C0045 on 2007-2014 Chevrolet Tahoe: Left Rear Wheel Speed Sensor Circuit Fixes

What's Unique About the 2007-2014 Chevrolet Tahoe

For the 2007-2014 (GMT900) Tahoe, the rear wheel speed sensors are separate components that can be replaced individually, unlike the front sensors which are integrated into the more expensive wheel hub assemblies. This makes fixing a rear-specific code like C0045 much more affordable. While no TSBs are specific to the Tahoe for this code, related GM truck bulletins point to wiring harnesses being a common failure point, often due to improper routing, chafing, or damage during other suspension or axle repairs.

Symptoms You May Notice

• ABS warning light is on
• StabiliTrak or Traction Control warning light is on
• "Service StabiliTrak" or "Service Traction Control" message on the driver information center
• Cruise control is disabled or will not engage.
• In some cases, owners report harsh or erratic transmission shifting as the vehicle's computer loses a key speed input.
• A grinding or clicking noise from the ABS pump on startup as it performs its self-test and detects the fault.

Most Likely Causes

1. Failed Left Rear Wheel Speed Sensor 🔴 High Probability → Shop ABS Wheel Speed Sensor The sensor is exposed to harsh conditions (water, dirt, heat, vibration) at the wheel, leading to internal failure over time. Many owners on forums report that cheaper aftermarket sensors fail quickly and strongly recommend using genuine GM/ACDelco parts.
   How to confirm: Use a scan tool to monitor live data from all four wheel speed sensors while driving. If the left rear sensor reads 0 MPH or has an erratic signal while the others read correctly, the sensor is likely bad. 🎬 See how to test a wheel speed sensor using a multimeter. Another method is to swap the left and right rear sensors; if the code changes to C0050 (right rear), the sensor is confirmed bad. You can also test the sensor's internal resistance with a multimeter and compare it to the right side sensor; the readings should be very close.
   Typical fix: Replace the left rear wheel speed sensor. It is held in by a single T30 Torx bolt which can be very tight due to thread locker and corrosion. Applying heat to the surrounding axle housing or using an impact driver may be necessary. The same part is used for the left and right rear wheels.
   Est. part cost: $25-$85
2. Damaged Wiring Harness or Connector 🟡 Medium Probability The wiring harness leading to the sensor can be damaged by road debris, chafing against suspension components (especially near the upper shock mount), or corrosion at the connector pins. The harness can also be stretched or damaged during other repairs like shock replacement or differential work.
   How to confirm: Visually inspect the entire length of the wiring from the sensor to where it joins the main harness on the frame rail. Pay close attention to the area above the top bolt of the shock absorber. Disconnect the sensor and the main harness connector and check for breaks, chafing, or green/white corrosion inside the connector plugs. Check for continuity on both wires using a multimeter.
   Typical fix: Repair the damaged section of wire with solder and heat-shrink tubing or replace the pigtail connector if the terminals are corroded or broken. Ensure the harness is properly routed and secured away from moving parts.
   Est. part cost: $15-$40 for a pigtail connector
3. Debris on or Damage to the Tone Ring ⚪ Low Probability The sensor reads a toothed 'tone ring' (or reluctor ring) inside the axle housing. Metallic brake dust and rust can accumulate on the ring, disrupting the sensor's magnetic signal.
   How to confirm: After removing the wheel speed sensor, use a light to look inside the mounting hole. Rotate the axle and inspect the tone ring for heavy rust, debris, or broken teeth.
   Typical fix: Clean the tone ring with a Q-tip and brake cleaner or alcohol. If the ring is physically broken or warped (which is rare on this platform), the axle shaft must be removed for ring replacement.
   Est. part cost: $0 for cleaning, significant labor if the ring needs replacement

Rare But Worth Checking

• Faulty Electronic Brake Control Module (EBCM): → Shop ABS Control Module This is an uncommon cause. An EBCM failure typically triggers multiple wheel speed sensor codes, communication codes, or internal fault codes simultaneously, not just a single one like C0045.

