C0050 on 2008-2009 Pontiac G8: Right Rear Wheel Speed Sensor Fault Causes and Fixes

What's Unique About the 2008-2009 Pontiac G8

The Pontiac G8, based on the Australian Holden Commodore (VE), is known for having the wheel speed sensor wiring become brittle and break, particularly right at the connector behind the wheel hub. Owners frequently report finding a snapped wire as the root cause of a C0050 code, sometimes making a simple sensor replacement ineffective if the harness isn't repaired first. This wiring vulnerability appears to be more common than the sensor failing on its own and is a well-documented issue on G8 and Holden enthusiast forums.

Symptoms You May Notice

• ABS warning light is on
• Traction Control or StabiliTrak warning light is on
• "Service StabiliTrak" or similar message on the driver information center
• ABS and Traction Control systems are disabled and will not function

Most Likely Causes

1. Broken or Damaged Wiring Harness 🔴 High Probability The wiring leading to the wheel speed sensor is exposed to the elements and constant suspension movement. On the G8 and its Holden platform mates, the wire is known to fatigue and break right at the connector where it has the least slack and is subject to stress.
   How to confirm: Visually inspect the wiring harness that plugs into the right rear wheel speed sensor. Carefully pull on each wire at the connector; a broken wire will stretch or come apart. Check for corrosion inside the connector pins. The break is often within an inch of the connector and can be hidden by the insulation.
   Typical fix: Repair the broken wire using a new pigtail connector. Soldering and heat-shrinking the connection is the most durable repair. Ensure there is enough slack to prevent future stress. Some owners have successfully re-pinned the connector if the break is close enough. The entire rear harness is also available (Holden P/N 92286939).
   Est. part cost: $15-$40 for a pigtail connector
2. Failed Wheel Speed Sensor 🟡 Medium Probability → Shop ABS Wheel Speed Sensor The wheel speed sensor is integrated into the wheel hub/bearing assembly on the rear of the Pontiac G8. The internal sensor can fail electronically, or the magnetic encoder ring on the hub can become damaged or contaminated. The sensor itself is not serviced separately from the hub by GM for the G8.
   How to confirm: Using a scan tool that can read ABS live data, monitor the right rear wheel speed while driving. If the speed reads 0 or is erratic compared to the other wheels, and the wiring is confirmed to be good, the sensor/hub is faulty. You can also check for a proper signal with an oscilloscope at the sensor connector.
   Typical fix: Replace the entire right rear wheel hub assembly. The sensor is not sold separately by GM, though some aftermarket sensors are available that can be replaced without changing the hub.
   Est. part cost: $100-$250 for a hub assembly, or ~$25 for an aftermarket sensor-only.
3. Damaged or Contaminated Reluctor Ring ⚪ Low Probability The magnetic reluctor ring (or encoder) is part of the wheel hub assembly. If it cracks, rusts, or gets coated in metallic debris, it can produce an erratic or missing signal. This is a known issue on many GM vehicles of this era.
   How to confirm: Visually inspect the inboard side of the wheel hub assembly for cracks, swelling from rust, or a build-up of metallic shavings. This may require removing the hub to inspect thoroughly. A borescope can sometimes be used to inspect it through the sensor hole.
   Typical fix: The reluctor ring is not serviced separately. The entire wheel hub assembly must be replaced.
   Est. part cost: $100-$250

Rare But Worth Checking

• Faulty Electronic Brake Control Module (EBCM): → Shop ABS Control Module This is rare. Before condemning the EBCM, all other possibilities (wiring, sensor, hub) must be exhaustively ruled out. An EBCM failure would typically require professional diagnosis and programming after replacement.

Diagnosis Steps

1. Connect an ABS-capable scan tool to the vehicle.
2. Confirm the presence of code C0050. Note if there are any symptom bytes like '00' (circuit malfunction), '0F' (erratic signal), '18' (low signal amplitude), or '5A' (plausibility failure), as these can help pinpoint the fault.
3. Use the scan tool to monitor live data from all four wheel speed sensors. Drive the vehicle slowly (above 13 mph / 20 km/h) in a straight line.
4. Observe the reading from the Right Rear (RR) wheel speed sensor. Does it read 0 MPH while the others are working? Is it erratic or does it drop out?
5. Raise and safely support the rear of the vehicle.
6. Thoroughly inspect the wiring harness leading to the RR wheel speed sensor. Check for chafing, melting, or breaks, paying close attention to the area where the harness plugs into the hub. Gently tug on the wires at the connector to check for internal breaks.
7. Disconnect the sensor and inspect the connector pins for corrosion, moisture, or damage. A diagnostic aid from GM suggests spraying a saltwater solution on the harness to simulate moist conditions that can cause intermittent faults.
8. If the wiring looks good, and the scan tool showed a bad signal, the wheel hub/sensor assembly is the most likely culprit.
9. If you have an oscilloscope, you can back-probe the sensor connector to check for a clean square wave signal while spinning the wheel. A missing or erratic waveform points to a bad sensor or reluctor ring.
10. If wiring and the sensor/hub assembly are confirmed to be good, the issue may lie within the EBCM, which requires advanced diagnostics, such as checking for the 12-volt reference signal at the module itself.

