B1394

What Does Code B1394 Mean?

DTC B1394 signifies a detected electrical fault within the Power Door Memory Lock Relay Circuit, specifically indicating a Short To Battery. This diagnostic trouble code is typically registered by a Body Control Module (BCM) or a dedicated Door Control Module (DCM) rather than the powertrain control module (PCM/ECM). The BCM/DCM monitors the electrical characteristics of critical circuits, including those for vehicle access and security systems. When the module detects an unexpectedly high voltage condition on the power door memory lock relay’s control or load circuit – specifically, a voltage level approaching nominal battery voltage (approximately 12V) when the circuit should be inactive, at ground, or at a lower controlled voltage – it interprets this as a short to a constant power source. This condition can prevent the memory lock relay from operating correctly, impacting functions such as remote keyless entry, automatic door locking/unlocking, and user-defined lock behaviors by either constantly energizing the relay or sending an erroneous signal to the door lock actuators.

Common Symptoms

• Inoperative Power Door Locks: Doors may not lock or unlock via the remote key fob, interior door switches, or automatic functions.
• Intermittent or Spontaneous Locking/Unlocking: Doors may unexpectedly lock or unlock without user input.
• Battery Drain: If the short causes the relay to be constantly energized, it can lead to a parasitic drain on the vehicle’s battery over time.
• Loss of Memory Lock Functions: Custom lock settings or memory positions may not function as programmed.
• Audible Clicking: The power door memory lock relay may be heard clicking continuously or intermittently without any corresponding action.
• Warning Lights: Related security system, keyless entry, or general warning lights may illuminate on the instrument cluster.

What Causes the Code B1394?

• Damaged Wiring Harness: Chafed, pinched, or cut wiring within the power door memory lock relay circuit, leading to contact with a constant 12V power supply. Common areas include door jambs, under carpeting, or behind interior trim panels.
• Faulty Power Door Memory Lock Relay: An internal short within the relay itself, causing the control coil or contact terminals to be permanently connected to battery voltage.
• Malfunctioning Body Control Module (BCM) or Door Control Module (DCM): An internal fault or short within the control module that is responsible for commanding the relay, causing it to output constant battery voltage on the relay’s control circuit.
• Corroded or Damaged Connectors: Corrosion, bent pins, or foreign material within the relay socket or associated wiring connectors, bridging the circuit to a power source.
• Improper Aftermarket Accessory Installation: Incorrectly wired aftermarket alarms, remote starters, or other electronic accessories that tap into the door lock circuits, creating an unintended short to power.

How to Diagnose and Troubleshoot

Diagnosis of B1394 requires a systematic approach, often utilizing a digital multimeter (DMM) and vehicle-specific wiring diagrams.

1. Retrieve Freeze Frame Data: Connect an OBD-II scanner and retrieve any available freeze frame data associated with B1394. This data provides insights into the vehicle’s operating conditions (e.g., ignition status, battery voltage) when the fault was detected, which can aid in replication.
2. Visual Inspection: Perform a thorough visual inspection of the wiring harness for the power door memory lock relay circuit. Pay close attention to areas prone to movement or abrasion, such as door jambs, under seats, and behind dashboard components. Look for signs of chafing, pinching, corrosion, or modifications. Inspect the relay and its socket for obvious damage or corrosion.
3. Locate the Power Door Memory Lock Relay: Consult the vehicle’s service manual and wiring diagrams to precisely locate the power door memory lock relay and the controlling module (BCM/DCM). Understand the pinout and function of each terminal on the relay and its connector.
4. Test Relay Control Circuit Voltage:
   • With the ignition OFF and the relay disconnected from its socket, use a DMM to measure voltage between the relay’s control terminal (the one receiving the activation signal from the BCM/DCM) and a known good ground.
   • A reading of 0V is expected when the circuit is inactive. If the DMM reads near battery voltage (e.g., 12V), this confirms a short to battery on the control side of the circuit.
   • Also, identify and test the constant 12V feed to the relay’s load side. This circuit should always have battery voltage.
5. Test the Relay Itself:
   • Remove the power door memory lock relay from the vehicle.
   • Using a fused jumper wire, apply 12V and ground to the relay’s control coil terminals as per the wiring diagram. Listen for an audible “click,” indicating the coil is energizing.
   • Using the DMM in continuity mode, test for continuity across the relay’s switch terminals. Continuity should only be present when the coil is energized. If there is continuity at all times, the relay is internally shorted.
   • Measure the resistance of the relay coil. Compare this to specifications; an open circuit or extremely low resistance indicates a faulty coil.
6. Isolate the Short:
   • If the relay control circuit measured 12V with the relay disconnected (Step 4), disconnect the BCM/DCM connector that controls this circuit.
   • Re-measure voltage on the problematic wire at the relay socket. If the voltage now drops to 0V, the short is likely internal to the BCM/DCM.
   • If the voltage remains near 12V, the short is within the wiring harness between the BCM/DCM connector and the relay socket. Proceed to meticulously trace and inspect this section of the harness for damage.
7. Continuity and Resistance Checks: Perform continuity checks on suspect wires between components (BCM/DCM, relay, door lock actuators) to ensure intact circuits. Check for unintended continuity between the affected wire and a constant 12V source, or between the wire and ground, to pinpoint the short.

Recommended Repairs and Solutions

Once the root cause of DTC B1394 has been accurately identified through comprehensive diagnostics, the following repairs can be implemented:

• Repair or Replace Damaged Wiring: If the diagnostics indicate a short in the wiring harness, carefully locate the damaged section. If the damage is minor, repair it using appropriate gauge wire, solder connections, and heat-shrink tubing for insulation. Ensure the repair is robust and properly insulated from potential power sources. For extensive or inaccessible damage, replacing the entire sub-harness may be more practical. Route new wiring securely to prevent recurrence.
• Replace the Power Door Memory Lock Relay: If the relay itself is found to be internally shorted or otherwise faulty, replace it with a new OEM (Original Equipment Manufacturer) or equivalent quality aftermarket component. Ensure the new relay matches the specifications and part number of the original.
• Replace the Body Control Module (BCM) or Door Control Module (DCM): If the diagnostic steps point to an internal short or malfunction within the BCM or DCM, module replacement will be necessary. It is crucial to note that BCM/DCM replacement often requires specialized programming or configuration using a factory-level scan tool to integrate the new module with the vehicle’s immobilizer and other systems. Failure to do so can result in no-start conditions or additional electronic malfunctions.
• Clean and Repair Corroded Connectors: If corrosion is identified within the relay socket or other connectors, carefully clean the pins using an electrical contact cleaner and a small brush. Inspect for bent or splayed pins and correct them as necessary. After cleaning, apply a thin layer of dielectric grease to prevent future corrosion.
• Address Aftermarket Accessory Issues: If an aftermarket accessory is found to be causing the short, remove it or properly re-wire it according to best automotive electrical practices, ensuring all connections are secure, insulated, and fused appropriately.