U0204

Code

Generic U — Network/User

Lost Communication With Door Control Module F

Brand: Generic

Type: U — Network/User

Views: UK: 32 EN: 59 RU: 31

AI status

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Page language: EN

Causes

Open or short in CAN wiring between DCM F and network/gateway
Corroded, loose or damaged connector at the door control module or gateway
Blown fuse or lost power supply to the door control module
Bad ground at the door or body control ground point
Door control module internal failure
Gateway/BCM or other network module failure interfering with messages

Symptoms

Door functions (locks, windows, mirror fold, courtesy lights) inoperative or intermittent
Relevant door functions controlled by DCM F do not respond to switches or remote commands
One or more other modules report loss of messages from DCM F
Driver information messages or warnings about door module communication
Intermittent operation that changes with door position or vibration

What to check

Read freeze frame/occurrence count and full network DTC list with a capable scan tool
Attempt direct communication with Door Control Module F using a diagnostic tool
Verify vehicle battery voltage is stable (12V+) and fuses for door module are intact
Visually inspect door harness and module connector for corrosion, water intrusion, broken wires, or pin damage
Check for aftermarket equipment connected to the CAN or power circuits
Backprobe power and ground at the door module connector; verify key-on battery voltage and a good ground

Signal parameters

CAN bus idle voltages: CAN H ≈ 2.5 V and CAN L ≈ 2.5 V (each relative to chassis)
Dominant bus differential during activity: typically ~1.5–2.5 V between CAN H and CAN L
Termination resistance across CAN H-L (ignition off): approx. 60 ohms (two 120 ohm terminators in parallel)
Supply voltage to module: battery voltage (~12 V) with key on
Bus data rate varies by vehicle (commonly 125 kb/s or 500 kb/s); verify factory spec for the vehicle

Diagnostic algorithm

Confirm U0204 on scan tool, note occurrence, freeze frame and related U-codes. Attempt to communicate with DCM F via scan tool.
Check vehicle battery voltage and fuses for the door control module and gateway/BCM. Replace blown fuses and re-test.
Inspect door harness and module connector for physical damage, corrosion, water ingress or pin damage. Repair or replace as needed.
With connector connected, backprobe module power pin and ground pin: verify battery voltage present and a low-resistance ground with ignition on.
Measure CAN H and CAN L voltages at the DCM F connector and at the gateway/BCM. Compare values to known-good specs. Check for shorts to B+ or ground.
With ignition off, measure resistance across CAN H-L at module connector; expect ~60 ohms. If open or far from spec, trace wiring and locate open/short or missing terminator.
Perform wiggle/door-motion test while monitoring communication to find intermittent breaks in the harness inside the door jamb.
If wiring and power/grounds are good but no communication, attempt to communicate with DCM F from a known-good port (different scanner or access point) and try a module wake or reset procedure per manufacturer.
Check for other modules on same CAN reporting communications or errors (gateway fault could block messages). Swap gateway/BCM only after confirming it is the root cause.
If module fails to respond and wiring/power are verified, consider reflashing or replacing the door control module. After any repair, clear codes and retest vehicle operation and bus communication.

Likely causes

Broken or damaged CAN wires in door harness from repeated door movement or door jamb damage
Corroded or water-damaged door module connector
Failed or unpowered door control module (fuse, supply, or ground)
Gateway/BCM not forwarding messages due to internal fault or reflash needed