U0131 on 2015-2019 GMC Sierra 3500: Power Steering Communication Loss Fixes

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

This generation of GMC Sierra HD trucks is well-documented by GM to have specific vulnerabilities that cause code U0131. Technical Service Bulletin #PIT5457D directly points to a wiring harness under the door sill plates that can get damaged, specifically implicating the 'Communication Enable Circuit 5986'. Another TSB, #PIT5405C (later superseded by #18-NA-161), identifies a poor ground connection at point G218 under the driver's side dash as a frequent culprit for this and other network codes. Furthermore, certain 2015 models were subject to GM Safety Recall #14743 for a defect that could cause a sudden loss of power steering and set this code. These known wiring and component issues are far more common than a random failure of the Power Steering Control Module itself.

Diagnostic Flowchart

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

Symptoms You May Notice

• Complete loss of power steering assist, making the steering wheel very heavy
• Power steering warning message on the instrument cluster ('Service Power Steering')
• Service ABS, Traction Control, or StabiliTrak warning lights may also illuminate
• Intermittent loss of steering assist that may correspond with vibration or hitting bumps
• Steering wheel jerks or kicks back when turning at low speeds.

Most Likely Causes

1. Damaged Wiring Harness Under Sill Plates 🔴 High Probability As cited in GM TSB #PIT5457D, the wiring harnesses running along the floor under the driver and passenger door sill plates are susceptible to damage from moisture, corrosion, or chafing. This can cause an open or short in the communication wires, specifically the Communication Enable Circuit (wire 5986).
   How to confirm: Remove the driver and passenger side plastic sill plates. Carefully peel back the carpet and inspect the entire length of the wiring harness for any signs of green corrosion, pinched wires, or previous poor repairs. TSB #PIT5457B also identifies splice J365 under the passenger sill plate as a potential failure point.
   Typical fix: Repair the specific damaged wire(s). This involves cutting out the corroded section, splicing in a new piece of wire using weatherproof butt connectors, and protecting the repair with heat shrink tubing.
   Est. part cost: $5-$20
2. Poor Ground at Location G218 🔴 High Probability GM TSB #PIT5405C and its successor #18-NA-161 note that the dash insulator mat can get trapped between the G218 ground terminal and the chassis during factory assembly. This prevents a solid metal-to-metal connection, leading to intermittent communication failures across multiple modules. This is a widely documented factory flaw.
   How to confirm: Locate ground G218 behind the driver's side kick panel, near the A-pillar and speaker, attached to a metal support brace. 🎬 Watch: How to fix the G218 ground connection issue. Disassemble the 10mm ground nut and check if the black insulation material is underneath the ring terminal. The connection should be clean.
   Typical fix: Remove the nut and terminal. Cut away the insulation around the ground stud. Clean the terminal and the chassis mounting point with an abrasive pad to ensure a bright metal finish, then securely re-fasten the connection.
   Est. part cost: $0
3. Blown Power Steering Fuse / Faulty Fuse Block 🟡 Medium Probability The electric power steering system draws significant current. A voltage spike or a short in the power steering motor can cause its main fuse to blow. This fuse is often integrated into the battery terminal fuse block.
   How to confirm: Check the high-amperage 'Mega' fuse for the power steering system. It is an 80A or 100A fuse located in a small, separate fuse box (Engine Wiring Harness Junction Block) attached to the positive battery terminal. Visually inspect if the fuse link is broken or test for continuity. If the fuse is part of the block, the entire block may need testing.
   Typical fix: If the fuse is separate, replace it. If it is integrated into the battery fuse block (OEM #84303175), the entire block must be replaced. If a new fuse blows immediately, there is an underlying short circuit in the power feed to the steering rack that must be diagnosed.
   Est. part cost: $5-$75
4. Faulty Power Steering Control Module (PSCM) ⚪ Low Probability While less common than wiring issues, the PSCM can fail. This was the cause for GM Safety Recall #14743 on some 2015 models, requiring replacement of the power steering assist motor kit. On other models, the module, which is integrated into the power steering rack assembly, can fail internally due to thermal stress or component age.
   How to confirm: This is diagnosed by exclusion. If all wiring, grounds, and fuses are confirmed to be good, and communication still cannot be established with the PSCM using a professional scan tool, the module itself is likely faulty. First, check if your VIN is part of recall #14743.
   Typical fix: For recalled vehicles, the dealer will replace the power steering assist motor kit at no charge. Otherwise, the entire power steering rack and pinion assembly must be replaced, as the control module is not sold separately. The new module will require programming to the vehicle.
   Est. part cost: $800-$1800

