B1320 — Driver Door Ajar Circuit Open #

Please note: The wording of this code may vary depending on the vehicle manufacturer.

• Driver Door Ajar Circuit Open (Ford, Lincoln, Mercury)
• Driver’s Door Switch Circuit Open (Nissan)
• Front Left Door Ajar Switch Circuit Malfunction (Toyota)
• Driver Door Switch Signal Lost (General Motors – GM)

Summary for DTC B1320 #

B1320 is a Diagnostic Trouble Code (DTC) that indicates the vehicle’s control module has detected an “open” (broken or disconnected) circuit in the driver’s door ajar switch wiring. The door ajar switch is a simple electrical device mounted inside the door latch assembly; it informs the car’s body control module (BCM) whether the door is properly shut or not. An “open circuit” means the electrical signal isn’t reaching its destination—either due to a cut wire, unplugged connector, or faulty switch. As a result, the system may falsely “think” the driver’s door is always open or always closed, leading to warning lights, courtesy lights staying on, or security system issues. Though not as critical as engine or brake fault codes, ignoring B1320 could impact comfort, security, and even battery life.

Common Symptoms for B1320 #

When the Driver Door Ajar Circuit Open code is stored, the vehicle may exhibit several noticeable symptoms. These issues are usually more of an inconvenience than an immediate safety concern, but they can quickly become annoying or even drain your battery if left unchecked. Drivers often notice:

• Driver’s door ajar warning light stays on (even when door is closed)
• Interior/courtesy lights remain illuminated after locking
• Chime or warning sounds when driving, especially at low speeds
• Remote lock/unlock or alarm system may not function correctly
• Auto-lock feature fails to activate after driving off

Likely Causes for B1320 #

Several possible issues can trigger the B1320 code, but some are more common than others. The most frequent causes, ranked by likelihood, are:

1. Faulty driver’s door ajar switch (mechanical wear or contamination)
2. Damaged or broken wiring in the door harness (especially where wires flex near the hinge)
3. Unplugged or corroded connectors at the door latch or body control module (BCM)
4. Defective BCM (Body Control Module) (rare, but possible if all else checks out)
5. Water intrusion or rust in latch assembly

Step-by-Step Diagnostic for B1320 #

Diagnosing a B1320 code requires a methodical approach, focusing on both mechanical and electrical checks. Here’s a proven process:

• Verify the complaint: Check if the warning light or chime is active with the door closed.
• Use a scan tool: Confirm presence of B1320 and clear it; see if it returns.
• Inspect the driver’s door latch and ajar switch for physical damage or contamination.
• Wiggle-test the wiring harness as the door opens and closes; look for intermittent faults or exposed wires.
• Check connectors for corrosion, bent pins, or loose fit at the latch and BCM.
• Test switch function directly with a multimeter: Is there continuity when the door is closed?
• If all wiring and switch test fine, verify BCM input using the scan tool’s live data function.
• Consider BCM replacement only after all other possibilities are eliminated.

Possible Repairs for B1320 #

Depending on the underlying cause, the following repairs can resolve B1320:

• Replace the driver’s door ajar switch or latch assembly if faulty
• Repair or replace damaged door wiring harness (especially at the hinge area)
• Clean and reconnect corroded connectors
• Apply dielectric grease to prevent future corrosion at connections
• Replace the BCM (only after full diagnosis and if all other repairs fail)

Can You Drive With Code B1320? #

Yes, but with limitations. The B1320 code won’t disable your vehicle or cause immediate safety issues. However, persistent courtesy lights or warning chimes can be distracting, and leaving interior lights on can drain the battery. Security features or auto-lock functions may also be impaired. It’s safe for short trips, but repair should not be delayed for comfort, security, and battery health.

Vehicles Most Commonly Affected by B1320 #

While the B1320 code can appear in various makes, it’s most frequently reported on certain models, especially those using similar door latch technologies. Vehicles with a history of this issue include:

• Ford F-150, Explorer, Escape (2000s to early 2010s)
• Lincoln Navigator, MKZ
• Mercury Mountaineer
• Nissan Altima, Maxima (selected years)
• Toyota Camry, Corolla (specific trims)
• GM Silverado, Sierra (late 2000s–2010s)

Common Mistakes & Best Practices for B1320 #

Technicians and DIYers sometimes make avoidable errors with this code. To avoid wasted time and money, keep these in mind:

• Don’t replace the latch or BCM before checking wiring—broken wires at the hinge area are common!
• Always confirm the fault is in the driver’s door (not passenger or rear doors)
• Use dielectric grease after cleaning connectors to prevent repeat corrosion
• Be gentle when probing connectors to avoid bending pins
• Cycle the door open/closed several times after repair to confirm fix

Quick FAQ for B1320 #

What does ‘ajar circuit open’ mean?
It simply means the electrical circuit that tells your car if the driver’s door is open or closed is interrupted—often due to a faulty switch, broken wire, or bad connector.

Will this code affect my car’s alarm or central locking?
Yes, it can. If the system thinks the door is always open, remote lock/unlock and alarm arming may not work properly. That’s why prompt repair is recommended, even if the car runs fine.