U0126 on 2015-2019 GMC Sierra 3500: Causes for Lost Communication With Steering Angle Sensor

What's Unique About the 2015-2019 Gmc SIERRA 3500

For this generation of Sierra HD trucks (K2XX platform), the U0126 code is very frequently a symptom of specific, well-documented wiring problems, not a failed sensor. General Motors has issued multiple Technical Service Bulletins (TSBs) that direct technicians to check for a pinched harness between the left instrument panel mounting bracket and the body, and for chafed wires under the door sill plates. Another common culprit is a poor Body Control Module ground (G218) under the driver's side dash, where sound-deadening material can get trapped under the connection. These known weak spots make a thorough wiring and ground inspection the mandatory first step before considering replacing any parts.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Symptoms You May Notice

• "Service StabiliTrak" message on the instrument cluster
• Illuminated ABS warning light
• Illuminated Traction Control/StabiliTrak light
• Loss of cruise control functionality
• Reduced or intermittent power steering assist, making the wheel feel heavy
• Inoperative rear wiper or dead battery (as noted in TSB #PIT5288G)
• Flickering dash lights or headlights, especially when turning the wheel 🎬 Watch: How to locate and clean the G218 ground connection. (symptom of poor G218 ground)
• Backup camera grid lines may be missing

Most Likely Causes

1. Pinched or Damaged Wiring Harness 🔴 High Probability As documented in GM TSBs #PIT5288G/H and #PIT5457D, wire harnesses on this platform are known to be pinched or chafe in specific locations, causing shorts or open circuits on the communication network.
   How to confirm: Visually inspect the dash harness where it passes the left I/P mounting bracket, near the parking brake pedal; it can get pinched between the bracket and the body. Also, remove the driver and passenger door sill plates and inspect the harness channel, looking for chafed wires, especially the 'Communication Enable' wire (Circuit 5986).
   Typical fix: Carefully repair the damaged section of the wire(s) using solder and heat shrink or quality butt connectors. Reroute the harness slightly or add protective conduit/tape to prevent future damage. Loosening the I/P bracket may be needed to free a pinched harness.
   Est. part cost: $5-$25
2. Poor BCM Ground (G218) 🔴 High Probability TSB #PIT5405C points to the Body Control Module (BCM) ground G218 as a common source of various electrical issues. During assembly, sound-deadening insulation foam can get trapped between the ground terminal and the chassis, creating high resistance and causing modules to drop off the network, especially under electrical load (like turning the steering wheel).
   How to confirm: Access ground G218, located under the driver's side of the dashboard, typically near the A-pillar and speaker. Remove the nut and check for any foam or foreign material under the eyelet terminal. The connection may look tight but still have high resistance.
   Typical fix: Remove the ground nut, pull back the terminal, and trim away any insulating foam caught underneath. Scuff the terminal and the chassis stud with a wire brush to ensure a clean metal-to-metal contact, then securely retighten the nut.
   Est. part cost: $0-$5
3. Faulty Steering Angle Sensor (SAS) Module ⚪ Low Probability → Shop Steering Angle Sensor While less common than wiring issues on this truck, the sensor itself can fail internally. The SAS is often integrated with the clock spring assembly behind the steering wheel.
   How to confirm: After confirming the wiring (including power, ground, and CAN bus lines to the sensor) is intact and the G218 ground is clean, a professional scan tool can be used to attempt to communicate directly with the SAS module. If it doesn't respond despite having good power and ground, the module is likely faulty.
   Typical fix: Replace the Steering Angle Sensor module. This requires removing the steering wheel and airbag. 🎬 See this walkthrough for replacing the steering position sensor. A calibration procedure with a compatible scan tool is mandatory after installation for the StabiliTrak system to function.
   Est. part cost: $75-$350

Rare But Worth Checking

• Faulty Electronic Brake Control Module (EBCM): → Shop ABS Control Module The EBCM is a primary user of the SAS data. While rare, an internal failure in the EBCM can sometimes disrupt network communication and cause other modules to report lost communication.
• Power Steering Control Module (PSCM) Software Error: TSB #20-NA-113 indicates that on some models, a software glitch in the PSCM can cause communication codes like U0126 to remain as 'current' faults even after the initial problem (like a low battery) is fixed. The solution is to have a dealer reprogram the PSCM with the latest software.