Parts You'll Likely Need

• Rear Wheel Bearing and Hub Assembly (OEM #ACDelco 92171057, GM 92225321) — This assembly contains the integrated wheel speed sensor and the magnetic reluctor ring. If either fails, the entire hub must be replaced.
  Trusted brands: ACDelco, Timken, MOOG, National
  OEM price range: $200-$300
  Aftermarket price range: $100-$250
• ABS Wheel Speed Sensor Connector Pigtail (OEM #ACDelco PT2307) — The wires often break right at the connector, making this part necessary for a durable repair.
  Trusted brands: Dorman (e.g., 645-509, though listed for other applications, it is visually similar and may work), ACDelco, Standard Motor Products (e.g., S-575, HP4720)
  OEM price range: $30-$50
  Aftermarket price range: $15-$40
• Rear ABS Wheel Speed Sensor (Aftermarket Only) (OEM #GM 92211237 (Holden part number)) — While GM does not service the sensor separately from the hub for the G8, its Holden counterpart does. Aftermarket suppliers offer the sensor alone, which can be replaced without changing the entire hub assembly.
  Trusted brands: Holstein, Autopart Premium
  OEM price range: N/A
  Aftermarket price range: $20-$50

Related Codes That Often Appear With This One

• C0045 (Left Rear Wheel Speed Sensor Circuit)

Technical Service Bulletins (TSBs) & Recalls

• GM Corporate Bulletin 08-05-25-004: While not specific to the G8, this TSB addresses DTCs C0035-C0052 on other GM vehicles and advises a specific diagnostic component test procedure before replacing parts, highlighting that wiring and sensor issues are common.

Platform-Specific Known Issues

• A common failure point is the wiring within an inch of the sensor connector, which can break internally while the insulation looks intact.
• Forum users on GRRRR8.net and g8board.com consistently advise checking the wiring harness before replacing the hub, as many have wasted money on a hub replacement when only a pigtail was needed.
• While C0050 is a wheel speed circuit code on the G8, cross-manufacturer records such as NHTSA ODI #10763888 for other GM models like the Chevrolet HHR indicate that this code can sometimes identify a faulty power steering control module (PSCM) or steering column issue in different electrical architectures.

Mechanic-Grade Diagnostic Values

• Wheel Speed Sensor Type — expected: Active (3-wire Magnetoresistive type). Failure: This is not a passive sensor that generates its own AC voltage. Do not test for resistance as you would with an older 2-wire sensor; readings will be in the Mega-Ohm range or open, which is normal for this type but can be misleading.
• Sensor Supply Voltage at Connector — expected: Approx. 12 Volts (Ignition ON). Failure: If the 12V reference voltage is missing from the EBCM, it indicates a wiring problem between the module and the sensor, or a fault within the EBCM itself.
• Live Data Scan Tool Reading — expected: All four wheel speed sensors should report the same speed (+/- 1-2 mph) when driving straight above 13 mph (20 km/h).. Failure: The right rear sensor reads 0, is intermittent, or shows a speed that is wildly different from the other three wheels.

Hidden / Shadow Codes Worth Checking

• C0050 00: Circuit Malfunction. This is a general code pointing to an open, short to ground, or high resistance in the sensor circuit. (see via Professional scan tool (e.g., GM Tech2/GDS2) capable of reading GM-specific symptom bytes.)
• C0050 5A: Plausibility Failure. The EBCM is receiving a signal, but it doesn't make sense compared to the other wheel speed sensors (e.g., one wheel showing 5 mph while others show 40 mph). This can point to a damaged reluctor ring or debris on the sensor. (see via Professional scan tool (e.g., GM Tech2/GDS2) capable of reading GM-specific symptom bytes.)
• C0050 18: Low Signal Amplitude. The signal from the sensor is weak. This is often caused by an excessive air gap between the sensor and the reluctor ring, or metallic debris contaminating the magnetic ring. (see via Professional scan tool (e.g., GM Tech2/GDS2) capable of reading GM-specific symptom bytes.)
• C0050 0F: Erratic Signal. The signal from the sensor is inconsistent or jumping around. This strongly points to a wiring issue, a loose connection, or a failing sensor. (see via Professional scan tool (e.g., GM Tech2/GDS2) capable of reading GM-specific symptom bytes.)