Diagnosis Steps

1. Connect an OBD-II scanner capable of reading ABS/Chassis codes to confirm C0045 is the active or stored code.
2. Use the scanner's live data function to view the wheel speed from all four sensors while driving slowly (5-10 MPH). Confirm that the Left Rear (LR) sensor shows 0 MPH or an erratic reading compared to the others.
3. Raise and safely support the rear of the vehicle.
4. Visually inspect the wheel speed sensor wiring harness from the sensor itself, along the axle tube, and up to the main connector on the frame rail. Pay special attention to the area above the upper shock mount, a known chafe point. Look for any signs of chafing, melting, or physical damage.
5. Disconnect the sensor and inspect the connector pins for corrosion, moisture, or damage. If a multimeter is available, check for continuity through the harness.
6. If the wiring looks good, remove the single T30 Torx bolt holding the sensor in place. The bolt may be very tight and require an impact tool or heat to break loose.
7. Remove the sensor. Inspect the tip for damage or heavy metallic debris.
8. Look inside the sensor mounting hole with a flashlight and inspect the tone ring for debris or damage. Clean it with a Q-tip and brake cleaner if necessary.
9. Diagnostic Swap: If the wiring and tone ring are good, swap the left and right rear sensors. They are identical. Clear the codes and test drive. If the code changes to C0050 (Right Rear Wheel Speed Sensor Circuit), the original sensor is faulty.
10. Resistance Test: Alternatively, with the sensor unplugged, use a multimeter set to Ohms to measure the resistance across the two pins on the sensor. Compare this reading to the sensor on the right side. If the readings are vastly different (e.g., one is open-loop 'OL' and the other has a reading), the sensor is bad.
11. Install a new sensor (preferably an OEM ACDelco part), ensuring it is fully seated.
12. Clear the code with the scan tool and perform a test drive to ensure the warning lights do not return.

Parts You'll Likely Need

• Rear Wheel Speed Sensor (OEM #20938122) — This is the most common part to fail for this code after wiring issues have been ruled out. It is an accessible, standalone part on the rear of this vehicle. Owner experiences strongly suggest OEM is more reliable than aftermarket.
  Trusted brands: ACDelco (GM Genuine), Dorman, NTK, Standard Motor Products (SMP)
  OEM price range: $50-$85
  Aftermarket price range: $25-$50

Technical Service Bulletins (TSBs) & Recalls

• PIT4648D: While for Express/Savana vans, this GM bulletin highlights a known issue pattern where mis-routed wheel speed sensor harnesses can pull wires from the connector during suspension travel, causing C0045/C0050 codes. This is relevant as it shows a known failure pattern on similar GM truck platforms.
• General TSBs like #21-NA-149 and #10-00-89-005 discuss common wiring harness chafe points and proper repair procedures on various GM trucks, which are relevant to the likely cause of this code.

Platform-Specific Known Issues

• Wiring Chafe Point: A commonly reported issue is the sensor harness chafing on the frame right above the upper shock mount. When replacing shocks or doing other work, the harness can be disturbed or improperly re-secured, leading to this code.
• Aftermarket Sensor Quality: Multiple owner forums contain stories of users replacing the sensor 2-3 times with aftermarket brands (Dorman, Duralast) that were either dead-on-arrival or failed within days, with the issue only being resolved by installing a genuine ACDelco sensor.
• Stuck Torx Bolt: The T30 Torx bolt holding the sensor is notorious for seizing. Owners report needing to use penetrating oil, heat on the axle housing (not the sensor), and sometimes hammering on the head of the bolt to shock it loose before it can be removed without stripping.

Mechanic-Grade Diagnostic Values

• Passive Wheel Speed Sensor Resistance — expected: 850 - 1350 Ohms across the two sensor pins.. Failure: A reading of infinite resistance (OL) indicates an open circuit. A reading near zero indicates a shorted sensor.
• Passive Wheel Speed Sensor AC Voltage Output — expected: Greater than 100mV AC when spinning the wheel by hand, increasing with speed.. Failure: A reading of 0V AC or an erratic voltage that doesn't correspond to wheel speed points to a failed sensor or a damaged tone ring.
• EBCM Key-On Circuit Check (for active sensors) — expected: A brief 12-volt pulse from the EBCM to the sensor connector immediately upon turning the ignition key to 'ON'.. Failure: Absence of this pulse suggests a problem with the EBCM or the wiring between the module and the sensor. This test is best captured with an oscilloscope. The EBCM will often cut power to the circuit once a fault is stored, making this initial pulse a key diagnostic clue.

Hidden / Shadow Codes Worth Checking

• C0045 00: No Signal / Circuit Malfunction. Indicates a dead sensor, a complete wire break, or a disconnected plug. (see via GM GDS2, Tech2, or other high-end professional scan tool capable of reading manufacturer-specific symptom bytes.)
• C0045 06: Circuit Low Voltage / Open. Points specifically to an open wire, poor connection, or a short to ground. (see via GM GDS2, Tech2, or other high-end professional scan tool capable of reading manufacturer-specific symptom bytes.)
• C0045 0F: Erratic Signal. Points towards a wiring issue, a poor connection, a damaged/dirty tone ring, or electrical interference rather than a completely failed sensor. (see via GM GDS2, Tech2, or other high-end professional scan tool capable of reading manufacturer-specific symptom bytes.)
• C0045 18: Low Signal Amplitude. Suggests the signal from the sensor is too weak, often caused by an excessive air gap (see 'rust jacking') or an internally failing sensor. (see via GM GDS2, Tech2, or other high-end professional scan tool capable of reading manufacturer-specific symptom bytes.)
• C0045 5A: Signal Plausibility Failure. The EBCM is receiving a signal, but it doesn't logically match the signals from the other wheel speed sensors (e.g., three wheels at 40 MPH, one at 5 MPH). (see via GM GDS2, Tech2, or other high-end professional scan tool capable of reading manufacturer-specific symptom bytes.)

