B1335 — Door Ajar RR Circuit Failure

The diagnostic trouble code B1335 typically indicates an issue within the **Rear Right (RR) Door Ajar Circuit**, suggesting that the vehicle’s system detects a fault in the door’s warning or latch circuit. This code often appears when the vehicle’s ECU (Engine Control Unit) recognises an abnormality in the electrical signals related to the rear right door’s “ajar” (open or not fully closed) detection system.

Note: **Labelling may vary between manufacturers**. Different OEMs (Original Equipment Manufacturers) might use alternate codes or labels to refer to similar issues related to the rear right door ajar circuit. Always verify specific vehicle documentation when diagnosing.

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Manufacturer variations for trouble code B1335

Different vehicle manufacturers may label or code this issue differently, reflecting variations in their diagnostic protocols. The **B1335 code** is primarily a generic OBD-II code, but OEM-specific labels can vary. Below are some known label variations:

• Ford: U251A / U251B (depending on model, related to door circuit faults)
• Volkswagen: 5F-wards / Door Sensor Circuit – Rear Right
• BMW: 61 35 107 / Door Lock Sensor Circuit Malfunction
• Toyota: B1110 / Rear Door Ajar Sensor Circuit
• Honda: B1062 / Rear Door Ajar Switch Circuit

*Always consult the vehicle’s OEM-specific diagnostic documentation for exact labels and definitions.*

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What does trouble code B1335 mean?

In simple terms, the vehicle’s electronic system is monitoring the rear right door’s “ajar” status, which indicates whether the door is closed or not. The **ECU** (Electronic Control Unit) checks the circuit connected to the door’s latch and sensor. When the circuit detects an open or malfunctioning signal — for instance, a broken wire, faulty switch, or loose connector — it triggers the B1335 code.

This code can also occur if the sensor or switch that detects if the door is closed is faulty, or if there is an issue with the wiring harness. It’s often noticed during routine diagnostics or when warning lights appear on the dashboard.

Typically, the B1335 code appears during vehicle startup, or when opening/closing the rear right door, especially if the system is unable to correctly determine the door’s status.

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Severity and risks of trouble code B1335

The danger level associated with B1335 is generally considered **moderate**. It does not typically prevent the vehicle from being driven safely but can impact certain functions or safety features.

Potential risks include:

• Illumination of warning lights (e.g., door warning or a general warning light)
• Failure of interior lights to turn on/off as expected
• Potential security issues if the vehicle’s immobiliser or alarm system relies on door status
• Inability to use certain features designed for door status detection, such as child locks or auto-lock functions

Can the vehicle be driven? Yes, but caution is advisable. If the door remains inaccurately detected as open, it may affect safety alerts or cause inconvenience. Persistent issues should be professionally diagnosed and repaired to ensure proper vehicle function and safety compliance.

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Symptoms of trouble code B1335

Common symptoms associated with the B1335 fault include:

• Warning lights on the dashboard related to doors or vehicle body
• Interior lighting behaving irregularly — flickering or not turning on
• Door ajar warning message displayed on the instrument cluster
• The rear right door may not lock or unlock properly via central locking
• Unusual noise from the door latch area during opening or closing
• Inability to activate some safety or cosmetic vehicle features linked to door sensors

It’s also common for a technician to observe inconsistent signals or voltage levels when performing live data readings during diagnostics.

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Most likely causes of trouble code B1335

Addresses the most frequent reasons why this code may trigger, starting with the most common:

1. Faulty Door Lock or Latch Switch: The switch or latch mechanism that signals whether the door is closed may be malfunctioning or worn out.
2. Damaged Wiring or Connectors: Corrosion, broken wires, or loose connectors in the rear right door circuit can cause intermittent or no signals.
3. Faulty Body Control Module (BCM): The BCM manages various body functions, including door status detection; an internal fault might cause erroneous readings.
4. Incorrect or Intermittent Power Supply: Voltage dips or a poor ground connection can lead to false signals or circuit failure.
5. Aftermarket Modifications or Repairs: Non-original parts or repairs might compromise circuit integrity, leading to errors.

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How to diagnose trouble code B1335

When approaching diagnostic work for this code, adhere to methodical and safe procedures:

1. Perform a visual inspection: Check the rear right door latch area, wiring harness, connectors, and the switch for visible damage or corrosion.
2. Test the door switch: Use a multimeter to verify continuity and output signals when actuating the switch manually.
3. Inspect wiring continuity: Ensure wires are intact and making good connection from the door to the vehicle’s main wiring harness.
4. Check live data: Use an OBD-II scanner or a dedicated diagnostic tool to monitor the door ajar status in real time.
5. Evaluate power and ground: Verify the circuit’s supply voltage and ground connection with a multimeter, ensuring proper electrical flow.
6. Test other related components: Assess the BCM or body controller if initial tests indicate internal fault or communication issues.

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Possible repairs for trouble code B1335

The appropriate repair will depend on the diagnosed cause. Typical fixes include:

• Replacing the rear right door latch switch — this is a straightforward repair suitable for a competent DIYer or professional.
• Repairing or replacing damaged wiring or connectors — professional work may be needed to re-terminate or replace wiring harnesses.
• Reseating or replacing connectors — sometimes corrosion or loose connections can be remedied easily.
• Reprogramming or replacing the Body Control Module (BCM) — only performed by a qualified technician, often after verifying internal faults.
• Ensuring proper power and ground connections — addressing electrical supply issues to prevent false readings.

*Most repairs are considered **basic** (e.g., replacing switch or fixing wiring), but some, like BCM replacement, require professional expertise and specialised tools.*

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Vehicles commonly associated with trouble code B1335 in Europe

This code is relevant across various vehicle brands in Europe, especially in models where door sensors are integrated into advanced safety and security systems. While specific data varies, typical affected brands include:

Volkswagen Group: Volkswagen, Audi, SEAT, Škoda vehicles built in the last decade often share similar body control systems.

Ford: Various models, including Fiesta, Focus, and Mondeo, which use similar door detection systems.

BMW: Many models from the 3 Series, 5 Series, and others employing electronic door sensors.

Toyota and Honda: Specific models with electronic latch monitoring and safety interlocks.

*Always check the specific vehicle’s service documentation for details about the affected systems and known common issues.*

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Frequent mistakes with trouble code B1335

Diagnosing and repairing this issue requires attention to detail. Common mistakes include:

• Assuming the fault is solely the door switch without verifying wiring integrity
• Ignoring the importance of checking power supply and grounding before replacing parts
• Overlooking the possibility of BCM or ECU internal faults
• Performing repairs without clearing codes and verifying if the issue reappears
• Relying only on generic tools without performing live data monitoring

*Adopting a systematic approach helps avoid unnecessary replacements and ensures a durable repair.*

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FAQ — trouble code B1335

Can this code disappear on its own?

No. If the fault is genuine (such as broken wiring or faulty switch), the code will typically remain until properly repaired or replaced. Sometimes, temporary glitches can clear, but underlying issues often persist.

Can I keep driving?

Yes, in most cases, driving is still possible. However, you should monitor for warning lights, and if the rear right door warning persists or safety features are compromised, it’s wise to seek professional diagnosis promptly.

Why does the code return after clearing?

This usually indicates that the underlying cause—such as a faulty switch, wiring issue, or BCM fault—has not been addressed. The code reappears when the system retests the circuit after reset.

Always follow comprehensive diagnostic procedures to identify and fix the root cause rather than just clearing the code.