Scan Tool Commands That Help

• Tech2/GDS2 or equivalent: Live Data > EBCM > Wheel Speed Sensors — This is the primary diagnostic step. Observing the live data from all four wheels while driving is the fastest way to confirm which sensor is malfunctioning and how it is failing (e.g., no signal vs. erratic signal).
• Tech2/GDS2 or equivalent: Clear DTCs — After the repair is complete, the code must be cleared. The vehicle must then be driven above 13 mph (20 km/h) for the EBCM to run its self-test and turn off the ABS/TCS warning lights.

Wiring & Ground Locations

• EBCM Connector Pin 8 — At the main connector for the Electronic Brake Control Module (EBCM).. This is the specific pin for the Right Rear Wheel Speed Sensor Signal circuit. Testing for a signal or continuity at this pin can help determine if a wiring break is between the sensor and the module.
• G401 — In the rear compartment, on the left rear beam, near the battery.. This is a major chassis ground point in the rear of the vehicle. While not directly for the sensor, a poor ground here could potentially introduce electrical noise or issues into nearby circuits, though it's an unlikely cause for a single sensor code.
• Rear ABS Wiring Harness — Runs from a central point on the rear subframe out to both rear wheel hubs.. This harness is a known failure point. The wires, especially for the right rear sensor, are known to break right at the connector due to stress and exposure. The Holden part number for the complete rear harness is 92286939.

Real Owner Repair Stories

• GRRRR8.net forum user 'Niemer' (2008-2009 Pontiac G8 (specific year not mentioned)) — ABS/TCS lights on with code C0050.
  ❌ Tried (didn't work) Initial diagnosis pointed to the sensor, but visual inspection revealed the true cause.
  ✅ What actually fixed it The user found a broken wire right at the 4-pin connector for the right rear wheel speed sensor. The wire was broken too close to the connector to easily solder. The discussion confirmed this is a common failure and the solution is either to replace the pigtail, re-pin the connector, or replace the entire rear ABS harness (Holden P/N 92213408 was mentioned for the rear harness assembly).

OEM Part Supersession History

• Unknown → GM 92225321 / ACDelco 92171057 — Standard part evolution for the rear wheel hub assembly.
• Unknown → Holden 92286939 — This is the genuine Holden part number for the entire rear ABS wiring harness, which is a common replacement part for this issue on the underlying Commodore platform.

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 the complete rear ABS harness from a junkyard is a very sensible choice, as this is not a wear item and the failure is typically a simple wire break. This can be significantly cheaper than a new harness.

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 harness, inspect the connector closely. Ensure the plastic isn't brittle and the locking tab is intact.
• Gently tug on each wire at the back of the connector to ensure none are already broken internally.
• Check for at least 6-8 inches of clean wire past the connector to give you ample room to work.
• Avoid harnesses from vehicles with obvious signs of flood or fire damage.

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

• While not strictly 'OEM-only', using a reputable brand for the wheel hub assembly (ACDelco, Timken, MOOG) is highly recommended. Cheap, no-name hubs are notorious for premature bearing failure or poor quality magnetic encoder rings that can cause the same code to return.

Aftermarket brands forum-validated for this vehicle:

• Hub Assemblies: Timken, MOOG, SKF, National
• Wiring Pigtails: ACDelco, Dorman, Standard Motor Products (SMP)

Brands owners have reported issues with on this vehicle:

• Unnamed or 'white box' wheel hub assemblies from online marketplaces are a gamble and often lead to repeat repairs.

Real Owner Stories

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

Documented NHTSA Reports

Related OBD-II Codes

• C0045 — Indicates a fault with the Left Rear wheel speed sensor circuit. This code is frequently caused by the same wiring harness fatigue issue that triggers C0050, just on the opposite side of the vehicle. Both are covered by the diagnostic logic in GM TSB 08-05-25-004.
• C0040 — Points to a fault in the Right Front wheel speed sensor circuit. While the rear wiring is a more common failure point on the G8 platform, the front sensors and wiring can fail in a similar manner, disabling ABS and StabiliTrak.
• C0035 — Points to a fault in the Left Front wheel speed sensor circuit. This code shares the same potential causes as C0050, including a failed sensor integrated into the hub or a damaged wiring harness.
• C0051 — This code often indicates a performance or range issue with the Right Rear wheel speed sensor, rather than a hard circuit fault. It can be caused by an erratic signal from a damaged reluctor ring or an intermittent wiring connection, sharing the same root causes as C0050.

Frequently Asked Questions