1. Read the fault codes with an OBD-II scanner capable of accessing the ABS module.
2. Use the scanner's live data function to monitor the wheel speed of all four wheels while driving. Confirm that the left rear wheel speed reads 0 mph or is erratic compared to the others.
3. Lift the vehicle and perform a thorough visual inspection of the left rear wheel speed sensor and its wiring harness for any obvious signs of damage, chafing, or corrosion. Pay close attention to where the harness runs along the axle tube and up to the frame connector X411.
4. Disconnect the sensor and the main EBCM connector to inspect terminals for corrosion or damage. The EBCM is on the left frame rail.
5. If wiring appears intact, test the sensor's resistance with a multimeter. It should be 850-1350 ohms. Compare the reading to the right rear sensor.
6. Test for AC voltage output from the sensor while spinning the wheel. It should generate over 100mV.
7. If the sensor tests good, perform a continuity and short-to-ground test on the wiring harness between the sensor connector and the EBCM connector pins (Pin 34 Dark Green, Pin 35 Tan/White). Wiggle the harness during this test to find intermittent breaks.
8. If the sensor and wiring are confirmed to be good, remove the sensor and inspect the magnetic encoder ring on the wheel hub for damage or metallic debris.
9. If no other cause is found, the final possibility is a fault within the EBCM, though this is rare.

Parts You'll Likely Need

• Rear Wheel Speed Sensor (OEM #23299335) — This is the most common part to fail for this code, due to its exposure to the elements and issues like rust jacking. This part number fits both left and right rear positions on many GM trucks.
  Trusted brands: ACDelco (OEM), Delphi, Dorman, Standard Motor Products (SMP)
  OEM price range: $30-$60
  Aftermarket price range: $25-$50
• ABS Wheel Speed Sensor Connector (Pigtail) (OEM #PT2160) — If the connector at the sensor is corroded or the wires are broken right at the connector body, replacing the pigtail is the standard repair.
  Trusted brands: ACDelco, Dorman, Standard Motor Products
  OEM price range: $25-$40
  Aftermarket price range: $10-$25
• Rear Wheel Hub and Bearing Assembly — This is only needed if the integrated magnetic encoder ring is found to be damaged or if the wheel bearing itself has failed, contaminating the sensor area with metal debris.
  Trusted brands: ACDelco, Timken, MOOG, SKF
  OEM price range: $250-$400
  Aftermarket price range: $150-$300

Related Codes That Often Appear With This One

• C0050 — This is the code for the Right Rear Wheel Speed Sensor Circuit. It is mentioned alongside C0045 in TSB #PIE0456A. If both appear together, it strongly suggests a common wiring harness issue, like corrosion in the main X411 connector that serves both rear sensors.
• U0415 — This means 'Invalid Data Received From EBCM'. Other modules on the truck (like the TCM or PCM) set this code because they can no longer trust the data from the EBCM due to the C0045 fault.
• C0045-0F — This manufacturer-specific sub-code for 'Erratic Signal' points strongly to a damaged magnetic encoder ring or debris on the sensor tip. It requires a professional scan tool to read.

Technical Service Bulletins (TSBs) & Recalls

• PIE0456A: Service Stabilitrak, ABS, Service Trailer Brake Light, and/or Service Traction Control Indicator Illuminated with DTC C0045 or C0050 Set.
• PIT5499B: While for a different model (GMC Canyon), this TSB mentions C0045 in the context of water intrusion at the EBCM connector, which is a plausible, though rare, cause on the Sierra HD.
• PIT5427B: While for a different model (GMC Terrain), this TSB mentions C0045 in the context of a damaged X411 connector, a known issue on the Sierra HD as well.

Platform-Specific Known Issues

• GM issued Technical Service Bulletin #PIE0456A for 2018 Sierra HD models to gather engineering data on the root cause of C0045 and C0050. The bulletin directed technicians to inspect the sensor terminals and harness connectors before attempting repairs, which confirms that GM was aware of a high failure rate in the circuit, not just the sensor itself.

Mechanic-Grade Diagnostic Values

• Passive Wheel Speed Sensor Resistance — expected: 800-1700 Ohms at ambient temperature. Some sources state 850-1350 Ohms for GM specifically, while others give a wider range of 1200-2700 Ohms, which may account for temperature variations.. Failure: A reading of infinity (Open Loop) or zero ohms (short circuit). A reading outside the specified range suggests a failing sensor coil.
• Passive Wheel Speed Sensor AC Voltage Output — expected: Greater than 0.250 VAC (250mV AC) when spinning the wheel by hand at about half a revolution per second. Voltage should increase steadily with wheel speed.. Failure: No voltage or an erratic, jumpy voltage reading indicates a failed sensor or a problem with the magnetic encoder ring.

Hidden / Shadow Codes Worth Checking

• C0045-0F: Erratic Signal. This symptom byte points to a physically damaged or contaminated magnetic encoder ring, a loose sensor, or electrical interference, rather than a simple open/short in the circuit. (see via A professional scan tool like the GM GDS2 or an equivalent high-end scanner capable of reading manufacturer-specific symptom bytes.)
• C0045-5A: Signal Plausibility Failure. The EBCM is receiving a signal, but it's illogical compared to other vehicle sensors (e.g., other wheel speeds). This can be caused by a mismatched tire size or a failing sensor providing incorrect data. (see via A professional scan tool like the GM GDS2 or an equivalent high-end scanner.)
• C0045-00: No Signal / Circuit Malfunction. This is a general circuit fault that often indicates a completely dead sensor, a broken wire, or a disconnected plug. (see via A professional scan tool like the GM GDS2 or an equivalent high-end scanner.)
• C0045-06: Low Voltage / Open Circuit. This points specifically to a broken wire, a corroded/unplugged connector, or a short-to-ground in the sensor's wiring harness. (see via A professional scan tool like the GM GDS2 or an equivalent high-end scanner.)