Rare But Worth Checking

• High Resistance in Negative Battery Cable:

Diagnosis Steps

1. CRITICAL: Check for open recalls. Enter your VIN on the NHTSA or GM website to check for Safety Recall #14743 (NHTSA ID 14V719000), especially for 2015 models. This could result in a no-cost repair at a dealership.
2. Scan all vehicle modules for codes. Note which other modules are reporting communication loss to identify a pattern.
3. Check the battery and charging system. Ensure voltage is stable and above 12.6 volts with the engine off. Per TSB #18-NA-161, ensure battery terminals are clean and torqued to 7 Nm (62 lb-in).
4. Perform a voltage drop test on the negative and positive battery cables as recommended in TSB #18-NA-161. High resistance (over 200mV) can cause phantom communication issues.
5. Inspect the main power steering mega fuse (80A-100A) in the fuse block on the positive battery terminal.
🎬 See this video to locate the power steering mega fuse.
6. CRITICAL: Inspect the G218 ground connection. Remove the driver's side kick panel, disassemble the 10mm ground nut, and ensure there is a clean, metal-to-metal connection with no trapped insulation.
7. CRITICAL: Inspect the wiring harnesses under the driver and passenger door sill plates for any signs of corrosion, damage, or water intrusion, as detailed in TSB #PIT5457D. Pay close attention to the Communication Enable Circuit (wire 5986) and Splice J365.
8. If all wiring and grounds are good, use a scan tool to check for power, ground, and CAN bus signals at the PSCM connector on the steering rack. On the 14-pin connector, Pin 12 (Tan/Black) is typically CAN High and Pin 13 (Tan) is CAN Low.
9. If power, ground, and network signals are present at the module but it still won't communicate, the PSCM (steering rack assembly) is likely faulty and requires replacement.

Parts You'll Likely Need

• Power Steering Rack and Pinion Assembly (OEM #84446361) — This part is only needed if all wiring and ground faults have been ruled out. The control module (PSCM) is integrated. This part supersedes 23412215, 84059834, 84073904, 84228166, and 84346954.
  Trusted brands: ACDelco, GM Genuine

Related Codes That Often Appear With This One

• U0140 — Lost Communication With Body Control Module (BCM). This code often appears with U0131 when the G218 ground is faulty, as it is a primary ground for the BCM.
• U0121 — Lost Communication With Anti-Lock Brake System (ABS) Control Module. The ABS and power steering systems work together. A network wiring fault under the sill plates, as mentioned in TSB #PIT5457D, can affect both modules simultaneously.
• U0073 — Control Module Communication Bus 'A' Off. This is a general code indicating the entire high-speed CAN bus is down, often caused by the same critical ground or wiring fault that triggers U0131.

Technical Service Bulletins (TSBs) & Recalls

• PIT5457D: Addresses loss of communication with various modules, including the PSCM, due to potential open or damaged wiring in the harness located under the driver and passenger sill plates.
• PIT5405C (and successor 18-NA-161): Addresses numerous electrical issues including U0131 caused by a poor ground at G218 (trapped insulation mat) and provides diagnostic procedures for battery cable voltage drops.

Platform-Specific Known Issues

• TSB #PIT5457D: Sill Plate Harness Damage: Documents that the wiring harness under the door sill plates is a common point of failure, leading to communication codes like U0131. The specific wire often implicated is the Communication Enable Circuit (5986).
• TSB #PIT5405C / #18-NA-161: G218 Ground Defect: Identifies a poor ground at location G218, caused by a trapped insulation mat from the factory, as a primary cause of power steering communication loss and many other electrical faults.
• GM Safety Recall #14743: Affects certain 2015 model year trucks for a defect that can cause sudden loss of power steering assist and may set code U0131. The fix is a replacement of the power steering assist motor kit, performed by a GM dealer.