Scan Tool Commands That Help

• Tech2 / GDS2 / Pro-level Scanner: Live Data Graphing — This is the primary diagnostic step. Graphing all four wheel speeds simultaneously during a slow test drive will make an erratic or non-reporting sensor immediately obvious as a glitchy or flat line compared to the other three smooth lines.
• Jumper Wires & Scan Tool: Signal Substitution Test — To definitively isolate the fault to the sensor/hub assembly. Unplug the left and right rear sensors. Use long jumper wires to connect the good right rear sensor to the left rear vehicle harness connector. Clear codes and drive. If the code changes from C0045 to C0050 (Right Rear), it proves the EBCM and the entire wiring harness for the left side are good, condemning the original left rear sensor.

Wiring & Ground Locations

• EBCM Ground (G110) — Bolted to the outside of the driver's side frame rail, directly below the driver's door area. It can be identified as a heavy (approx. 12-gauge) black wire.. This is the main ground for the Electronic Brake Control Module. Its exposed location makes it highly susceptible to rust and corrosion. A poor ground here can cause numerous erratic ABS faults, including phantom single-wheel codes, before it fails completely and causes total communication loss.
• Left Rear WSS Connector — The sensor's harness connector is located up on the frame, typically behind the rear shock absorber.. This connector is a common point for moisture intrusion and corrosion. It's also where the harness can get stressed or damaged during suspension work.
• EBCM Connector (X1) — On the Electronic Brake Control Module, which is mounted to the ABS hydraulic unit on the inboard side of the driver's frame rail.. This is the termination point for the sensor circuit. Testing for continuity between this connector and the sensor connector can confirm if the wiring harness is intact. The Left Rear WSS signal wires are typically at pins A5 and A6.

Real Owner Repair Stories

• Tahoe Yukon Forum (2007-2014 Tahoe/Suburban (multiple users)) — ABS and StabiliTrak lights on, code C0045-00.
  ❌ Tried (didn't work) Replacing the left rear sensor with a Dorman part., Replacing the sensor a second time with another Dorman part., Replacing the sensor a third time with a Duralast part from AutoZone.
  ✅ What actually fixed it One user reported swapping the left and right rear sensors, which caused the code to change to C0050, confirming the sensor was bad. The final fix was installing a genuine ACDelco/GM sensor, with a strong warning that aftermarket sensors for this application are frequently faulty out of the box or fail very quickly.

OEM Part Supersession History

• 15121067, 20763147 → 20938122 — Standard part number consolidation and potential minor revisions by GM over the vehicle's lifespan.
  Heads up: No known incompatibilities. The newest part number, 20938122, is the correct service replacement for all 2007-2014 models. Aftermarket cross-references include Dorman 970-041, Standard Motor Products ALS1464, and NTK AB0112.

Model Year Variations Within This Range

• 2007-2014: No significant variations have been identified for the rear wheel speed sensor circuit within this generation. The sensor remained a separate, bolt-in component on the rear axle for all model years.

Diagnostic Flowchart

Used vs. New Parts: Buying Guide for This Vehicle

When a used part is the smart pick: A used wiring pigtail connector from a junkyard is a viable and cost-effective option if your original connector is damaged or corroded. The sensor itself should not be purchased used.

Donor-vehicle mileage cap: roughly under 150000 miles for the part to have meaningful remaining life.

What to inspect on the donor part:

• For a wiring pigtail, inspect for flexible, uncracked wire insulation.
• Ensure connector pins are straight and free of green or white corrosion.
• Cut the pigtail with as much wire as possible to make splicing easier.

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

• Rear Wheel Speed Sensor

Brands owners have reported issues with on this vehicle:

• Dorman
• Duralast

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. It is directly related as it can appear during diagnosis when swapping sensors side-to-side. It also shares the exact same common causes (sensor failure, wiring damage) as C0045, just on the opposite side of the vehicle.
• C0035 — This code corresponds to the Left Front Wheel Speed Sensor. It is related because it is part of the same ABS and StabiliTrak system. A fault in this circuit would trigger the same warning lights and symptoms.
• C0040 — This code corresponds to the Right Front Wheel Speed Sensor. Like C0035, it is part of the same vehicle stability system and a fault would result in similar symptoms, such as the ABS and StabiliTrak lights illuminating.
• C0561 — System Disabled Information Stored. This is a common companion code on GM vehicles. The Electronic Brake Control Module (EBCM) sets this code to indicate that it has disabled the StabiliTrak and Traction Control systems because of a critical fault in a required input, such as the failed wheel speed sensor indicated by C0045.

Frequently Asked Questions