U0131 on 2015-2017 GMC Sierra: Lost Communication With Power Steering Causes and Fixes

What's Unique About the 2015-2017 Gmc SIERRA

On this generation of GMC Sierra (K2XX platform) and its platform-mates like the Chevrolet Silverado, the U0131 code is very frequently caused by specific, well-documented electrical flaws rather than a failure of the expensive steering rack itself. General Motors has issued multiple Technical Service Bulletins (TSBs) that point technicians directly to a poor ground at location G218 and damaged wiring in the door sill plates as the primary culprits. This makes diagnosis more straightforward than on other vehicles, where a U0131 code might more commonly mean a failed module.

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, making the wheel very heavy.
• "Service Power Steering" or "Steering Assist is Reduced Drive With Care" message on the Driver Information Center (DIC).
• Illuminated warning lights for ABS, Traction Control (TCS), or StabiliTrak.
• Multiple other communication codes (U-codes) stored in various modules.
• Steering wheel jerks or kicks back when turning.
• Other seemingly unrelated electrical issues, like the radio or instrument cluster going blank, especially when turning the wheel at low speeds.

Most Likely Causes

1. Poor Ground at G218 Location 🔴 High Probability As documented in GM TSB #PIT5405C, the front dash insulator mat is often trapped between the ground's ring terminal and the vehicle body during assembly. This creates high resistance and intermittent communication failures for modules grounded at this point, including the BCM which communicates with the PSCM. This is a widely reported factory flaw.
   How to confirm: Locate ground G218 under the driver's side dashboard, attached to the A-pillar support brace, often near the speaker. Remove the A-pillar trim and side dash panel to access it. Visually inspect if the black foam insulation material is caught under the ground terminal's 10mm nut. A voltage drop test from the terminal to a clean chassis point can also confirm high resistance.
   Typical fix: Disconnect the negative battery terminal. Remove the 10mm ground nut, pull back the insulation mat, and trim it with a utility knife to create clearance around the stud. Clean the terminal eyelet and the body surface with a wire brush or emery paper to ensure a clean metal-to-metal contact, then re-secure the ground nut firmly. This often resolves the issue with no parts cost.
   Est. part cost: $0
2. Damaged Wiring Harness Under Door Sill Plates 🔴 High Probability As documented in GM TSB #PIT5457D, the wiring harness that runs along the floor under the driver and passenger door sill plates is susceptible to damage, corrosion, or open circuits from moisture ingress or foot traffic. This harness contains the 'Communication Enable' wire (Circuit 5986) which is critical for waking up the PSCM and other modules.
   How to confirm: Remove the plastic sill plates and kick panels on both the driver's and passenger's sides. Carefully peel back the carpet and inspect the wiring harness, particularly any splices (like splice J365 on the passenger side), for signs of chafing, corrosion (especially green crust), broken wires, or poorly-seated connectors.
   Typical fix: Repair the damaged section of wire. This usually involves cutting out the corroded section, soldering in a new piece of wire (of the same gauge), and protecting the repair with heat shrink tubing to seal out moisture. Ensure the harness is re-routed or taped to prevent future damage.
   Est. part cost: $5-$20
3. Low or Unstable Battery Voltage 🟡 Medium Probability The electric power steering system draws a significant amount of electrical current. A weak or failing battery, bad battery cable connections, or a faulty alternator can cause voltage drops that disrupt communication between modules, triggering code U0131. TSB #PIT5405C also points to checking battery cable connections and performing a voltage drop test on the cables.
   How to confirm: Test the battery with a multimeter or a dedicated battery tester; it should read above 12.4V with the engine off. With the engine running, the voltage should be between 13.7V and 14.7V. Inspect battery terminals and cable ends for corrosion or looseness. Check the main power steering mega fuse (often 100A-175A) in the battery fuse block.
   Typical fix: Clean battery terminals and cable ends. If the battery or alternator fails testing, it must be replaced. Ensure all cable nuts are torqued to spec (e.g., 7 Nm for terminal clamps, 15 Nm for fuse block connections).
   Est. part cost: $150-$400

