U0197 — Lost Communication with Telephone/Telematics (Hands-Free/Phone) Control Module

What it means

U0197 is a generic network DTC (second digit 0) indicating that one or more controllers stopped receiving the required messages from the telephone/telematics (hands-free) control module. Depending on platform, this module may be called TCM/TCU (telephone/telematics control module), Hands-Free Module (HFM), Uconnect/BT module, or similar. It typically resides on a body network (e.g., Ford MS-CAN ~125 kbps two-wire; GM Low-Speed GMLAN ~33.3 kbps single-wire per SAE J2411), and exchanges signals with ACM/radio, display (FDIM), BCM/gateway, IPC, and sometimes HS-CAN (~500 kbps) peers via a gateway. Ford charts explicitly show FDIM/ACM setting U0197 when phone/telematics messages are missing; FCA bulletins call it “Lost Communication with Hands-Free Phone Module.” NHTSA+3Charm+3Charm+3

Typical symptoms

  • Bluetooth/phone inoperative, no pairing; telematics (SOS/concierge/OnStar/Uconnect) inoperative
  • Radio/infotainment messages or chimes related to phone/telematics; intermittent audio-control issues
  • Global scan shows U0197 stored in FDIM/ACM/IPC/BCM; the phone/telematics module appears offline on the topology map
  • On some platforms: repeated “communication module activation failed” announcements; history U-codes after battery work or module swaps. Charm+1

Why it sets (representative OEM logic)

  • Message timeout from hands-free/phone module. A peer (often ACM or FDIM) sets U0197 when required phone/telematics messages aren’t received within a calibrated window. Ford’s pinpoint tests label U0197 as “Lost Communication With Telephone Control Module,” set by FDIM/ACM when the node is silent. Charm+1
  • OEM timer example (Mitsubishi): With IGN ON, supply OK, and bus healthy, if the radio cannot communicate with the hands-free module for ≥ 2,500 ms, it flags U0197 (CAN timeout). This is a concrete enable/threshold example. Mitsubishi Tech Info+1
  • Physical-layer issues on the body network (opens/shorts, poor grounds/low voltage, a node entering error-passive/bus-off) prevent the phone/telematics frames from reaching peers. (Where HS-CAN is involved, the backbone normally measures ~60 Ω ±5 Ω key-off; MS-CAN is similar; single-wire GMLAN uses different checks—see Diagnostics.) RepairPal.com

Common root causes

  1. Power/ground loss at the phone/telematics module (blown fuse, poor ground, low system voltage) RepairPal.com
  2. Body-network wiring faults on the path between module ↔ ACM/FDIM/BCM (opens/shorts, water intrusion, pin tension issues) Charm
  3. Gateway or termination/bias faults on the low-speed network (splice packs/star points; incorrect bias on single-wire GMLAN) RepairPal.com
  4. Internal failure of the hands-free/telematics module (e.g., transceiver fault, software requiring update) — FCA GM documents address module software updates for communication issues NHTSA+1
  5. Aftermarket device interference (amplifiers/trackers/remote starts) disturbing body/HS networks or radio feeds
  6. Collision/trim work disturbing console/A-pillar/rocker harnesses where these modules typically live

Professional diagnostics (step-by-step)

Network overview & scan strategy

  • Run a global scan and save a report. Note every U-code and which modules are offline. Use the scan tool’s topology/gateway view to see if the phone/telematics module is present and which peer (ACM/FDIM/IPC/BCM) set U0197. Ford charts explicitly tie U0197 to FDIM/ACM missing messages. Charm+1

Power/ground checks at the phone/telematics module

  • At the module connector, verify B+, IGN feed, and grounds under load (target ground drop ≤100–200 mV). A powered-down phone/telematics module will present as “lost comms” to ACM/FDIM. Correct any feed/ground issues first. RepairPal.com

Bus integrity — match the physical layer

  • Ford MS-CAN (two-wire, ~125 kbps): At the appropriate MS-CAN breakout (often not the DLC), expect ~60 Ω key-off (two 120-Ω terminators). Key-on at rest, bias ~2.5 V with small opposite deviations on H/L. Follow Ford pinpoint tests for U0197 at FDIM/ACM. Charm
  • GM Low-Speed GMLAN (single-wire, ~33.3 kbps, J2411): Do not expect “60-ohm pair.” This bus toggles 0–5 V on one conductor with distributed termination; use OEM bias/load and splice-pack isolation procedures rather than HS-CAN resistance checks. RepairPal.com
  • HS-CAN checks (if the gateway is also unhappy): Across DLC pins 6 & 14 key-off, expect ~60 Ω ±5 Ω. Out-of-spec readings indicate open/short/extra terminator on the backbone that can indirectly affect the body net via the gateway. RepairPal.com

Signal/timeout verification (if available)

  • On platforms that expose timers/counters, observe whether the reporting module (e.g., ACM) flags message timeouts ~2.5 s (Mitsubishi example) or similar before the DTC sets. This can help distinguish bus loss vs. module power loss. Mitsubishi Tech Info

Segment isolation

  • Unplug branches or pull fuses feeding body-net nodes (radio/FDIM/phone module) one at a time while monitoring when communication returns and U0197 stops resetting. For GM, isolate at splice packs; for Ford, follow pinpoint AL (information & entertainment) procedures. Charm

Connector/terminal & harness inspection (console/center-stack first)

  • Perform pin-drag tests; inspect connectors behind the radio/HVAC stack and in the A-pillar/rocker areas for water/corrosion, backed-out pins, prior audio/telematics splices, and harness chafe. Repair/repin; restore proper routing/twist where applicable. NHTSA

Aftermarket device audit

  • Temporarily remove DLC dongles, trackers, remote starts, audio integrations tied to the body/HS networks or to radio power. Retest. (Numerous OEM bulletins attribute comms clusters and infotainment faults to add-ons.) NHTSA

Module software & replacement (last)

  • Check for software updates addressing phone/telematics communication (e.g., FCA hands-free module updates; GM telematics updates related to network/timeouts). Only after wiring/grounds/bus are proven good should you reprogram or replace/initialize the module. NHTSA+1

Verified fixes

  • Restore module power/grounds (fuses, cleaned ground eyelets, corrected low voltage)
  • Repair body-network wiring (opens/shorts), clean/repin corroded connectors; seal water ingress
  • Correct termination/bias or gateway faults on the body network; verify HS-CAN backbone health when implicated
  • Remove/rewire interfering aftermarket devices
  • Update software for hands-free/telematics/ACM per OEM bulletins; replace/initialize the phone/telematics module only after network integrity is confirmed
  • Clear codes, perform a drive cycle, and re-scan to confirm.

Sources

  • OBD-Codes – U0197 (Lost Communication With Telephone Control Module) — canonical generic definition and network context. OBD-Codes.com
  • RepairPal – U0197 — plain-language definition, symptom/diagnosis framing. RepairPal.com
  • Ford OEM (charm.li mirror) — U0197/U0197:00 Pinpoint Tests — shows FDIM/ACM as the reporting modules when phone/telematics messages are missing. Charm+1
  • Mitsubishi OEM SI — “DTC U0197: Hands-Free Module CAN Timeout” — 2,500 ms message-loss threshold; enable criteria and radio-sets-U0197 logic. Mitsubishi Tech Info+1
  • FCA (NHTSA) — Uconnect/Hands-Free Module bulletins — U0197 present with HFM issues; remediation via software updates and diagnostic flow. NHTSA+1
  • GM (NHTSA) — Telematics/OnStar service information — module update procedures and programming cautions for telematics communication concerns (context for TCU-related comm faults). OEMDTC+1