U0234

Code

Generic U — Network/User

Lost Communication With Convenience Recall Module

Brand: Generic

Type: U — Network/User

Views: UK: 26 EN: 35 RU: 30

AI status

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Page language: EN

Causes

Failed Convenience Recall Module
Open/short in module power or ground circuits
Damaged, corroded, or loose connector pins at the module
Faulty or broken CAN/LIN bus wiring between module and main network
Missing or failed bus termination resistor(s)
Blown fuse or switched power supply not present

Symptoms

DTC stored for lost communication with Convenience Recall Module (U0234)
Associated convenience features inoperable (e.g., seat/recall functions, personalized settings)
Other modules may report communication errors or degraded functionality
Possible warning messages or indicator lamps for network faults or convenience systems
Intermittent operation of related features or permanent loss until fault cleared

What to check

Verify battery voltage is within specification and stable while cranking and with accessories on
Use a diagnostic scan tool to read U0234 and any other stored network codes and module list
Inspect fuses and RELAYS for modules and network power supplies
Visually inspect the Convenience Recall Module connectors and harness for damage, corrosion, or water intrusion
Check for blown fuses or missing switched battery voltage to the module
Confirm other modules on the same bus are communicating (scan tool module list)

Signal parameters

CAN High voltage (idle): ~2.5 V (approx. half battery) or typical spec for vehicle
CAN Low voltage (idle): ~2.5 V (approx. half battery) — differential ~0 V idle, ~2 V dominant
Dominant/recessive voltage differences and expected waveform shape on scope
Resistance between CAN High and CAN Low with battery disconnected: ~60 ohms (two 120Ω terminators in parallel)
Module supply voltage (VBATT) at module power pin: battery voltage (~12.0–14.5 V)
Module ground continuity to chassis ground: near 0 ohms

Diagnostic algorithm

Record freeze frame and all current/pending U-codes. Note whether U0234 is active, pending, or historical.
Verify vehicle battery condition and charge. Low battery can cause module wake/comm failures. Re-test after battery is in spec.
Use a scan tool to verify whether the Convenience Recall Module appears in the module list. If not present, note any other modules missing.
Inspect module harness and connector for corrosion, bent pins, damage, or water intrusion. Repair or replace as needed.
Check fuses and power feeds to the module. Verify VBATT and ignition-switched power at the module connector with a DVOM.
Verify ground quality: measure resistance from module ground pin to battery negative/chassis (
With ignition ON, use an oscilloscope or CAN/LIN analyzer at the module connector to confirm network traffic and correct waveform levels. Look for expected message IDs or absence of traffic.
Measure termination resistance across CAN H and CAN L with battery disconnected. Expect ~60 ohms (vehicle-specific). Large deviation indicates missing/failed terminator.
If wiring or bus appears good but module remains unresponsive, try disconnecting any recently added aftermarket accessories or modules that share the bus.
If available, swap or bench-test the module (manufacturer procedures) or substitute a known-good unit to confirm module fault. Follow reprogramming/encoding requirements when replacing.
After repair, clear codes and perform functional test of convenience features and verify U0234 does not return during several key cycles and normal operation.
If intermittent, perform wiggle tests on harness while monitoring bus traffic and DTC status to reproduce fault.

Likely causes

Connector corrosion or bent pins at the recall module
Loss of module battery feed or ground (fuse, splice, broken wire)
Broken or shorted CAN high/low pair near module or at splice
Failed module electronics (internal processor or transceiver)
Vehicle software update/recall left module unprogrammed or incompatible

Fault status

⚠️ Status

Lost communication with Convenience Recall Module — module not responding on vehicle data bus or messages absent/invalid. Check module power, ground, connectors, and bus wiring before module replacement.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-3.5 hours

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