U0263

Code

Generic U — Network/User

Lost Communication With Speech Recognition Module

Brand: Generic

Type: U — Network/User

Views: UK: 37 EN: 51 RU: 23

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Page language: EN

Causes

Speech Recognition Module failure (internal fault)
Loss of power or ground to the SRM (blown fuse, open circuit)
Broken, shorted, or intermittent wiring or connector to the SRM
CAN/LIN network fault (shorts, opens, high resistance, termination issues)
Module not programmed or software/firmware mismatch after replacement
Gateway/telecommunications/infotainment module fault preventing routing

Symptoms

Voice recognition or hands-free voice commands not working
Infotainment displays or menus show "Speech Recognition Unavailable" or similar
One or more communication-related DTCs present (U-codes)
Loss of features that rely on SRM (voice dialing, voice navigation input)
Possible no SRM node shown on network scanner/node list
Intermittent operation of voice features (if wiring is intermittent)

What to check

Verify customer complaint and whether the fault is current, intermittent, or historic
Read all stored DTCs and freeze frame data from all modules (note other U-codes)
Confirm SRM appears in the diagnostic tool's network node list and check responses
Check SRM fuse(s), power and ground circuits for correct voltage and continuity
Visually inspect SRM connector and wiring harness for damage, corrosion, or water
Backprobe SRM power/ground pins; measure battery voltage with key on and cranking

Signal parameters

CAN bus nominal idle voltages (recessive): CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V
CAN bus dominant state typical voltages: CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V (differential ≈ 2 V)
Typical CAN bus speeds: 500 kb/s or 250 kb/s (verify vehicle-specific bus speed)
Expected bus termination: ~60 ohm each leg to 12 V/ground when combined ≈ 120 ohm across CAN_H/CAN_L
SRM should respond to diagnostic requests within a few hundred ms; periodic messages often every 10–100 ms
No unexpected DC shorts to battery or ground on CAN_H or CAN_L

Diagnostic algorithm

Connect a qualified scan tool. Verify U0263 is current or historic and capture freeze frame/related codes. Note other communication DTCs.
Confirm the SRM is listed on the network/node list. If it is present, request ECU information (part number, software) and attempt a session. Record any response or lack thereof.
Check SRM power and ground: verify fuses, measure battery voltage at the module connector with key ON and during crank. Repair any open circuits or bad grounds.
Visually inspect the SRM connector, pins, and harness for damage, corrosion, water intrusion, or poor pin contact. Repair or replace as required.
Verify CAN bus integrity: measure CAN_H and CAN_L at the SRM connector with key ON. Confirm idle voltages, dominant voltages, and measure DC resistance across CAN_H/L (≈120 ohm).
If possible use an oscilloscope or bus analyzer to view traffic and verify SRM messages. Look for missing messages or bus errors (bit stuffing, ACK errors).
Perform a wiggle test on the SRM wiring while monitoring network traffic to detect intermittent opens/shorts.
Inspect and test other modules on the same bus (gateway, infotainment, telematics). A faulting gateway can block communication; check its DTCs and operation.
If wiring and power/ground are good but the SRM does not respond, try reinitializing power (disconnect battery per manufacturer procedure) then re-scan. If still unresponsive, consider reprogramming or swapping with a known-good SRM (only if allowed and correctly programmed).
After repairs, clear DTCs and perform a function test and road test to verify fault does not return. If DTC recurs, escalate to module-level bench testing or manufacturer-level diagnostics.

Likely causes

Blown fuse or lost power/ground specific to the SRM
Damaged CAN bus wiring (pinch, chafe, water intrusion) between SRM and gateway
Faulty SRM (no response to diagnostic requests)
Intermittent connector or poor mating causing intermittent comms
Network termination resistor missing or high resistance on CAN
Aftermarket audio or telematics equipment interfering with the bus

Fault status

⚠️ Status

Lost Communication With Speech Recognition Module — the module is not responding on the vehicle data network. Voice recognition features may be disabled until communication is restored.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0 - 3.0 hours