U0218

Code

Generic U — Network/User

Lost Communication With Door Switch D

Brand: Generic

Type: U — Network/User

Views: UK: 25 EN: 52 RU: 27

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Page language: EN

Causes

Broken, chafed, or disconnected wiring between the door switch and body control module (BCM)
Corroded or loose connector at the door, hinge, or BCM
Faulty door switch (mechanical or internal electrical failure)
Faulty or unpowered Door Switch module or Door Module
Body Control Module (BCM) or gateway module fault
CAN/LIN bus fault (short, open, incorrect termination, noise)

Symptoms

DTC U0218 stored and MIL or dash message indicating communication fault
Door open/closed status incorrect or intermittent on dash or infotainment
Interior lights, courtesy lamps or dome functions behave incorrectly
Central locking, keyless entry, or alarm functions may not respond correctly
Other modules may report related communication U-codes
Intermittent operation that changes with door position or harness movement

What to check

Read all stored and pending codes from all modules with a capable scan tool; note freeze frame and time stamps
Check for additional U‑codes or related B/C codes (power, ground, CAN bus) that can point to root cause
Visually inspect door wiring harness, door jamb grommet, connectors and BCM connectors for corrosion, damage, pin push-out or moisture
With door open/closed, operate switch and observe scan tool data for door status or Module present/missing messages
Measure power and ground at the door switch/module connector (with connector connected) for proper voltage and good ground
Check CAN/CAN‑L / CAN‑H (or LIN if applicable) voltages at multiple points (BCM, door module) and verify approximately 2.5 V idle on each line and ~60 ohm termination across differential

Signal parameters

Network: typically CAN bus (high/low differential) or local LIN for simple switches — verify vehicle-specific bus
Expected idle voltages: CANH ≈ 2.5 V, CANL ≈ 2.5 V (differential ~0 V idle); dominant state shifts as bus is driven
Message frequency: door switch/status message is usually periodic or event-driven (commonly 1–10 Hz for periodic reports; may be event on change)
Data: specific CAN ID and byte(s) contain door D open/closed status — verify with manufacturer data or a good vehicle
Termination: proper bus termination resistance across CANH/CANL should be ~60 Ω (two 120 Ω in parallel) on vehicle

Diagnostic algorithm

Connect an OBD-II diagnostic tool capable of reading body network modules. Record all codes and note related modules reporting loss of communication.
Verify vehicle-specific service information for exact module name (Door Switch D vs Door Module) and wiring/location.
Inspect door D wiring, grommet, and connectors for damage, corrosion, or water. Repair any visible damage.
With connector keyed in place, backprobe or unpin harness to measure ignition-switched and fused power to the switch/module and a solid ground. Repair faults.
Check for presence of the door switch/module message on the bus using scan tool live data. If no data, attempt a module present check or module wake-up procedure per service data.
Measure CANH/CANL (or LIN) at the door module connector and at the BCM. Verify correct idle voltage and that the bus shows activity when other modules communicate. Check termination resistance across CANH/CANL.
Perform a wiggle test on the harness with a helper operating the switch and door while monitoring for signal dropouts. Pay close attention to the harness through the door hinge area.
If the door switch is accessible, verify switch continuity/operation with a multimeter while operating it. Replace the switch if it fails.
If wiring and switch check good but communication still missing, test or swap the door module (if removable and supported) or inspect BCM/gateway for faults. Follow manufacturer procedures for programming/replacement.
After repairs, clear codes and confirm fault does not return with repeated operation of the door and road test. Recheck related modules for stored codes.