B1573 — Door Ajar LR Circuit Short To Battery
The diagnostic trouble code B1573 indicates a problem within the **Left Rear (LR) door circuit**, specifically that there is a **short circuit to the vehicle’s battery**. Essentially, the vehicle’s **Electronic Control Unit (ECU)** has detected an abnormal electrical condition in the door’s wiring that could cause unintended electrical power flow. Note that the specific label or code terminology might vary depending on the vehicle manufacturer.
- System affected: Door circuit with switch open/closed detection
- Severity: Moderate to high, depending on voltage short circuit
- Main symptoms: Door ajar warning light, possible malfunction of door locks or windows
- Driveability: Limited — in some cases, the vehicle may still be driven, but caution is advised
Manufacturer variations for trouble code B1573
Manufacturers may assign different labels or specific code identifiers for similar issues. While the underlying problem remains consistent, the coding nomenclature can vary. Here are notable variations:
- Ford: B1573 – « Door Ajar LR Circuit Short To Battery »
- Volkswagen / Audi: 00931 – « Left Rear Door Circuit Short »
- BMW: 13A045 – « Door Circuit Open or Shorted »
- Mercedes-Benz: SRS/ADAPT Panel code, specific to door circuit faults
What does trouble code B1573 mean?
Simply put, B1573 signals that there is an electrical problem specifically within the **Left Rear (LR) door wiring**, where a **short circuit to the vehicle’s battery** has been detected. The ECU constantly monitors the **door’s electrical circuit**, including the switch that detects whether the door is open or closed.
This code is triggered when the ECU detects a **short circuit**—a direct connection—between the door’s wiring and the **positive terminal of the vehicle’s battery**. A short circuit can occur due to damaged wiring, faulty connectors, or components that have been compromised by wear, corrosion, or physical damage.
Typically, this issue appears when there is an **abnormal electrical current flow** that deviates from normal operation, often during a **diagnostic scan or when switching on the ignition**. The problem could originate from anything that causes the circuit to be permanently connected to the battery, such as a frayed wire, damaged switch, or improperly repaired wiring.
Severity and risks of trouble code B1573
This code indicates a **moderate to potentially serious electrical short**. If left unaddressed, a short circuit to the battery can cause several risks. Over time, it may lead to **battery drain**, **blown fuses**, or **damage to electrical components** associated with the door or the vehicle’s comfort systems.
In terms of risks, the most significant concern is that electrical components (such as power windows, central locking, or interior lighting) could malfunction. Additionally, a persistent electrical short could, over time, damage wiring insulation or cause overheating, which could be a fire hazard in extreme cases.
**Can the vehicle be driven?** — Yes, but with caution. In some situations, the vehicle can still operate, but driving with unresolved electrical issues is not recommended. It is best to diagnose and repair the problem promptly to avoid further damage or inconvenience.
Symptoms of trouble code B1573
When this fault is present, a vehicle owner or technician might notice the following symptoms:
- Warning light: The **door ajar warning light** appears on the dashboard, even when the door is properly closed.
- Door lock or window issues: Malfunction in the **power window or central locking system** on the rear door.
- Intermittent electrical performance: Fluctuating operation of door-related components, such as sensors or switches.
- Unusual sounds or smoke: In rare cases, electrical arcing or burning smells if the short circuit worsens.
- Persistent fault code: Diagnostic scan tools display B1573 during fault detection.
Most likely causes of trouble code B1573
This fault typically occurs due to issues within the **door’s electrical circuit**, often stemming from physical or electrical damage. Here are the most common causes, ranked from most to least probable:
- Wires running to the left rear door are frayed, cut, or have degraded insulation, causing a short circuit to the vehicle’s battery.
- Faulty door switch or sensor: The switch that detects whether the door is open or closed is malfunctioning or internally shorted.
- Corrosion or debris in connectors: Moisture or dirt accumulation in connectors or pin terminals may cause bridging that leads to a short circuit.
- Damaged or defective control module: Less common, but possible, where the door control module or related ECU component is failing or internally damaged.
- Improper repair or previous wiringwork: Poor-quality repairs or modifications could introduce shorts or poor connections.
How to diagnose trouble code B1573
Before making repairs, a systematic diagnostic approach can help pinpoint the exact cause of the fault. Here are the generic steps:
- Visual inspection: Carefully examine wiring harnesses, connectors, and the door panel for visible damage, corrosion, or loose connections.
- Check fuses and relays: Verify that all relevant fuses are intact and that relays associated with door circuits are functioning correctly.
- Test wiring continuity: Use a multimeter to check for continuity in the wiring from the body control module to the door switch and motor, looking for shorts or opens.
- Inspect the door switch: Remove and test the switch for proper operation and signs of internal damage or shorting.
- Perform live data monitoring: Use a scan tool to observe the door switch signals live when opening and closing the door, checking for abnormal voltage or resistance values.
- Check for abnormal voltage: Measure voltage at various points in the circuit to identify where a short might occur to the battery.
Possible repairs for trouble code B1573
Repair strategies focus on eliminating the suspected cause of the short circuit. Here are some potential repairs, categorized by cause, along with recommendations on whether they are simple or require professional intervention:
- Replace damaged wiring or insulation: If wiring is frayed or broken, repair or replace the affected wires. Professional repair recommended.
- Replace faulty door switch: Install a new switch if the current one tests as defective. Basic repair, suitable for DIY with proper tools.
- Clean or replace connectors: Remove corrosion and ensure solid pin contacts, or replace connectors if damage is extensive. Basic to intermediate repair.
- Repair or replace control modules: If the ECU or door control module is internally damaged, professional replacement or reprogramming may be necessary.
- Ensure correct wiring rear configurations: Repair or replace wiring harnesses after confirming the cause of the short. Professional diagnosis and repair preferred.
Vehicles commonly associated with trouble code B1573 in Europe
Since this fault pertains specifically to a door circuit, many vehicle makes with **rear door electrical systems** are affected. In Europe, typical brands include:
Volkswagen Group (VW, Audi, Škoda, Seat): These vehicles often share wiring architecture for rear door modules.
BMW: Certain models with rear power window or central locking systems may display this code.
Mercedes-Benz: Some models with advanced door sensors or central locking systems report similar codes.
Ford: Specific models with rear door electronic controls or sensors could show related faults.
Frequent mistakes with trouble code B1573
Proper diagnosis requires attention to detail. Common mistakes include:
- Overlooking visual damage: Ignoring obvious wiring or connector damage during inspection can lead to misdiagnosis.
- Replacing components prematurely: Replacing control modules or switches without confirming the short circuit can result in unnecessary repairs.
- Ignoring related circuits: Focusing solely on the door switch without checking the entire wiring harness or associated relays may miss the root cause.
- Neglecting fuse testing: Not verifying fuse integrity can overlook a blown fuse that causes the fault.
- Failing to clear codes properly: Not clearing existing codes after repairs or not performing a road test can result in phantom faults reappearing.
FAQ — trouble code B1573
Can this code disappear on its own? — While some electrical faults may temporarily resolve, a short circuit to the battery usually persists until repaired. Relying on it disappearing spontaneously is not recommended. Proper diagnosis is necessary to prevent further damage.
Can I keep driving? — Yes, in some cases, the vehicle can be driven, but the electrical fault may cause other issues over time. It is advisable to address the problem promptly.
Why does the code return after clearing it? — The underlying cause, such as damaged wiring or a faulty switch, remains uncorrected. Following repairs, if the fault persists, it will likely trigger the code again.