Rare But Worth Checking

• Failed Power Steering Control Module (PSCM) / Steering Rack Assembly: This is a common misdiagnosis. The PSCM is integrated into the electric steering rack. It should only be considered as the cause after all wiring, ground, and power supply issues have been definitively ruled out. It is an expensive replacement and requires programming to the vehicle.
• Faulty Negative Battery Cable: Some owners have found that the main negative battery cable can develop high internal resistance, causing widespread electrical issues even if the battery and alternator test good. One owner reported this fixed the issue after the G218 ground fix was only temporary. A loaded voltage drop test on the cable (while cranking) can confirm this; a drop above 200mV indicates a bad cable.
• PSCM Calibration Error: GM issued a bulletin (18-NA-193, which superseded PIT5593B) for a calibration error where the PSCM would not allow DTCs to clear and move to history even after the root cause (like a dead battery) was fixed. This can be misleading. The fix requires a dealer to reprogram the PSCM with the latest software, after which the original fault may still need to be diagnosed if it returns.
• Chafed Engine Wiring Harness: Another known issue involves the engine wiring harness chafing on the ECM/TCM bracket, upper control arm, or shock tower bolt on the driver's side. This can short various circuits, potentially causing communication issues. TSB 21-NA-149 provides a procedure for inspecting and securing the harness.

Diagnosis Steps

1. Scan for all DTCs in all modules to see if other communication codes are present, which points towards a network-wide issue.
2. Check the battery state of charge and the charging system performance. Ensure voltage is stable and above 12.4V (engine off) and ~14V (engine on).
3. Inspect the main power steering fuse(s) (Mega Fuse, often 100A+) in the underhood/battery fuse block.
4. Locate and inspect the G218 ground under the driver's side dash. Disconnect the battery, remove the 10mm nut, ensure the insulation mat is not trapped, clean the contact surfaces to bare metal, and re-tighten.
5. Remove the driver and passenger door sill plates and inspect the wiring harness for signs of damage, corrosion, or opens as described in TSB #PIT5457D, paying close attention to Circuit 5986.
6. Perform a loaded voltage drop test on the main positive and negative battery cables to check for internal resistance. A drop over 100mV on the positive side or 200mV on the negative side indicates a bad cable.
7. If grounds and wiring are confirmed to be good, use a scan tool to check for communication with the PSCM. Check for power and ground directly at the PSCM connector on the steering rack.
8. If the PSCM has proper power and ground but still won't communicate, the module/rack assembly is likely faulty.

Parts You'll Likely Need

• Power Steering Rack and Pinion Assembly (OEM #86553003) — This is only needed if the Power Steering Control Module (PSCM), which is integrated into the rack, has failed internally. This should be the last resort after all wiring and ground issues are ruled out. Part number may vary by specific configuration (e.g., with/without enhanced towing package).
  Trusted brands: ACDelco (GM Genuine)
  OEM price range: $1200-$1900
  Aftermarket price range: $700-$1200
• Negative Battery Cable — The original cable can develop high internal resistance, causing a variety of electrical faults. If a voltage drop test fails, the cable must be replaced.
  Trusted brands: ACDelco
  OEM price range: $50-$100
  Aftermarket price range: $30-$70

Related Codes That Often Appear With This One

• U0121 — Lost Communication With Electronic Brake Control Module (EBCM). The EBCM and PSCM are on the same communication bus and are often affected by the same wiring and ground issues described in the TSBs.
• U0140 — Lost Communication With Body Control Module (BCM). This is often set when the G218 ground is faulty, as the BCM is a primary component using that ground point.
• U0077 — Chassis Expansion Bus Off. This is a general network code indicating a major fault on the chassis CAN bus, which is often caused by the wiring harness issue under the sill plates mentioned in TSB #PIT5457D.

Technical Service Bulletins (TSBs) & Recalls

• PIT5457D
• PIT5405C
• 14743
• 18-NA-193
• PIT5593B
• 21-NA-149

Platform-Specific Known Issues

• TSB #PIT5405C: Addresses a wide range of communication codes, including U0131, caused by the dash insulator mat being trapped under the G218 ground terminal, creating high resistance. Also advises checking battery cables.
• TSB #PIT5457D: Points to loss of communication with multiple modules, including the PSCM (U0131), due to an open or damaged wire (specifically Communication Enable Circuit 5986) in the harness located under the driver and passenger door sill plates.
• Safety Recall #14743 (NHTSA 14V719): Issued for some 2015 models for a sudden loss of power steering assist due to an internal EPS module fault. The remedy was to replace the power steering assist motor kit, free of charge. This recall explicitly notes that DTC U0131 may be set.
• TSB #18-NA-193 (supersedes PIT5593B): Details a PSCM calibration error that prevents DTCs from clearing to history after a fault is fixed, leading to persistent warning messages. Requires a dealer software update.