C0055 on 2007-2013 Chevrolet Suburban: Rear Speed Sensor Circuit Fault Guide

What's Unique About the 2007-2013 Chevrolet SUBURBAN

The GMT900 platform, which includes the 2007-2013 Suburban, is known for a specific mechanical failure that triggers this code. A press-fit tone wheel (or reluctor ring) inside the transfer case tail housing can come loose and spin on the output shaft, creating an erratic signal. This issue is so common that GM issued a Technical Service Bulletin (PIP4966B) about it, which applies to transfer cases with RPO codes NQG, NQF, NQH, and NQG. While the sensor itself can fail, checking for this loose tone wheel is a critical, platform-specific diagnostic step that is often overlooked, especially when a C0055-5A (erratic signal) code is present.

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
• "Service StabiliTrak" or "Service Traction Control" message on the Driver Information Center
• Cruise control is disabled
• Potential for harsh or erratic transmission shifting
• Speedometer may be erratic or inoperative at times

Most Likely Causes

1. Loose or Damaged Tone Wheel (Reluctor Ring) 🔴 High Probability As noted in TSB #PIP4966B, the press-fit tone wheel on the transfer case output shaft is known to loosen over time, causing it to spin independently of the shaft and generate an erratic signal. This is the most common cause when the symptom byte is '5A'.
   How to confirm: Remove the rear driveshaft and the VSS sensor. Attempt to move the tone wheel with a pick or screwdriver through the sensor hole. Any movement confirms it is loose. A visual inspection requires removing the transfer case tail housing.
   Typical fix: The loose tone wheel must be secured or replaced. A common and permanent DIY/shop fix is to tack-weld the ring to the shaft in three or four spots. 🎬 Watch: A mechanic demonstrates welding the tone ring for a permanent fix. The official GM repair is often to replace the entire output shaft, which comes with a new, securely-fitted tone wheel.
   Est. part cost: $50-$400
2. Failed Rear Vehicle Speed Sensor (VSS) 🟡 Medium Probability → Shop Drive Shaft Sensor The sensor is exposed to heat and the elements at the back of the transfer case/transmission, leading to eventual electronic failure. This is a more likely cause if the symptom byte is '00' (circuit fault).
   How to confirm: With a scan tool, monitor the rear wheel speed data; if it's absent or erratic and the tone wheel is confirmed to be secure, the sensor is the likely culprit. It can also be tested with a multimeter for resistance, which should be approximately 1300-2900 ohms.
   Typical fix: Replace the Vehicle Speed Sensor. It is held in by a single bolt (typically 13mm or 19mm). 🎬 See this walkthrough on how to replace the speed sensor.
   Est. part cost: $25-$80
3. Damaged Wiring Harness ⚪ Low Probability The VSS wiring harness runs over the top of the transmission and transfer case, where it can chafe against the bellhousing or vehicle body, leading to a short or open circuit. Rodent damage under the fuse box has also been reported as a cause.
   How to confirm: Visually inspect the entire length of the VSS harness from the sensor to the main loom. Pay close attention to the area on top of the transmission between the firewall and the back of the engine. Check for continuity and shorts using a multimeter.
   Typical fix: Repair the damaged section of the wire and protect it from future chafing with loom or by re-routing. The pigtail connector itself can also fail and be replaced.
   Est. part cost: $5-$25

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 (tone wheel, sensor, wiring) have been definitively ruled out. A lab scope can be used to verify a good square wave signal is reaching the EBCM; if the signal is present but the code persists, the EBCM may be at fault.

