C0045 on 2008-2013 Cadillac CTS: Left Rear Wheel Speed Sensor Circuit Causes and Fixes

What's Unique About the 2008-2013 Cadillac CTS

For this generation of Cadillac CTS, the wheel speed sensor's target is not a traditional toothed 'tone ring'. Instead, it's a magnetic encoder ring integrated into the wheel hub/bearing assembly. This design is notoriously prone to failure; the magnetic material can crack, delaminate from thermal cycles, or accumulate metallic debris, causing an erratic or missing signal. As a result, the most common fix for a C0045 code is often replacing the entire wheel hub assembly, even if the wheel speed sensor itself is still functional. A widely referenced General Motors TSB (PIC5428 series) directly addresses this issue, recommending cleaning the ring as a first step before any parts are replaced.

Generation note: The 2008-2013 model years cover the second generation of the Cadillac CTS. The issues related to the magnetic encoder ring on the wheel hub are specific to this platform design and are also seen on platform-mates like the 2010-2015 Chevrolet Camaro.

Symptoms You May Notice

• ABS warning light illuminated
• StabiliTrak or Traction Control warning light illuminated
• "Service StabiliTrak" or "Service Traction Control" message on the driver information center (DIC)
• ABS and/or traction control systems are disabled
• Cruise control is inoperative
• A grinding, clicking, or ratchet noise from the rear wheel area at low speeds, which can be the ABS pump motor activating intermittently

Most Likely Causes

1. Damaged or Contaminated Rear Wheel Hub Magnetic Encoder Ring 🔴 High Probability The magnetic ring integrated into the hub is exposed and can become brittle, crack, or collect metallic 'fuzz' over time, which disrupts the sensor reading. This is a well-documented issue on this GM platform, covered by TSB PIC5428F.
   How to confirm: Visually inspect the magnetic ring on the inboard side of the left rear wheel hub. Look for cracks, missing pieces, or a build-up of metallic debris. A scan tool showing erratic or zero speed from the left rear wheel while others read normally points to this corner. A special magnetic encoder test card can also be used to verify the ring's integrity.
   Typical fix: First, attempt to clean the ring with a soft nylon brush and mild soap/detergent, per GM TSB PIC5428F. Do not use magnets for cleaning as they can damage the encoder. If cleaning fails or the ring is physically damaged, replace the entire left rear wheel hub and bearing assembly. The magnetic ring is not serviced separately.
   Est. part cost: $150-$350
2. Failed Left Rear Wheel Speed Sensor 🟡 Medium Probability → Shop ABS Wheel Speed Sensor The sensor is exposed to harsh conditions (water, heat, debris) which can lead to internal failure or corrosion at the connector. It is a common misdiagnosis for a bad hub encoder ring.
   How to confirm: Swap the left and right rear wheel speed sensors. If the code changes to C0050 (Right Rear), the sensor is bad. If the C0045 code remains, the problem is not the sensor. Alternatively, use a multimeter to check for proper resistance and a scope to check for a signal.
   Typical fix: Replace the left rear wheel speed sensor. It is typically held in by a single bolt.
   Est. part cost: $40-$90
3. Damaged Wiring or Connector ⚪ Low Probability The wiring harness runs near suspension components and can be subject to chafing, stretching, or corrosion, especially at the connector plug. The pins can also lose tension over time.
   How to confirm: Visually inspect the wiring harness from the sensor up into the wheel well for any signs of physical damage, chafing, or corrosion at the connector pins. A Corvette owner with the same code C0045 found the issue was a corroded connector near the battery, not the hub or sensor. Perform a continuity and resistance test on the wiring.
   Typical fix: Repair the damaged section of wiring or replace the pigtail connector. Clean corroded connectors with electronic cleaner and ensure a snug fit.
   Est. part cost: $20-$50

Rare But Worth Checking

• Faulty Electronic Brake Control Module (EBCM): → Shop ABS Control Module This is the least likely cause. Suspect the EBCM only after definitively ruling out the hub, sensor, and wiring. An EBCM failure will often set multiple wheel speed sensor codes simultaneously. GM has noted that the EBCM can be misdiagnosed as faulty when the issue lies elsewhere in the circuit.