Mechanic-Grade Diagnostic Values

• CAN Bus Network Resistance — expected: ~60 Ω (measured between CAN High and Low pins with battery disconnected). Failure: A reading of ~120 Ω indicates an open circuit or missing terminating resistor. A reading near 0 Ω indicates a short between the CAN wires.
• CAN Bus Voltage (Key On) — expected: CAN High: ~2.5V at rest, toggles to ~3.5V. CAN Low: ~2.5V at rest, toggles to ~1.5V.. Failure: Voltages stuck high, low, or not toggling indicate a bus fault or a module pulling the bus down.
• Communication Enable Circuit (5986) Voltage — expected: Approximately 12V (battery voltage) when the BCM is awake (Key On).. Failure: Low or no voltage indicates an open or high resistance in the circuit, often in the sill plate harness area.
• Negative Battery Cable Voltage Drop — expected: Less than 200 mV when measured from the negative battery post to the engine block while cranking the engine.. Failure: A reading above 200 mV indicates high internal resistance in the cable, requiring replacement.

Scan Tool Commands That Help

• GDS2 (GM Global Diagnostic System 2): PSCM Programming / Power Steering Control Module Setup — Required after replacing the power steering rack or control module to configure the new module to the vehicle's VIN and options.
• GDS2 (GM Global Diagnostic System 2): Steering Position/Torque Sensor Calibration — Must be performed after replacing the steering gear assembly to ensure the system has an accurate baseline for steering angle and driver input.

Wiring & Ground Locations

• G218 — Behind the driver's side dashboard end-cap trim, near the A-pillar and speaker, fastened by a 10mm nut to a metal support brace.. This is a primary ground for the Body Control Module (BCM). When faulty due to trapped insulation, it causes widespread communication codes, including U0131, because the BCM cannot properly communicate on the network.
• Sill Plate Harnesses — Running along the floor under the plastic door sill trim plates on both the driver's and passenger's sides.. These harnesses contain the CAN bus wires and the Communication Enable Circuit (5986). They are prone to chafing, moisture intrusion, and corrosion, which can sever communication to the PSCM.
• Splice J365 — Located within the wiring harness under the passenger's front door sill plate.. GM TSB #PIT5457B identifies this specific splice as a known potential point of high resistance or an open in the Communication Enable Circuit (5986), which prevents the PSCM from waking up.
• Engine Wiring Harness Junction Block — A small fuse box attached directly to the positive battery terminal in the engine bay.. This block contains the main high-amperage (80A-100A) 'Mega' fuse for the power steering system. If this fuse blows, the PSCM loses all power and cannot communicate.

Real Owner Repair Stories

• Reddit user in r/Chevy (2016 Silverado 1500 (similar K2XX platform)) — Multiple warning lights, radio turning off, gauges going haywire, similar to symptoms of a bad ground or network failure.
  ❌ Tried (didn't work) Initial thought was related to a separate recall.
  ✅ What actually fixed it The issue was diagnosed as a bad negative battery cable with high internal resistance. A technician recommended checking the voltage drop per TSB 18-NA-161, which confirmed the fault. Replacing the negative battery cable resolved the widespread electrical issues.
• YouTube channel 'DadsGarage Diagnostic Specialist' (2016 Chevrolet Malibu (similar GM electric power steering system)) — 'Service Power Steering' message, complete loss of power steering, U0131 code, and no communication with PSCM on scan tool.
  ❌ Tried (didn't work) Checking CAN bus resistance (was a perfect 60 ohms)., Checking ground at the PSCM connector (was good).
  ✅ What actually fixed it A test light and power probe revealed there was no power on the main battery feed wire at the PSCM connector. The failure was a blown main fuse for the power steering system, which cut all power to the module, making it unable to communicate.

OEM Part Supersession History

• 23412215, 84059834, 84073904, 84228166, 84346954 → 84446361 — Part revisions and updates by the manufacturer for the Power Steering Control Module, which is integrated into the steering rack assembly.
  Heads up: VIN verification is critical when ordering. This part is for the electric power steering system and should not be confused with hydraulic components on some models.

Model Year Variations Within This Range

• 2015: Certain 2015 models are covered by GM Safety Recall #14743 (NHTSA ID 14V719000) for a defect that can cause a sudden loss of power steering and set code U0131. The official fix is the replacement of the power steering assist motor kit by a dealer.