Scan Tool Commands That Help

• GM GDS2 / High-End Scan Tool: Live Data - Wheel Speed Sensors — This is the first diagnostic step after reading the code. Monitor all four wheel speeds while driving to confirm the left rear sensor is the one reading incorrectly (e.g., stuck at 0 MPH or dropping out). This verifies the fault is active before any parts are replaced.
• GM GDS2 / High-End Scan Tool: Clear ABS DTCs — After a repair (like replacing a sensor or fixing a wire), this function is used to clear the C0045 code from the EBCM's memory. The warning lights should turn off, and the system will return to normal operation if the fix was successful.

Wiring & Ground Locations

• X411 — The main 16-pin chassis harness connector located on the left (driver's side) frame rail, generally above the rear axle.. This is the primary intermediate connector between the rear axle harness (which includes the left rear wheel speed sensor) and the main body harness that runs to the EBCM. It is a very common location for water intrusion and pin corrosion, which can cause an open or short in the sensor circuit, triggering C0045.
• G218 — A body ground point located under the dash, often behind the driver's side kick panel or under the carpet near the A-pillar.. This is a primary ground for the Body Control Module (BCM). While a poor ground here typically causes multiple, widespread electrical issues (as noted in TSB PIT5405C), a loose or corroded G218 could potentially create intermittent data communication errors (like U0415) that are seen alongside ABS faults. It's a less likely, but possible, contributing factor if other electrical gremlins are present.

Real Owner Repair Stories

• GM-Trucks.com forum user (2017 GMC Sierra 2500HD) — ABS and StabiliTrak warning lights on, code C0045 stored.
  ❌ Tried (didn't work) Replaced the left rear wheel speed sensor.
  ✅ What actually fixed it Found a chafed wire in the harness approximately 12 inches away from the sensor plug. The harness was rubbing against the axle housing. The wire was repaired and the harness was re-secured, which resolved the code.
• YouTube channel OldGuyDIY (2013 Chevrolet Impala (similar GM system)) — Persistent C0045 code with ABS and Traction Control lights.
  ❌ Tried (didn't work) Replacing the left rear hub assembly.
  ✅ What actually fixed it The owner discovered a broken orange wire in the wiring harness between the main under-car connector and the ABS sensor. The break was located near a plastic clip that attached the harness to the rear suspension. Splicing the wire fixed the issue.

OEM Part Supersession History

• 22775301, 23492815 → 23299335 — Standard part evolution, likely for improved durability, material, or manufacturing process.

Diagnostic Flowchart

Other Known Issues on This Vehicle

Issues unrelated to this code that are worth knowing about as an owner of this generation:

• 8-Speed & 6-Speed Transmission Shudder/Hard Shift 🔴 High — Very common issue, often appearing between 30,000-80,000 miles. Can manifest as a shudder at low, steady speeds or harsh shifts. (Ref: TSB #18-NA-355 (for fluid flush) and #16-NA-019 (for shift quality) were issued for related models.)
• DEF System Faults (Duramax) 🔴 High — Common on Duramax models, involving faulty DEF tank heaters, level sensors giving false readings (especially while towing), and NOx sensors. Parts are often on backorder. (Ref: Multiple bulletins exist, including updates for software to correct erratic DEF level reporting while towing (e.g., 24-NA-196).)
• Active Fuel Management (AFM) Lifter Failure (Gas V8s) 🔴 High — A known issue on the 5.3L and 6.2L gas engines where lifters can collapse or become stuck, causing misfires, engine noise, and potential engine damage. (Ref: TSB #15-06-01-002H addresses diagnosing lifter issues.)
• Infotainment System Black Screen/Failure 🟠 Medium — Owners report the main infotainment screen freezing, going black, or becoming unresponsive, sometimes requiring a full unit replacement.
• A/C Condenser Leaks 🟠 Medium — The A/C condenser is prone to developing leaks, leading to a loss of cooling performance. This is a frequent repair item for this generation.

Used vs. New Parts: Buying Guide for This Vehicle

When a used part is the smart pick: A used wiring harness pigtail from a junkyard can be a good option if the wires and connector are in excellent physical condition with no corrosion. For major components like the EBCM or wheel hub, a used part can be a cost-effective alternative to new OEM, but carries risks.

Donor-vehicle mileage cap: roughly under 80000 miles for the part to have meaningful remaining life.

What to inspect on the donor part:

• For wiring: Check for flexibility, no cracking insulation, and clean, corrosion-free connector pins.
• For a wheel hub: Spin the bearing by hand to ensure it is smooth with no noise or roughness. Visually inspect the magnetic encoder ring for any cracks, chips, or heavy rust.
• For an EBCM: Check for any physical damage to the housing or connectors. Ensure the donor vehicle did not have ABS-related codes.

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

• Electronic Brake Control Module (EBCM): While used OEM is an option, aftermarket or remanufactured modules can have high failure rates. A new or used OEM unit that is properly VIN-programmed is the most reliable choice.

Aftermarket brands forum-validated for this vehicle:

• ACDelco (Professional or GM Original Equipment)
• Delphi
• Timken (for wheel hubs)
• MOOG (for wheel hubs)

Brands owners have reported issues with on this vehicle:

• Avoid unbranded, 'white-box' electronic sensors and wheel hubs from online marketplaces, as they often have poor quality control and high failure rates.

Real Owner Stories

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

Related OBD-II Codes

• C0050 — This is the code for the Right Rear Wheel Speed Sensor circuit; it is frequently mentioned alongside C0045 in TSB #PIE0456A as both circuits share similar harness routing and connector vulnerabilities.

Frequently Asked Questions