Diagnosis Steps

1. Read all fault codes from all vehicle modules using a professional scan tool capable of accessing Chassis and Body systems.
2. Check and record any other 'U' codes present, as they can point to the root cause.
3. Check battery voltage and charging system health. Ensure voltage is stable and above 12.4V with the engine off.
4. Access and inspect ground G218 under the driver's side dash near the speaker. Remove the nut and trim away any trapped insulation foam, clean the contacts, and retighten.
5. Perform a detailed visual inspection of the wiring harness in the left instrument panel area, near the parking brake mechanism, for pinching against the metal dash bracket, as specified in TSB #PIT5288H.
6. Remove the driver and passenger sill plates and inspect the wiring harness running along the floor for any signs of damage, paying close attention to the Communication Enable wire (Circuit 5986), as specified in TSB #PIT5457D.
7. If wiring damage is found, repair the affected wires, clear all codes, and re-test.
8. If wiring appears intact, use a multimeter to check for stable power, a clean ground, and CAN bus signals at the Steering Angle Sensor connector.
9. If power, ground, and network lines are good, the final step is to suspect a faulty Steering Angle Sensor module. Replacement and calibration are then required.

Parts You'll Likely Need

• Steering Angle Sensor (OEM #13590209) — If wiring and grounds are confirmed to be good, the sensor module itself is the next most likely point of failure. This part requires calibration after installation. 🎬 Watch: How to perform the mandatory steering angle sensor calibration.
  Trusted brands: ACDelco (GM Genuine), Dorman, Standard Motor Products
  OEM price range: $75-$150
  Aftermarket price range: $60-$120
• Wiring Repair Supplies — Given the high probability of a wiring or ground issue, supplies like automotive-grade wire, butt connectors, heat shrink tubing, and Tesa tape are often all that's needed for the fix.
  OEM price range: $5-$25
  Aftermarket price range: $5-$25

Related Codes That Often Appear With This One

• U0077 — Indicates a general communication fault on the High-Speed CAN bus, often set alongside specific module codes like U0126. It's mentioned in both TSBs #PIT5288G and #PIT5457D.
• U0121 — Indicates 'Lost Communication With Anti-Lock Brake System (ABS) Control Module'. This points to a wider network problem affecting chassis control systems, often caused by the same wiring issue on circuit 5986. It's cited in TSB #PIT5457D.
• U0415 — Indicates 'Invalid Data Received From ABS Control Module'. This often appears with U0126 because the ABS/StabiliTrak system relies on data from the Steering Angle Sensor. It's cited in TSB #PIT5288G and #PIT5457D.
• U0131 — Indicates 'Lost Communication with Power Steering Control Module'. This is often set along with U0126 as they are both on the same communication bus and related to steering functions. TSB #PIT5457D lists it as a related code.

Technical Service Bulletins (TSBs) & Recalls

• PIT5288G/H: Notes that a pinched wire harness in the left instrument panel can cause U0126 and a variety of other electrical faults.
• PIT5457D: Cites a wire harness under the sill plates (specifically Circuit 5986) as a potential cause for loss of communication codes, including U0126.
• PIT5405C: Mentions the BCM ground G218 as a source of communication issues.
• 20-NA-113: Describes a PSCM software issue that can cause codes like U0126 to be stored incorrectly after a low voltage event.

