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U0221 — Lost Communication Door Switch G

Generic OBD-II · all makesNetwork / communication

OBD-II code U0221 indicates that the vehicle's powertrain control module (PCM) or body control module (BCM) has lost communication with the door switch module on the Controller Area Network (CAN) bus. This typically means the module is not sending or receiving expected data, disrupting related systems like interior lighting or security features.

Symptoms

What causes it — most likely first

1. Faulty door switch or module

The door switch or its integrated module may have failed internally, preventing proper signal transmission on the CAN bus. Corrosion or physical damage to the switch is common.

2. Wiring or connector issues

Damaged, corroded, or loose wiring/connectors between the door switch/module and the CAN bus can interrupt communication. Common in door hinges or harness flex points.

3. Blown fuse or relay

A blown fuse or faulty relay supplying power to the door switch module can cause a loss of communication. Check the fuse box for related circuits.

4. CAN bus network problems

Shorts, opens, or high resistance in the CAN bus wiring (e.g., between modules) can disrupt communication. This may affect multiple modules, not just the door switch.

5. Software or configuration issue

A software glitch in the door switch module or BCM/PCM may cause communication failures. Reprogramming or resetting the module may be required.

6. Faulty BCM or PCM (rare)

While uncommon, a failure in the body control module (BCM) or powertrain control module (PCM) could prevent proper communication with the door switch. This is typically a last-resort diagnosis.

How it's diagnosed

  1. Scan for additional codes in the BCM, PCM, and other modules to identify if multiple communication issues exist.
  2. Inspect the door switch and its wiring/connectors for physical damage, corrosion, or loose connections. Focus on the door hinge area and harness flex points.
  3. Check the fuse and relay supplying power to the door switch module. Replace if blown or faulty.
  4. Use a multimeter to test for proper voltage and ground at the door switch/module connector. Verify CAN bus signal integrity with an oscilloscope if available.
  5. Test the door switch/module for proper operation. Replace if it fails bench testing or does not respond to door open/close cycles.
  6. If all other causes are ruled out, consider reprogramming the door switch module or BCM. Only replace the BCM/PCM if absolutely necessary and after thorough testing.

Code facts & related codes

SystemNetwork / communication
StandardizationSAE generic — identical on every make
Related codesU0219 — Lost Communication Door Switch EU0220 — Lost Communication Door Switch FU0222 — Lost Communication Door Window MotorU0223 — Lost Communication Door Window Motor BU0224 — Lost Communication Door Window Motor CU0225 — Lost Communication Door Window Motor D

Frequently asked

Is the PCM usually the cause of U0221?

No. The PCM is rarely the cause of U0221. The issue is almost always related to the door switch itself, wiring, or the CAN bus network. Replacing the PCM should be a last resort after all other possibilities are exhausted.

Can I drive with U0221 set?

Yes, the vehicle is typically drivable, but you may experience issues with interior lighting, door locks, or security systems. Address the problem promptly to avoid further electrical system complications.

Why does my door ajar light stay on even when the door is closed?

This symptom often accompanies U0221 because the door switch or its communication with the BCM/PCM is disrupted. The system may default to an 'open' state, keeping the warning light illuminated.

Do I need a scan tool to diagnose U0221?

A scan tool is highly recommended to confirm the code, check for additional codes, and monitor live data. However, basic checks like inspecting fuses, wiring, and connectors can be done without one.