Introduction
The B1393 diagnostic trouble code (DTC) indicates a problem within the power door memory lock relay circuit. This relay is crucial for the proper functioning of the memory feature associated with power door locks, allowing the vehicle to recall and automatically set the door locks to a pre-programmed position based on driver profiles or preferences. When the PCM (Powertrain Control Module) or BCM (Body Control Module) detects an open circuit in this relay's control circuit, it triggers the B1393 code, potentially disabling the memory lock function.
B1393 Code: Quick Reference Table
| Category | Description | Possible Causes |
|---|---|---|
| Definition | Power Door Memory Lock Relay Circuit Open | Open circuit in the relay control circuit, faulty power door memory lock relay, wiring harness issues (corrosion, damage, loose connections), BCM/PCM malfunction (rare), blown fuse (less common, but possible if the relay circuit is independently fused). |
| Symptoms | Power door memory lock feature not working, inability to program or recall door lock settings, intermittent door lock operation, security system malfunction (in some cases), "Check Engine" light or other warning lights illuminated. | Intermittent door lock operation, inability to save or recall door lock settings, no response from door lock memory functions, security system issues (if integrated with the door lock system), warning lights. |
| Troubleshooting Steps | Visually inspect wiring and connectors, check the power door memory lock relay, test circuit continuity, check for voltage at the relay, scan for other DTCs, inspect the BCM/PCM (as a last resort), verify fuse integrity, check ground connections. | Visual inspection of wiring and connectors, relay testing, continuity testing of the circuit, voltage checks, diagnostic scan for other codes, BCM/PCM inspection, fuse verification, ground connection check. |
Detailed Explanations
1. Power Door Memory Lock Relay Circuit Open: This refers to a break or interruption in the electrical circuit that controls the power door memory lock relay. An "open circuit" means that the electrical path is incomplete, preventing current from flowing to the relay and activating it.
2. Power Door Memory Lock Relay: This is an electromechanical switch that controls the power supply to the door lock actuators based on the memory settings. When the relay is activated, it allows power to flow to the door lock motors, enabling them to move to the pre-programmed positions. The relay is typically controlled by the BCM (Body Control Module) or PCM (Powertrain Control Module) based on input from the driver's seat memory settings and other related systems.
3. Open Circuit in the Relay Control Circuit: This is the most likely cause of the B1393 code. It could be due to a broken wire, a corroded connector, or a loose connection in the wiring harness that connects the BCM/PCM to the power door memory lock relay. Finding the exact location of the open circuit can require careful inspection and testing with a multimeter.
4. Faulty Power Door Memory Lock Relay: The relay itself could be defective. The internal contacts within the relay may be worn or damaged, preventing it from switching properly. Testing the relay with a multimeter or a relay tester can help determine if it is functioning correctly. You can also often swap it with an identical relay from a less critical system (like the rear window defogger relay) to see if the problem moves.
5. Wiring Harness Issues (Corrosion, Damage, Loose Connections): The wiring harness that contains the wires for the power door memory lock relay circuit can be susceptible to damage from environmental factors, such as moisture, heat, and vibration. Corrosion can build up on the connectors, creating a high-resistance connection or an open circuit. Physical damage to the wires, such as cuts or abrasions, can also cause an open circuit. Loose connections can occur at the relay connector, the BCM/PCM connector, or at any other connection point in the circuit.
6. BCM/PCM Malfunction (Rare): While less common, a malfunctioning BCM or PCM can also cause the B1393 code. The BCM/PCM is responsible for controlling the power door memory lock relay based on input from the driver's seat memory settings and other related systems. If the BCM/PCM is not sending the correct signal to the relay, it can cause the code to be set. This should be considered only after ruling out all other possible causes.
7. Blown Fuse (Less Common): Although less frequent, a blown fuse protecting the power door memory lock relay circuit can trigger the B1393 code. Some vehicles have independent fuses for specific door lock functions. Always check the fuse box diagrams to identify the correct fuse.
8. Power Door Memory Lock Feature Not Working: This is the most obvious symptom of the B1393 code. The power door memory lock feature will not function as intended. The driver may be unable to program or recall door lock settings.
9. Inability to Program or Recall Door Lock Settings: The driver will be unable to save their preferred door lock settings or recall previously saved settings. The memory function will be completely inoperative.
10. Intermittent Door Lock Operation: In some cases, the door locks may operate intermittently. This could be due to a loose connection or a corroded connector that is making intermittent contact.
11. Security System Malfunction (in some cases): If the door lock system is integrated with the vehicle's security system, a malfunction in the door lock system can sometimes trigger a security system malfunction. This is more likely if the security system relies on the door lock status for arming or disarming.
12. "Check Engine" Light or Other Warning Lights Illuminated: The B1393 code may trigger the "Check Engine" light or other warning lights on the instrument panel. This is a general indication that there is a problem with the vehicle's electrical system.
13. Visually Inspect Wiring and Connectors: The first step in troubleshooting the B1393 code is to visually inspect the wiring and connectors associated with the power door memory lock relay circuit. Look for any signs of damage, such as cuts, abrasions, or corrosion. Pay close attention to the connectors at the relay, the BCM/PCM, and any other connection points in the circuit.
14. Check the Power Door Memory Lock Relay: The relay can be tested using a multimeter or a relay tester. A multimeter can be used to check the resistance of the relay coil and the continuity of the relay contacts. A relay tester can automatically test the relay and indicate whether it is functioning correctly. You can also swap the relay with a known-good relay from a less critical system to see if the problem resolves.
15. Test Circuit Continuity: Use a multimeter to test the continuity of the wiring harness that connects the BCM/PCM to the power door memory lock relay. This will help to identify any open circuits in the wiring.
16. Check for Voltage at the Relay: Use a multimeter to check for voltage at the power door memory lock relay. This will help to determine if the relay is receiving power from the BCM/PCM.
17. Scan for Other DTCs: Use a scan tool to scan for other DTCs that may be related to the B1393 code. Other codes may provide clues as to the root cause of the problem.
18. Inspect the BCM/PCM (as a last resort): If all other possible causes have been ruled out, the BCM/PCM may need to be inspected. This should be done by a qualified technician, as it requires specialized knowledge and equipment.
19. Verify Fuse Integrity: Locate the fuse associated with the power door lock system and verify its integrity. A blown fuse will prevent power from reaching the relay.
20. Check Ground Connections: Ensure all ground connections associated with the door lock system and BCM/PCM are clean, tight, and free of corrosion. Poor ground connections can cause a variety of electrical problems.
Frequently Asked Questions
Q: What does the B1393 code mean? A: The B1393 code indicates an open circuit in the power door memory lock relay circuit, preventing the memory door lock feature from functioning correctly.
Q: What are the symptoms of a B1393 code? A: Common symptoms include the power door memory lock feature not working, inability to program or recall door lock settings, and possibly a "Check Engine" light.
Q: Can I fix the B1393 code myself? A: Depending on your mechanical skills, you may be able to diagnose and repair the issue by checking wiring, connectors, and the relay itself. However, more complex repairs may require a professional technician.
Q: How do I test the power door memory lock relay? A: You can test the relay with a multimeter to check its resistance and continuity or with a dedicated relay tester.
Q: Is the B1393 code serious? A: While it doesn't typically affect the vehicle's drivability, the B1393 code indicates a malfunction in the door lock memory system, which could be an inconvenience and potentially a security concern.
Conclusion
The B1393 code signifies an open circuit within the power door memory lock relay circuit, leading to a non-functional memory door lock system. Careful inspection of wiring, connectors, and the relay itself, along with thorough testing, are crucial for accurate diagnosis and effective repair.