Diagnosis Steps

1. Connect a professional scan tool capable of reading ABS codes and live data. Confirm C0055 is present. Note if it is a '00' (circuit) or '5A' (erratic signal) sub-type, as '5A' strongly suggests a mechanical tone wheel issue.
2. Raise the vehicle securely on a lift.
3. Visually inspect the Vehicle Speed Sensor (VSS) and its connector on the rear of the transfer case (4WD) or transmission (2WD). Check for obvious damage or corrosion.
4. Trace the wiring harness from the sensor up over the transmission bellhousing, looking for any signs of chafing, melting, or breaks, which is a common failure point.
5. If wiring looks good, remove the VSS (one bolt). Look through the hole at the tone wheel (reluctor ring).
6. Use a long screwdriver or pick to gently poke the tone wheel. If it moves or spins at all, it has failed and is the source of the code. This is the most critical step.
7. If the tone wheel is solid, test the VSS itself. With a multimeter, check the resistance between the two pins of the sensor. A reading between 1300-2900 ohms is expected.
8. If the tone wheel is secure and the sensor tests bad or produces no signal, replace the sensor.
9. If the tone wheel is loose, the transfer case tail housing must be removed to either tack-weld the ring in place or replace the output shaft.
10. After repairs, clear the codes and perform a test drive to ensure the ABS and StabiliTrak lights stay off.

Parts You'll Likely Need

• Vehicle Speed Sensor (VSS) (OEM #ACDelco 213-4520 (GM 20938122), 20938122) — This sensor generates the rear wheel speed signal. It can fail electronically, causing a loss of signal (often C0055-00).
  Trusted brands: ACDelco, Delphi, Standard Motor Products
  OEM price range: $40-$75
  Aftermarket price range: $25-$50
• Transfer Case Output Shaft Tone Wheel — This is the primary mechanical failure point for code C0055 on this platform, especially C0055-5A. The ring loosens on the shaft, causing an erratic signal. The part is not sold separately from the output shaft by GM.
  OEM price range: $200-$400 (for shaft assembly)
• VSS Connector Pigtail (OEM #Standard Motor Products S2412 (Aftermarket)) — The connector at the sensor can become brittle or corroded, or the wiring can chafe nearby, requiring replacement of the pigtail.
  Trusted brands: Standard Motor Products (SMP), Dorman
  Aftermarket price range: $15-$40

Related Codes That Often Appear With This One

• P2771 — TSB #PIP4966B explicitly links C0055 with P2771 (Four-Wheel Drive (4WD) Low Switch Circuit). This is because the Transfer Case Control Module (TCCM) uses the same speed sensor data, and a fault can trigger codes in related systems.

Technical Service Bulletins (TSBs) & Recalls

• PIP4966B: Notes that C0055 can be caused by a loose tone wheel or output shaft in the transfer case.
• PIT4815C: Provides specific electrical testing steps for the rear speed sensor circuit when C0055 is set.

Platform-Specific Known Issues

• TSB #PIP4966B documents that DTC C0055 can be caused by 'excess movement of the tone wheel or output shaft', pointing to a known mechanical weakness within the transfer case. It also notes this can cause unwanted ABS activation or transmission-related codes.
• TSB #PIT4815C provides specific electrical diagnostic procedures for technicians to follow when C0055 is the only code present, indicating a known pattern of circuit faults that requires checking signal frequency.

Mechanic-Grade Diagnostic Values

• Vehicle Speed Sensor (VSS) internal resistance — expected: 1300-1426 ohms. Failure: An open loop (OL) reading or resistance significantly outside the expected range.
• VSS AC Signal Output (Raw, at sensor) — expected: Approx. 1.0V peak-to-peak AC sine wave when the driveshaft is spinning at one revolution per second.. Failure: No AC voltage, or a weak/distorted sine wave while the shaft is turning.
• Processed Speed Signal Frequency (at EBCM, Circuit 817) — expected: Approximately 1.1 Hz per 1 MPH.. Failure: Signal is absent, erratic, or does not correspond to vehicle speed.
• Raw Speed Signal Frequency (at sensor) — expected: Approximately 25 Hz per 1 MPH of driveshaft speed.. Failure: Signal is absent, erratic, or does not correspond to driveshaft speed.

