U0131 — Lost Communication with Power Steering Control Module (PSCM)

What it means

U0131 is a generic network DTC (second digit 0) indicating one or more controllers stopped receiving required messages from the Power Steering Control Module (PSCM). Communication is typically on high-speed CAN (HS-CAN ~500 kbps) (a.k.a. GMLAN High-Speed, CAN-C). Typical peers on this bus include ECM/PCM, TCM, ABS/EBCM, EPAS/PSCM, BCM, IPC/cluster, and the gateway. Most service publishers define U0131 specifically as PSCM communication loss.
OEM variation to note: many manufacturers use U0151 (not U0131) for airbag/SRS (RCM/SDM) lost communication. If your platform shows SRS loss under U0131, follow that OEM’s SI; otherwise, expect U0151 for RCM/SDM comm loss. NHTSA+3RepairPal.com+3OBD-Codes.com+3

Typical symptoms

  • Steering/EPAS warning message; reduced or no power steering assist
  • Multiple warning lamps (ABS/ESC/steering); chimes/messages; possible limp-home behavior
  • Scan tool shows U-codes across several modules; PSCM offline or intermittent on topology map
  • On some platforms, crank-no-start or stall complaints may accompany network instability (secondary effect) RepairPal.com+1

Why it sets (representative OEM logic)

  • Message timeout from PSCM: Gateway/IPC/ECM (or other supervising modules) do not receive required PSCM frames for a calibrated time window → set U0131. GM and FCA documents treat this as lost-comms, not an internal PSCM functional fault. NHTSA+1
  • Physical-layer/network degradation: HS-CAN opens/shorts, incorrect termination, or a node holding the bus dominant cause missed messages. OEM HS-LAN procedures call for ~60 Ω ± 5 Ω key-off across the HS bus (two 120-Ω terminators in parallel); <60 Ω suggests short/extra terminator; >60 Ω suggests open/missing terminator. NHTSA
  • Grounding/connector nuance: FCA identified cases where weld spatter or heat-shrink glue at a ground eyelet caused intermittent U0131 due to poor ground contact—illustrating how small ground defects can manifest as network loss. NHTSA

Common root causes (rank-ordered)

  1. Power/ground loss at the PSCM/EPAS rack (blown fuse, poor ground eyelet, low system voltage) NHTSA
  2. HS-CAN wiring faults (opens/shorts to B+/ground, CAN_H↔CAN_L short), damaged splices/junctions
  3. Termination faults (missing/failed 120-Ω end → total ≠ ~60 Ω) NHTSA
  4. Connector/pin issues at the EPAS/PSCM (pin tension, corrosion, water intrusion; rodent damage near rack) F150 Forum
  5. Internal PSCM/transceiver fault intermittently going error-passive/bus-off
  6. Aftermarket device interference (DLC dongles, trackers, remote starts) raising error rates or backfeeding the network (documented by GM) NHTSA+2NHTSA+2

Professional diagnostics (step-by-step)

Network overview & scan strategy

  • Run a global DTC scan. Note which modules store U0131 and which nodes are offline. Use your scan tool’s topology/gateway map to confirm PSCM presence and whether other HS-CAN nodes communicate normally. RepairPal.com

Power/ground checks at the PSCM and gateway

  • At the EPAS/PSCM connector: verify B+, IGN, and grounds under load (ground drop ≲100–200 mV). Inspect grounding eyelets for paint/weld spatter/heat-shrink glue; re-establish flat, clean metal-to-metal contact. NHTSA

Bus integrity tests (HS-CAN)

  • Key-off resistance: Measure between DLC pins 6 & 14. Expect ~60 Ω ± 5 Ω.
    – >60 Ω ⇒ open/missing terminator; <60 Ω ⇒ short/extra terminator. NHTSA
  • Key-on voltage/scope: At rest, HS-CAN common-mode ≈ 2.5 V with small, opposite deviations on CAN_H/CAN_L. Scope to confirm a clean differential waveform; look for stuck levels, reflections, or heavy noise (termination/ground issues or a node dragging the bus). NHTSA

Segment isolation

  • Unplug nodes/branches or pull fuses feeding sub-nets while watching for network recovery (modules reappear, comms restore). GM HS-LAN bulletins recommend a structured isolation and, where applicable, a data-bus diagnostic tool before any module replacement. NHTSA

Connector/terminal & harness inspection (EPAS area first)

  • Perform pin-drag tests; inspect for water/corrosion, backed-out pins, chafed twisted pairs, or rodent damage near the rack/left frame rail/bulkhead. Repair splices; secure routing/twist. F150 Forum

Aftermarket device audit

  • Remove or disable DLC-attached devices (insurance dongles, trackers, data loggers) and any splices to HS-CAN/power. GM documents multiple electrical/network concerns from such devices—ret test after removal. NHTSA+1

Module actions (only after bus health is proven)

  • Apply applicable software updates. If wiring/termination/power are good and PSCM remains offline, replace/initialize the PSCM per OEM programming procedures. GM and OEM guidance stresses completing HS-LAN diagnostics before parts. NHTSA

Verified fixes

  • Restore PSCM power/grounds; clean/flatten ground eyelets; correct low-voltage conditions NHTSA
  • Repair HS-CAN wiring (opens/shorts), correct splices/junctions; maintain twist/routing
  • Restore proper termination (two 120-Ω ends ≈ 60 Ω total) NHTSA
  • Clean/repin PSCM/EPAS connectors; correct pin tension; seal water-ingress paths
  • Remove/rewire interfering aftermarket DLC devices (per GM bulletins) NHTSA
  • Reflash/initialize or replace a failed PSCM/gateway only after proving network health
  • Clear codes, drive cycle, and re-scan to confirm. NHTSA

Sources

  • OBD-Codes — U0131 (Lost Communication with PSCM) — generic definition, diagnostic overview. OBD-Codes.com
  • RepairPal — U0131 — consumer-oriented but accurate definition/symptoms; aligns PSCM as the affected module. RepairPal.com
  • GM/ACDelco via NHTSA — “Diagnosing High-Speed LAN Concerns” — OEM HS-LAN method and ~60 Ω ± 5 Ω spec; isolation strategy. NHTSA
  • GM 08-07-30-021H (2015) — HS-GMLAN lost-comm bulletin; perform network diagnostics before parts. NHTSA
  • GM 13-08-116-001H (2022) — Aftermarket ALDL/DLC devices can cause multiple electrical/network concerns; remove and retest. NHTSA
  • FCA (2023) — U0131-00 Lost Communication with PSCM — ground-eyelet and weld-spatter remediation at steering rack ground, real-world cause of intermittent U0131. NHTSA
  • Context on SRS variant: OBD-Codes U0151 + GM Recall 18179 confirm U0151 (not U0131) is the common SRS/RCM/SDM lost-comms code across Ford/GM; include if the platform concern is airbag. OBD-Codes.com+1