Introduction:
The B1573 diagnostic trouble code (DTC) indicates a problem within the door ajar circuit, specifically a short to the battery voltage on the left rear (LR) door. This means that the door ajar sensor or the wiring associated with it is experiencing an unintended electrical connection to the vehicle's positive (battery) voltage. This can cause various issues, from a constantly illuminated door ajar warning light to potentially draining the battery. Diagnosing and repairing this issue promptly is crucial for maintaining the vehicle's electrical system integrity and preventing further complications.
Table: B1573 Door Ajar LR Circuit Short To Battery Details
| Topic | Description | Potential Causes of the legislation, regulations, or relevant legal frameworks. TOYOTA. | Component | Description | Potential Issues |
|---|---|---|---|---|---|
| Door Ajar Switch (Left Rear) | A small switch located on the door jamb that signals to the body control module (BCM) when the door is open or closed. | Faulty switch: The switch itself may be defective, not making proper contact when the door is closed. Corrosion: Corrosion on the switch terminals or wiring can cause a short. * Physical damage: The switch could be physically damaged, leading to an internal short. | |||
| Wiring Harness | The bundle of wires connecting the door ajar switch to the BCM. This harness runs through the door jamb and into the vehicle's interior. | Short to Battery: The most common cause. A wire within the harness has rubbed against a metal part of the vehicle, creating a direct connection to the battery voltage (usually a 12V wire). Insulation Damage: Cracked, frayed, or melted insulation can expose the wire and cause a short. Connector Issues: Loose, corroded, or damaged connectors can lead to intermittent or constant shorts. Wire Breakage: A broken wire can sometimes ground to the chassis or short to another wire. | |||
| Body Control Module (BCM) | The BCM is an electronic control unit that manages various vehicle functions, including the door ajar warning system. | Internal Failure (Rare): While less common, an internal short within the BCM itself can cause the B1573 code. This is usually diagnosed after ruling out other potential causes. Software Glitch (Very Rare): In extremely rare cases, a software glitch in the BCM could misinterpret the door ajar signal. A BCM reflash might be required. | |||
| Ground Connection | The door ajar circuit relies on a good ground connection for proper operation. | * Corrosion or Looseness: A corroded or loose ground connection can cause erratic readings and potentially trigger a short to voltage condition. Check ground points near the left rear door and the BCM. |
Detailed Explanations:
1. Door Ajar Switch (Left Rear):
The door ajar switch is a simple component, but its proper function is critical for the door ajar warning system. When the door is closed, the switch is depressed, signaling to the BCM that the door is securely shut. When the door is open, the switch is released, sending a different signal to the BCM, which then activates the door ajar warning light. A faulty switch can send incorrect signals, leading to the B1573 code. Check for physical damage, corrosion, and proper operation using a multimeter.
2. Wiring Harness:
The wiring harness is the most likely culprit in a B1573 DTC. The constant opening and closing of the door can cause the wires within the harness to flex and rub against the vehicle's metal frame. This can eventually wear away the insulation, leading to a short to battery voltage. The area where the harness passes through the door jamb is a common location for this type of damage. Carefully inspect the wiring for any signs of damage, including cracked, frayed, or melted insulation. Use a multimeter to check for continuity and shorts to ground or battery voltage. Don't forget to inspect the connectors for corrosion or damage.
3. Body Control Module (BCM):
The BCM is the central control unit for many of the vehicle's electrical systems. It receives signals from various sensors, including the door ajar switches, and controls corresponding functions, such as the door ajar warning light. While an internal failure of the BCM is less common, it is still a possibility. If you suspect a BCM issue, consult a qualified technician for further diagnosis and repair. They may use specialized diagnostic tools to test the BCM's functionality.
4. Ground Connection:
A proper ground connection is essential for the door ajar circuit to function correctly. A corroded or loose ground can cause erratic readings, potentially mimicking a short to voltage condition. Locate the ground points near the left rear door and the BCM and ensure they are clean, tight, and free of corrosion. Use a wire brush to clean the ground terminals and apply dielectric grease to prevent future corrosion.
Frequently Asked Questions:
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What does the B1573 code mean? It means there's a short to battery voltage in the left rear door ajar circuit. This typically indicates a wiring issue.
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Can I drive my car with the B1573 code? Yes, you can typically drive the vehicle, but the door ajar light might stay on, and there's a risk of battery drain. It's best to get it fixed as soon as possible.
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How do I fix the B1573 code? The most common fix involves inspecting and repairing the wiring harness in the left rear door jamb for shorts to battery voltage. You may also need to replace the door ajar switch or, in rare cases, the BCM.
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How much does it cost to fix the B1573 code? The cost can vary depending on the cause of the short. Wiring repairs are typically less expensive than replacing the BCM. Expect to pay anywhere from $100 to $500 or more.
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Can a bad door ajar switch drain my battery? Yes, if the switch is shorted to battery voltage, it can continuously draw power and drain the battery. This is especially true if the BCM is constantly trying to illuminate the interior lights or other accessories related to the door ajar system.
Troubleshooting Steps:
- Visual Inspection: Begin by visually inspecting the wiring harness in the left rear door jamb. Look for any signs of damage, such as cracked, frayed, or melted insulation. Pay close attention to the area where the harness passes through the door jamb.
- Multimeter Testing: Use a multimeter to test the continuity and voltage of the wires in the door ajar circuit. Disconnect the door ajar switch and check for a short to battery voltage on the wire connected to the BCM. Also, check for continuity between the wire and ground.
- Door Ajar Switch Testing: Test the door ajar switch itself using a multimeter. Ensure that the switch makes proper contact when the door is closed and that there is no continuity between the terminals when the door is open.
- Connector Inspection: Inspect the connectors associated with the door ajar switch and the BCM. Look for corrosion, loose terminals, or damaged connectors. Clean or replace any damaged connectors.
- BCM Diagnosis: If you suspect a BCM issue, consult a qualified technician for further diagnosis. They may use specialized diagnostic tools to test the BCM's functionality.
Tools Required:
- OBD-II Scanner: To retrieve the B1573 DTC.
- Multimeter: To test for continuity, voltage, and shorts.
- Wiring Diagram: For your specific vehicle model. This will help you identify the correct wires in the door ajar circuit.
- Wire Strippers/Crimpers: To repair damaged wiring.
- Electrical Tape or Heat Shrink Tubing: To insulate repaired wiring.
- Screwdrivers: To remove trim panels and access the door ajar switch and wiring harness.
- Socket Set: To remove ground connections.
- Wire Brush: To clean corroded terminals.
- Dielectric Grease: To prevent future corrosion.
Specific Vehicle Considerations (Toyota Example):
While the general principles of diagnosing and repairing a B1573 code are the same across different vehicle makes and models, there may be specific considerations for certain brands. For example, on some Toyota models, the door ajar switches are integrated into the door latch assembly. This means that replacing the entire door latch assembly may be necessary if the switch is faulty. Always consult the vehicle's service manual for specific instructions and wiring diagrams.
Preventative Measures:
- Regularly inspect the wiring harness in the door jambs: Look for any signs of wear or damage.
- Apply dielectric grease to electrical connectors: This will help prevent corrosion.
- Avoid slamming the doors: This can put stress on the wiring harness.
Conclusion:
The B1573 code indicates a short to battery voltage in the left rear door ajar circuit, most commonly caused by damaged wiring. Thorough inspection and repair of the wiring harness are usually necessary to resolve this issue. Consult a qualified technician if you are not comfortable performing electrical repairs.