Hidden / Shadow Codes Worth Checking

• C0055 00: Indicates the EBCM has detected a circuit fault, such as an open, a short to ground, or a short to voltage in the rear wheel speed sensor circuit. This often points to a wiring issue or a completely failed sensor. (see via A professional scan tool capable of reading GM-specific ABS codes and symptom bytes, like a Tech2 or GDS2.)
• C0055 5A: Indicates the EBCM has detected an erratic or implausible signal from the rear wheel speed sensor. This is the specific sub-code that strongly points to a mechanical issue like a loose tone wheel, as the signal is present but not rational. (see via A professional scan tool capable of reading GM-specific ABS codes and symptom bytes, like a Tech2 or GDS2.)

Scan Tool Commands That Help

• GDS2 / Tech2: Module Diagnostics -> EBCM -> Data Display — To monitor the 'Rear Wheel Speed' or 'Vehicle Speed' PID in real-time while driving. This allows you to see if the signal is dropping out, erratic, or completely absent, which helps differentiate between a constant circuit fault (C0055-00) and an intermittent mechanical one (C0055-5A).
• GDS2 / Tech2: Vehicle DTC Information -> Clear All DTCs — After a repair is completed, this function is used to clear the C0055 code from the EBCM's memory. A test drive is required afterward to confirm the fault does not return.
• Snap-on or similar with Lab Scope: Lab Scope -> Signal Test at EBCM — To visually inspect the square wave signal arriving at the EBCM. If a clean square wave is present but the code is set, it confirms the sensor, wiring, and preceding modules are good, pointing to a rare internal failure of the EBCM itself.

Wiring & Ground Locations

• EBCM Ground — On the frame rail directly under the driver's side door area, near the EBCM itself.. A corroded or loose main ground for the Electronic Brake Control Module (EBCM) can cause a variety of erratic ABS codes, including C0055, due to unstable power or reference. Cleaning this ground point is a common fix for intermittent ABS issues on GM trucks.
• VSS Signal Wires — A twisted pair of wires (often purple/white and green/black) running from the VSS on the transfer case, up over the top of the transmission bellhousing, and into the main harness near the firewall.. This harness is a very common point for chafing and rubbing, which can cause the wires to short out or break, resulting in a C0055-00 (circuit fault) code.
• EBCM Connector (Pin B3) — The main harness connector at the Electronic Brake Control Module (EBCM).. Pin B3 is a specific pin for the rear wheel speed sensor signal. A diagnostic step involves checking for continuity from the ECM to this pin to verify the integrity of the wiring harness.

Real Owner Repair Stories

• PerformanceTrucks.net forum user (2007 Chevrolet Silverado) — Erratic/twitching speedometer, harsh transmission shifting, and DTC C0055.
  ❌ Tried (didn't work) Replacing the Vehicle Speed Sensor (VSS) on the transfer case.
  ✅ What actually fixed it The owner discovered that the VSS wiring harness had rubbed through where it runs over the top of the transmission, between the firewall and the back of the engine. Repairing the damaged wires in this specific location resolved all symptoms and cleared the code.
• DuramaxDiesels.com forum user (2006 Duramax (similar GMT800 platform but relevant failure mode)) — ABS code C0055 present, but no ABS light or noticeable driving issues.
  ❌ Tried (didn't work) Testing sensor resistance (read 1362 ohms, seemed normal)., Checking wiring from TCM to sensor for shorts (all good).
  ✅ What actually fixed it The user noted a worn slip yoke bushing in the transfer case. It was suspected that this wear allowed the tone ring to make contact with the VSS, damaging it. After clearing codes and topping off fluid, the code did not immediately return, but the underlying mechanical play was the likely root cause. This highlights how internal transfer case wear can directly lead to C0055.

OEM Part Supersession History

• 15121067, 20763147 → 20938122 — Standard part revision and consolidation by GM.

Model Year Variations Within This Range

• 2007-2013: While the C0055 fault is common across the range, the specific transfer case model may vary. TSB PIP4966B applies to RPO codes NQF, NQG, NQH. The RPO code sticker, typically found in the glove box, should be checked to confirm which transfer case is installed as internal parts may differ slightly.