U0221: Lost Communication With Door Switch G
What to do
The vehicle drives normally.
The first question is whether anything is actually wrong. A real door switch fault shows itself — an interior light that will not go out, a battery going flat, an alarm that will not set, a door-open warning that is wrong. If there is no symptom at all and nobody can work out which door this refers to, it is very likely a configuration issue rather than a fault: bodies built to order often use a control unit set up for more doors than the vehicle actually has, and it reports the missing ones for ever.
That is a coding correction, not a repair, and no amount of wiring inspection will find it.
If there is a symptom, you can usually find the door yourself: in a dark garage, open every door, tailgate and panel in turn and watch for the interior light or the display reacting. The one that produces no reaction is the one at fault.
What this code means
The seventh door switch has stopped being heard from. See U0215 for the family's framing.
This is the last of the door switch series, and as at U0205 the practical advice is that documentation beats deduction. On a vehicle with seven addressable door switches the letter-to-door mapping is manufacturer- or converter-specific with no convention to fall back on, and the physical identification method at U0216 — opening each opening in turn and watching the vehicle's reaction — is often faster than finding the diagram, because it requires nothing but the vehicle itself.
The configuration point from U0205 applies with even more force at the end of a series. Bodies built to order commonly use a control unit expecting the full complement of doors, fitted to a vehicle that has fewer. A permanent lost-communication code for the highest-numbered switch, present since the vehicle was new and never accompanied by any symptom, is very often equipment that does not exist rather than equipment that has failed.
The distinguishing question is whether there is a symptom at all. A door switch fault that is real produces something a person notices — an interior light behaving oddly, a battery going flat, an alarm that will not set. A code with no symptom whatsoever, on a vehicle where nobody can identify which door it refers to, is a configuration matter, and chasing it as a wiring fault wastes a great deal of time.
Likely causes
Start here
- Module not coded to the vehicle · specialist
- Corroded or loose connector · easy
- Damaged wiring harness · moderate
Less common
- Water ingress into the module connector · moderate
Symptoms
Components involved
Information, not instruction
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Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
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