Platform-Specific Known Issues

• TSB #PIT5288G/H documents a known issue where the wire harness in the left instrument panel can become pinched between the dash mounting bracket and the body, causing U0126 and other communication codes.
• TSB #PIT5457D points to another common issue where the 'Communication Enable' wire (Circuit 5986) in the harness under the driver and passenger sill plates can be damaged, leading to loss of communication with the EBCM and SAS.
• TSB #PIT540

Mechanic-Grade Diagnostic Values

• High-Speed CAN Bus Network Resistance — expected: 60 ohms (+/- 5 ohms). Failure: A reading of 120 ohms indicates an open circuit or a missing terminating resistor. A reading significantly less than 60 ohms indicates a short between the CAN High and CAN Low wires.
• High-Speed CAN Bus Voltage (Key On, Engine Off) — expected: CAN High (Pin 6 to Ground): ~2.6V. CAN Low (Pin 14 to Ground): ~2.4V.. Failure: Voltages that are the same (e.g., both 2.5V) can indicate a short between the wires. 0V on both can indicate a short to ground.
• Communication Enable Circuit (5986) Voltage — expected: ~12V (Battery Voltage). Failure: Low or no voltage indicates an open, short, or high resistance in the circuit, often under the driver's or passenger's sill plate.

Scan Tool Commands That Help

• GM GDS2 / Professional Scan Tool: Steering Angle Sensor Learn/Calibration — This procedure is mandatory after replacing the Steering Angle Sensor or the Electronic Brake Control Module (EBCM). It is also required after performing a wheel alignment to ensure the sensor's zero position corresponds to the wheels being straight ahead.
• GM GDS2 / Professional Scan Tool: Module Communication Test / Device Control — To isolate a fault, a technician can attempt to communicate directly with individual modules on the CAN bus (like the SAS, EBCM, PSCM). If all other modules respond except for the SAS, and its power/ground/network wiring is verified as good, it points to an internal failure of the SAS module.

Wiring & Ground Locations

• G218 — Under the driver's side of the dashboard, behind the A-pillar side trim panel, near the speaker. It is a ground stud on the body.. This is the primary ground for the Body Control Module (BCM). As documented in TSB #PIT5405C, sound-deadening foam can get trapped under the ground terminal, causing high resistance and leading to numerous communication codes, including U0126, especially when electrical load increases (like when turning the wheel).
• Circuit 5986 (Communication Enable) — Runs in the main body harness under both the driver's and passenger's side door sill plates.. This circuit is the 'wake-up' signal sent from the BCM to modules like the SAS, EBCM, and PSCM. TSB #PIT5457D identifies this wire as a common point of failure due to corrosion or damage from moisture under the sill plates, causing a loss of communication.
• Splice J365 — Located in the wiring harness under the passenger's front door sill plate.. This is a splice point for the Communication Enable circuit (5986). It is a known area for corrosion to develop, creating an open or high resistance that prevents modules downstream from waking up and communicating.
• Steering Angle Sensor Connector — Located on the steering column, connecting to the clock spring/SAS assembly, behind the steering wheel.. This is the direct connection to the sensor. Pinpoint tests for power, ground, and CAN bus signals are performed here to determine if the fault is in the vehicle wiring or the sensor itself.

Real Owner Repair Stories

• YouTube user Robert Corona / documented by another user (2014 Chevrolet Silverado) — Service Stabilitrak message, various electrical issues, DTC U0121 (Lost comms with EBCM) and other communication codes.
  ❌ Tried (didn't work) Initial diagnosis was difficult.
  ✅ What actually fixed it A dealership technician found a voltage drop at ground G218. The fix was to access the ground under the driver's dash, find the sound-deadening material trapped under the ground wire terminal, cut the material away, and re-secure the ground connection. This permanently resolved the electrical issues and warning messages.

OEM Part Supersession History

• 13590209 → No supersession found. 13590209 appears to be the current and consistent part number for the entire 2015-2019 model year range. — N/A
  Heads up: This part requires programming and/or special setup procedures after installation. GM Service Information describes the necessary steps to ensure proper operation.