B1404

What Does Code B1404 Mean?

DTC B1404 indicates an open circuit condition detected within the control pathway for the driver’s side front power window “down” operation. While historically powertrain control modules (PCM/ECM) were the central diagnostic unit, modern vehicles often utilize a dedicated Body Control Module (BCM), a Door Control Module (DCM), or a similar integrated system controller to manage power window functionality. This code is set when the controlling module (e.g., BCM/DCM) attempts to command the driver’s power window to move downward, but it fails to detect the expected current flow or voltage drop across the associated motor circuit, or detects an abnormally high resistance/infinite resistance in the “down” circuit. Essentially, the module identifies a discontinuity preventing electrical power from reaching the window motor to actuate it in the downward direction, or from completing the circuit path.

Common Symptoms

• Driver’s Power Window Inoperative (Down Function Only): The most direct symptom is the inability to lower the driver’s side window using the primary or passenger switches. The ‘up’ function may or may not still operate, depending on the exact location of the open circuit.
• Driver’s Power Window Inoperative (Both Directions): If the open circuit affects a common power or ground supply to the motor, or a critical part of the motor itself, neither the ‘up’ nor ‘down’ function will work.
• No Click or Movement from Window Motor: When attempting to operate the window, there will be no audible click from relays (if applicable) or motor engagement, and no physical movement of the glass.
• Illuminated Malfunction Indicator Lamp (MIL) or Service Engine Soon Light: Although a body code, some manufacturers may trigger a dashboard warning for critical body system failures, especially if integrated with other safety or comfort systems.

What Causes the Code B1404?

• Damaged or Broken Wiring: The wiring harness supplying power, ground, or control signals to the driver’s window motor or switch can become chafed, pinched, or completely severed, particularly where it passes through the door jamb (A-pillar conduit).
• Corroded or Loose Electrical Connectors: Corrosion on terminals within the window motor connector, window switch connector, or door module connector can create an open circuit. Loose pins within these connectors can also interrupt the electrical path.
• Faulty Driver’s Power Window Motor: An internal open circuit within the window motor itself, such as a broken winding or brush, would prevent downward operation even with proper power and ground supplied externally.
• Defective Driver’s Power Window Switch: The internal contacts for the ‘down’ function within the master power window switch or the individual driver’s door switch can fail open, preventing the command signal from reaching the module or motor.
• Faulty Window Regulator Assembly (Integrated Motor): In some designs, the motor is an integral part of the regulator. A mechanical binding or internal failure within the regulator could cause an electrical open in the motor circuit due to excessive current draw or stress, leading to a subsequent thermal cutout or internal motor damage.
• Blown Fuse or Circuit Breaker: While less common for an “open circuit” specific to one direction (more common for a short circuit), a fuse related to a common power feed to the motor or module could have blown, resulting in an effective open.
• Failed Body Control Module (BCM) or Door Control Module (DCM): Internal failure within the module responsible for controlling the driver’s window, such as a burnt-out driver circuit for the ‘down’ function, could register as an open.

How to Diagnose and Troubleshoot

Diagnosing B1404 requires a methodical approach, utilizing a digital multimeter (DMM) and relevant wiring diagrams for the specific vehicle make and model.