Diagnosis Steps

1. Connect an OBD-II scanner capable of reading ABS codes to confirm C0045 is the active or stored code.
2. Use the scanner's live data function to monitor all four wheel speeds while driving slowly (above 5-10 mph). Confirm that the left rear wheel speed reads 0, is erratic, or significantly different from the other three.
🎬 Watch: How to troubleshoot and fix C0045 and C0050 codes.
3. Safely lift and support the vehicle. Remove the left rear wheel.
4. Visually inspect the wheel speed sensor and its wiring harness for any obvious damage, corrosion, or loose connections. Pay close attention to the connector plug and pins.
5. Carefully inspect the magnetic encoder ring on the inboard side of the wheel hub assembly. Look for any cracks, peeling, missing sections, or an accumulation of metallic debris ('fuzz').
6. Crucial First Step: If debris is found, clean it off thoroughly using a soft nylon bristle brush and a mild soap/detergent solution. Do NOT use a magnetic tool or harsh solvents. After cleaning, clear the codes and test drive to see if the code returns. If it does not, the problem is solved. If it does, the ring is likely damaged or another fault exists.
7. If the ring appears physically damaged (cracked, delaminated), the entire wheel hub assembly must be replaced.
8. If the ring looks intact and clean, test the sensor. The easiest method is to swap the left and right rear sensors. Clear codes and test drive. If the code changes to C0050, the sensor is faulty. If C0045 returns, the issue is the hub or wiring.
9. If the sensor and hub are confirmed good, perform continuity and resistance checks on the wiring harness between the sensor connector and the EBCM. Check for corrosion in any intermediate connectors.

Parts You'll Likely Need

• Rear Wheel Hub and Bearing Assembly (OEM #22889198) — This is the most common failure point for code C0045 on this vehicle, as the integrated magnetic encoder ring fails, not the separate sensor. The ring is not sold separately.
  Trusted brands: ACDelco (GM OE), Timken (e.g., 512372), MOOG (e.g., 513282), SKF
  OEM price range: $250-$350
  Aftermarket price range: $150-$250
• Rear Wheel Speed Sensor (OEM #20938121) — While less common than hub failure, the sensor itself can fail due to harsh environmental conditions. It's often replaced as a diagnostic step, sometimes incorrectly.
  Trusted brands: ACDelco (GM OE), Delphi, Standard Motor Products (SMP), Duralast (e.g., SU12032)
  OEM price range: $70-$100
  Aftermarket price range: $40-$70

Related Codes That Often Appear With This One

• C0050 — If both C0045 and C0050 (Right Rear Wheel Speed Sensor Circuit) are present, it could indicate a problem common to both rear wheels, such as a wiring harness issue or a failing EBCM. On the CTS and its platform mates, it's also common for both rear hubs to fail around the same time.
• U0415 — According to GM service information (PIC5428F), a loss of a wheel speed sensor signal is a known cause for this 'Invalid Data Received From Electronic Brake Control Module' code. This may also trigger a 'Service Steering' message and cause a heavier steering feel at low speeds.

Technical Service Bulletins (TSBs) & Recalls

• PIC5428F: EBCM Wheel Speed Sensor Diagnostic Aid for ABS Message -Click Or Ratchet Noise- Service Traction Message - Service Stabilitrak Message - Service Steering Message. This TSB confirms that debris on the magnetic encoder ring is a primary cause for C0045 and lists a wide range of affected GM vehicles, including the CTS, Camaro, SRX, and more.

Platform-Specific Known Issues

• General Motors issued multiple versions of Preliminary Information bulletin PIC5428 (with revisions A through F), specifically citing that DTCs like C0045 are often caused by metallic debris accumulating on the magnetic encoder ring of the hub bearing. The fix is often to clean the ring, but if it's damaged or cleaning doesn't resolve the issue, the hub must be replaced.

