U0184 — Lost Communication with Radio / Audio Control Module (ACM)

What it means

U0184 is a generic network DTC (second digit 0) meaning one or more controllers stopped receiving required messages from the radio/Audio Control Module (ACM). The radio typically lives on a body network:

  • Ford: MS-CAN (~125 kbps, two-wire); peers include APIM/SYNC (telematics), FDIM/FCIM (display/controls), BCM (gateway), IPC. Ford pinpoint tests note U0184 is logged by FDIM/APIM when ACM messages are missing. Charm+1
  • GM: Low-Speed GMLAN (~33.3 kbps, single-wire SAE J2411) with a gateway to HS-CAN (~500 kbps); multiple modules may store U0184 when the radio is offline. NHTSA
  • FCA (Jeep/Dodge/Ram): on the CAN-IHS / Audio-Telematics (AT) bus, service info describes U0184 when radio bus messages are not received ~2–5 s. Charm
  • Mitsubishi: documented as “Audio CAN timeout” between audio unit and other modules (e.g., ETACS/KOS-ECU). Mitsubishi Tech Info

Typical symptoms

  • Radio/infotainment inoperative or intermittent (no audio, blank display, no wake-up)
  • Bluetooth/phone integration unavailable; steering-wheel audio buttons inop
  • Cluster/infotainment messages; global scan shows U0184 in APIM/FDIM/IPC/BCM, with the ACM offline on topology
  • After battery service or transit mode: U0184 may appear as history until the radio wakes/responds. NHTSA

Why it sets (representative OEM logic)

  • Message timeout from ACM: A peer (FDIM/APIM/IPC/BCM) doesn’t receive ACM status frames within a calibrated timer. Ford specifies “missing ACM messages for >5 s”; Jeep charts say “bus messages not received from Radio for ~2–5 s.” Charm+2Charm+2
  • Bus/module state: If the radio is not awake, locked, or stuck during programming, multiple modules may store U0184 with no comms to radio until it cycles or is reprogrammed. GM 16-NA-107 highlights this behavior during SPS updates. NHTSA
  • OEM variation: Mitsubishi frames U0184 as Audio CAN timeout flagged by body controllers when audio signals aren’t received over the body CAN. Mitsubishi Tech Info

Common root causes

  1. Power/ground loss at the radio/ACM (blown fuse, poor ground, transport mode/lockout) NHTSA
  2. Body-network wiring faults (opens/shorts, poor pin tension/corrosion) between ACM ↔ display/BCM/gateway
  3. Gateway/body-bus issues (MS-CAN faults; single-wire Low-Speed GMLAN bias/termination faults; FCA IHS/AT bus connector/terminal spread) NHTSA
  4. Internal ACM failure (radio transceiver/software) or incomplete programming event NHTSA
  5. Aftermarket audio/telematics installs causing network noise or incorrect wake/can-lines splices

Professional diagnostics (step-by-step)

Network overview & scan strategy

  • Perform a global scan and review the topology/gateway map. Identify which module(s) set U0184 (often FDIM/APIM/IPC/BCM) and confirm whether the ACM communicates. If radio is dark and other nodes are healthy, start with power/ground and ACM wake/locks. Charm

Power/ground checks at the ACM

  • Verify B+ (battery), IGN, and grounds under load (target ground drop ≤100–200 mV). Clear codes and retest after correcting any feed/ground faults. On Ford, also ensure transport mode is disabled if present. NHTSA

Bus integrity — match the physical layer

  • Ford MS-CAN (two-wire, ~125 kbps): At the correct MS-CAN access (often not DLC), key-off expect ~60 Ω (two 120-Ω terminators). Key-on at rest ~2.5 V common-mode with small opposite deviations on H/L. U0184 is set by FDIM/APIM when ACM messages missing >5 s; follow the U0184 pinpoint test. Charm+1
  • GM Low-Speed GMLAN (single-wire, ~33.3 kbps): Do not expect a 60-Ω pair; check 0–5 V signaling and splice-pack/star-point integrity. If multiple modules show U0184 with no ACM comms, cycle the radio and update SPS per 16-NA-107 / PIT docs. NHTSA
  • FCA CAN-IHS / AT bus: Inspect SGW ↔ radio connectors for spread/pushed-out terminals when U0184 is stored; if active, continue with service-library CAN-IHS diagnostics. NHTSA

Signal/timeout verification

  • Using the reporting module (e.g., FDIM/APIM), watch message counters and verify the >5 s (Ford) or ~2–5 s (FCA) timeout before U0184 sets to distinguish bus loss from ACM power loss. Charm+1

Segment isolation

  • Depower/unplug branches (radio, amplifier, display head, telematics) one at a time or pull fuses while monitoring when the network recovers and the ACM reappears. For GM, follow radio PI/TSB steps to cycle and reflash if comms return. NHTSA

Connector/terminal & harness inspection (center stack first)

  • Perform pin-drag tests at ACM, display, and junctions; check for water/corrosion, pushed-out pins, prior audio/telematics splices, and harness chafe in the IP/console/A-pillar areas. Repair and restore routing/twist (for two-wire CAN). NHTSA

Module software & replacement (last)

  • If wiring/bus/power are good and the ACM stays offline, apply software updates; then replace/initialize the ACM per OEM programming. GM bulletins explicitly warn U0184 may persist until radio SPS completes or the unit is power-cycled. NHTSA

Verified fixes

  • Restore ACM power/grounds; disable transport mode where applicable NHTSA
  • Repair body-bus wiring (opens/shorts), fix connector pin tension/corrosion; correct IHS/AT bus terminal spread at SGW/radio NHTSA
  • For GM: power-cycle and update/reprogram radio (SPS) per 16-NA-107/PIT; verify comms after update NHTSA
  • Remove/rewire interfering aftermarket audio/telematics devices
  • Replace/initialize ACM only after proving network/power integrity
  • Clear codes, perform an operate cycle (key/audio), and re-scan to confirm.

Sources

  • OBD-Codes — U0184 (Lost Communication with Radio) — canonical generic definition and diagnostic framing. OBD-Codes.com
  • Ford OEM Pinpoint Tests (charm.li) — U0184 set by FDIM/APIM when ACM messages missing >5 s; MS-CAN diagnostic steps. Charm+1
  • FCA Case S2208000124 (2022) — U0184 stored/active guidance; CAN-IHS/Audio-Telematics bus terminal spread checks at SGW/radio. NHTSA
  • GM 16-NA-107 (2016) — Radio Inoperative/No Communication & U0184; SPS programming cautions, power-cycle/update to restore comms. NHTSA
  • Mitsubishi OEM (TechInfo) — U0184 Audio CAN timeout (audio signals not received; diagnose CAN lines). Mitsubishi Tech Info
  • Jeep/Chrysler OEM chart (charm.li) — U0184 description with ~2–5 s message-loss window and basic bus causes. Charm