1. Verify the Complaint and Retrieve Freeze Frame Data: Connect an OBD-II scanner to confirm B1404 is present. Review freeze frame data to understand operating conditions when the code was set. Clear the code and attempt to operate the window to see if the code immediately returns.
2. Visual Inspection of Wiring and Connectors: Carefully inspect the wiring harness running from the BCM/DCM to the driver’s door, specifically where it passes through the door jamb conduit. Check for any visible signs of chafing, pinching, cuts, or corrosion. Disconnect and inspect all relevant connectors (window switch, motor, door module) for bent pins, corrosion, or loose terminals.
3. Check Fuses: Consult the vehicle’s fuse diagram and inspect all fuses related to the power windows, BCM/DCM, and door modules. Use a DMM to check for continuity across each fuse.
4. Access the Window Motor Connector: Remove the door panel to gain access to the driver’s window motor connector.
5. Test Power and Ground at the Motor Connector:
   • With the ignition on and the window switch pressed to the ‘down’ position, use a DMM to back-probe the motor connector. Check for battery voltage (typically 12V) on the designated power wire(s) and a good ground connection on the ground wire(s). Refer to the wiring diagram to identify the correct pins. An absence of voltage or presence of resistance greater than 5 ohms on the ground path indicates an open upstream.
   • Note: Many power window systems are ‘reversing polarity’ systems, where the module or switch reverses polarity to change motor direction. In such cases, one wire will be 12V and the other ground for ‘down’ operation, and vice-versa for ‘up’ operation.
6. Test Window Switch Functionality: If power and ground are present at the motor connector when commanded, the issue likely lies within the motor itself or the circuit supplying power through the switch. If no power or ground is detected at the motor connector, the problem is upstream (switch, wiring, or module).
   • Disconnect the driver’s window switch. Using the wiring diagram, identify the power input, ground, and output wires for the ‘down’ function.
   • Test for power and ground at the switch connector.
   • Using a DMM in continuity mode or resistance mode, test the switch itself. With the switch disconnected, actuate the ‘down’ position and check for continuity between the input power pin and the output pin for the ‘down’ circuit. An open indicates a faulty switch.
7. Test Window Motor Continuity/Resistance: With the window motor connector disconnected, measure the resistance across the motor’s power and ground terminals. A typical power window motor will have a resistance in the low single-digit ohms range (e.g., 0.5-5 ohms). An infinite resistance reading indicates an internal open circuit within the motor.
8. Test Wiring Continuity: If the motor and switch test good, the open circuit is within the wiring itself. Disconnect both ends of the suspect wires (e.g., between the switch and the motor, or between the BCM/DCM and the switch/motor). Use a DMM to check for continuity. Wiggle the harness while testing to identify intermittent opens.
9. Inspect for Water Intrusion: Check for signs of water intrusion in the door cavity or near control modules, which can lead to corrosion and open circuits.

Recommended Repairs and Solutions

The repair for B1404 depends on the root cause identified during diagnosis. Always ensure the battery is disconnected before performing electrical repairs.

• Repair Damaged Wiring: If damaged wiring is found, perform a professional wire repair using soldering and heat-shrink tubing for durability and moisture resistance. Avoid using crimp connectors in high-flex areas like the door jamb. Replace severely damaged sections of the harness if necessary.
• Clean or Replace Corroded Connectors: For corroded terminals, use electrical contact cleaner and a small brush to remove corrosion. If corrosion is severe or pins are bent/loose, the connector body or individual terminals should be replaced. Apply dielectric grease to new connections to prevent future corrosion.
• Replace Faulty Driver’s Power Window Motor: If the motor tests open or shows signs of internal failure, replace the entire window motor assembly. In many cases, the motor is integrated with the window regulator and must be replaced as a unit. Ensure proper alignment and lubrication during installation.
• Replace Defective Driver’s Power Window Switch: If the switch fails continuity tests for the ‘down’ function, replace the switch unit. Use an OEM or high-quality aftermarket replacement for optimal performance and fitment.
• Replace Blown Fuses: If a blown fuse is found, replace it with a fuse of the correct amperage. However, investigate why the fuse blew, as a short circuit elsewhere could be the underlying cause, not an open circuit.
• Replace Faulty BCM/DCM: If all other components and wiring test good, and module output tests (if available via advanced scanner) confirm the module is not providing the ‘down’ command, the BCM or DCM may need replacement. Note that module replacement often requires programming or configuration using specialized diagnostic tools.
• After Repair: After any repair, clear the DTC B1404, perform a power window initialization/relearn procedure (if required by the manufacturer), and thoroughly test the window’s operation in both directions multiple times to ensure the repair is successful and the code does not return.