Mechanic-Grade Diagnostic Values

• Wheel Speed Sensor Signal (Oscilloscope) — expected: A clean square wave that increases in frequency as the wheel is spun. The voltage should toggle between approximately 7V (low) and 12V (high).. Failure: A missing, erratic, or 'noisy' square wave pattern indicates a problem with the sensor or the magnetic encoder ring.
• Wheel Speed Sensor Resistance — expected: Not applicable. These are active MR sensors, not passive variable reluctance (VR) sensors. They cannot be accurately tested for resistance with a standard multimeter.. Failure: Attempting to measure resistance is an invalid test and may lead to misdiagnosis. The sensor is powered by the EBCM.

Hidden / Shadow Codes Worth Checking

• C0045 0F: Left Rear Wheel Speed Sensor Circuit Erratic Signal. This symptom byte is highly indicative of debris on the magnetic encoder ring or a cracked/delaminating ring, as the sensor is still producing a signal, but it's inconsistent. (see via GM Tech2 or GDS2 scan tool, or high-end professional scanners with manufacturer-specific capabilities.)
• C0045 5A: Left Rear Wheel Speed Sensor Circuit Plausibility Failure. The EBCM sees a signal from this sensor that is illogical compared to the other wheel speed sensors (e.g., three wheels at 40 MPH, one at 2 MPH). (see via GM Tech2 or GDS2 scan tool, or high-end professional scanners.)
• C0045 00: Left Rear Wheel Speed Sensor Circuit Malfunction. This is a more general failure code indicating a loss of signal or other fault that doesn't fit the more specific symptom bytes. (see via GM Tech2 or GDS2 scan tool, or high-end professional scanners.)

Scan Tool Commands That Help

• GDS2 / Tech2: Module Diagnosis > EBCM > Data Display > Wheel Speed Sensor Data — This is the primary diagnostic step. Use this to watch the live data from all four sensors simultaneously while driving. A faulty left rear sensor/circuit will show a speed of 0, a fluctuating reading, or a speed that doesn't match the others.
• GDS2 / Tech2: Clear DTCs — After performing a repair (like cleaning the ring or replacing a part), this function must be used to clear the C0045 from the EBCM's memory. No special relearn or calibration is needed for a wheel speed sensor or hub replacement.

Wiring & Ground Locations

• G110 — On the left frame rail, below the driver's door area, near the EBCM.. This is a primary ground point for the Electronic Brake Control Module (EBCM). Corrosion or a loose connection at this point can cause erratic EBCM behavior and may lead to false wheel speed sensor codes, including C0045.
• EBCM Connector — On the EBCM, which is attached to the ABS hydraulic block in the engine compartment on the driver's side.. This is the termination point for the sensor circuit. Technicians can back-probe the pins for the left rear WSS (e.g., Pin 34 for Signal, Pin 35 for Low Reference, though pin numbers can vary by year) to check for a signal directly at the module, confirming if the wiring harness is intact.
• Rear Wheel Speed Sensor Harness — Runs from the sensor in the wheel hub, up the suspension control arm, and into the chassis through the wheel well.. This section of the harness is subject to constant movement and exposure to debris. It is a common point for chafing against the subframe or suspension components, leading to an open or shorted circuit.

