Faulty passenger door open switch (plunger or proximity type) that has failed internally or is stuck.; Damaged or corroded wiring in the passenger door jamb harness, often due to flexing or water intrusion.; Loose or corroded electrical connector at the switch or at the BCM.; Blown fuse or poor ground connection for the switch circuit.; BCM software glitch or internal fault causing false detection (less common).; Aftermarket accessories or previous repairs that tapped into the door switch circuit incorrectly.

DTC codes / B05xx · Airbags, seats, doors, lights and comfort systems / B0520

B0520Passenger Door Open Switch

Q: What does code B0520 mean?

Passenger Door Open Switch. B0520 indicates that the body control module (BCM) has detected a fault in the passenger door open switch circuit, meaning the switch is not reporting the correct open or closed state. The computer monitors the switch input and sets this code when the voltage or signal is outside the expected range for the door's position.

B0520 indicates that the body control module (BCM) has detected a fault in the passenger door open switch circuit, meaning the switch is not reporting the correct open or closed state. The computer monitors the switch input and sets this code when the voltage or signal is outside the expected range for the door's position.

SystemBody

Code typeGeneric (all makes)

SeverityLow

Fix difficultyIntermediate

AreaAirbags, seats, doors, lights and comfort systems

Symptoms you may notice

The passenger door open warning light stays on constantly or never illuminates when the door is opened.
The dome light or courtesy lamp fails to turn on when the passenger door is opened, or stays on after closing.
The vehicle may not detect the passenger door as open, so the key-in-ignition chime or door-ajar warning does not sound.
Power door locks or windows on the passenger side may behave erratically if the BCM uses the switch input for other functions.
Often no symptoms besides the warning light, especially if the switch is only intermittently faulty.

Common causes, most likely first

Faulty passenger door open switch (plunger or proximity type) that has failed internally or is stuck.
Damaged or corroded wiring in the passenger door jamb harness, often due to flexing or water intrusion.
Loose or corroded electrical connector at the switch or at the BCM.
Blown fuse or poor ground connection for the switch circuit.
BCM software glitch or internal fault causing false detection (less common).
Aftermarket accessories or previous repairs that tapped into the door switch circuit incorrectly.

How to diagnose and fix it

Verify the code with a scan tool and check for any related body codes in the BCM.
Inspect the passenger door open switch for physical damage, sticking, or misalignment; clean or adjust as needed.
Check the wiring harness in the door jamb for chafed, broken, or corroded wires; repair or replace damaged sections.
Test the switch continuity with a multimeter while opening and closing the door; replace the switch if it does not change state correctly.
Check the connector at the switch and at the BCM for tightness and corrosion; clean and reseat as necessary.
Check the fuse and ground for the circuit; repair any open or high-resistance connections.
Clear the code and test the system; if the code returns, consult factory service information for BCM diagnostics.

Before you replace the door switch

A common oversight is assuming the switch is bad when the real problem is a broken wire inside the flexible door jamb boot, which flexes every time the door is used.
The passenger door open switch often shares a ground with other door switches; a single bad ground can set multiple door codes, so check grounds before condemning individual switches.
On some vehicles, the BCM learns the door switch state and may need a relearn procedure after replacement, which is not always obvious from generic scan tool instructions.
Intermittent B0520 codes can be caused by water intrusion into the door connector, leading to corrosion that only acts up in damp weather.
The code does not always mean the switch itself is faulty; the BCM may set it if it sees an implausible signal due to a short to voltage or ground in the wiring.

Can I keep driving with B0520?

This fault is not safety-critical and you can continue driving, but be aware that the passenger door may not be detected as open, so the warning chime or interior lights may not work as expected. Avoid relying on the door-ajar warning until the fault is repaired.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.