Real Owner Repair Stories

• CadillacForums user report (2009 Cadillac CTS) — ABS and Stabilitrak lights on, code C0045.
  ❌ Tried (didn't work) Replaced the left rear wheel speed sensor., Replaced the left rear wheel hub assembly.
  ✅ What actually fixed it After the new parts didn't fix the issue, the owner traced the wiring harness from the wheel. They found a spot where the harness had rubbed through on the rear subframe, causing a short. Repairing the damaged wire permanently resolved the code.
• YouTube channel 'BeerWrench Garage' (2011 Chevrolet Camaro (platform mate)) — ABS and Traction Control lights on, codes C0045 and C0050.
  ❌ Tried (didn't work) Initial thought was to replace sensors.
  ✅ What actually fixed it The mechanic removed the rear wheel and sensor to inspect the magnetic encoder ring on the hub. It was covered in a thick layer of metallic 'fuzz'. He cleaned the ring thoroughly with a brush and brake cleaner, reassembled, and cleared the codes. A test drive confirmed the fix, with live data showing perfect signals from both rear wheels.
• CTSVowners.com user report (2011 Cadillac CTS-V) — Service Stabilitrak message, C0045 code.
  ❌ Tried (didn't work) Cleaning the magnetic ring (it looked clean but was faulty).
  ✅ What actually fixed it Upon close inspection, the magnetic encoder ring on the original hub had multiple hairline cracks. The cracks were not obvious until the hub was removed and examined closely. Replacing the entire wheel hub assembly with a new Timken unit solved the problem immediately.
• NHTSA ODI #11219167 (Cadillac SRX platform-mate) — An owner reported an ABS stability code C0045. The diagnosis revealed the left rear wheel speed sensor encoder ring was broken. The repair required replacing both the speed sensor and the rear hub assembly to resolve the fault.

OEM Part Supersession History

• 22889198 → 23485301, then 84433235 — Revisions to improve durability or consolidate parts.
  Heads up: While the core function is the same, always verify the correct part number for your specific vehicle's VIN and RPO codes (e.g., J55 performance brakes vs JL9 standard brakes), as caliper mounting points on the knuckle/hub assembly can differ.
• 20938121 → 23484247 — Part number consolidation or minor design revision.
  Heads up: The sensors are generally interchangeable across the generation, but using a VIN-matched part number is always the safest practice.

Diagnostic Flowchart

Used vs. New Parts: Buying Guide for This Vehicle

When a used part is the smart pick: A used wheel speed sensor or a wiring harness pigtail from a low-mileage donor car can be a cost-effective choice, as they are simple to swap if they don't work. A used EBCM is also a possibility but may require dealer programming.

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

What to inspect on the donor part:

• For a sensor, ensure the plastic housing is not cracked and the connector pins are clean and straight.
• For a wiring pigtail, inspect for any signs of brittleness, chafing, or previous repairs.
• Avoid parts from vehicles in regions with heavy road salt usage, as corrosion is a major concern.

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

• While not strictly 'OEM-only', it is strongly advised to avoid used or cheap, unbranded 'white box' wheel hub assemblies. The failure is a wear-and-tear item, and a used hub has unknown remaining life.

Aftermarket brands forum-validated for this vehicle:

• Hub Assemblies: Timken, SKF, MOOG, and ACDelco (OE) are consistently recommended on forums for their quality and durability.
• Sensors: Delphi, Standard Motor Products (SMP), and ACDelco (OE) are reliable choices.

Brands owners have reported issues with on this vehicle:

• No-name or 'white-box' wheel hub assemblies from online marketplaces like Amazon or eBay are frequently reported to fail prematurely, sometimes causing the C0045 code to return within a few months.

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 the direct counterpart to C0045. It may appear with C0045 if both rear hubs are failing, or it can be used diagnostically by swapping the left and right sensors to see if the code follows the sensor.
• C0035 — This code indicates a fault in the Left Front Wheel Speed Sensor Circuit. The underlying cause, a contaminated or damaged magnetic encoder ring on the hub, is a known issue on this GM platform and can occur on the front wheels as well.
• C0040 — This code indicates a fault in the Right Front Wheel Speed Sensor Circuit. Like C0035, it points to the same type of failure as C0045 but on a different wheel, and is covered by the same diagnostic principles outlined in TSB PIC5428F.
• U0121 — Lost Communication With Anti-Lock Brake System (ABS) Control Module. While less common, a fault in the wiring to the EBCM or an internal EBCM failure could prevent it from receiving any wheel speed data, potentially triggering a C0045 code as a secondary symptom.

Frequently Asked Questions