B1423

What Does Code B1423 Mean?

DTC B1423, “Power Window RR Motor Circuit Open,” signifies that the vehicle’s control module, typically the Body Control Module (BCM) or a dedicated Door Control Module (DCM) – rather than the Engine Control Module (ECM) or Powertrain Control Module (PCM) – has detected an open circuit condition within the electrical system of the rear right (RR) power window motor. An open circuit implies a break in the electrical path, preventing current flow to the motor. The control module monitors the circuit for expected resistance, voltage, or current draw. When it attempts to command the rear right window motor to operate (up or down) and detects infinite resistance, no current flow, or an anomalous voltage signature where it anticipates an active circuit, it registers this diagnostic trouble code. This condition directly impacts the functionality of the rear right power window, rendering it inoperable as the motor cannot receive the necessary electrical energy to move the window regulator.

Common Symptoms

• The rear right power window is completely inoperable from both its individual door switch and the driver’s master control switch.
• The rear right window may be stuck in a specific position (up, down, or partially open).
• No audible click or motor whine when attempting to operate the rear right window.
• Other power windows function normally.

What Causes the Code B1423?

• Internal failure of the rear right power window motor: An open winding or internal disconnection within the motor itself is a common cause, leading to infinite resistance in the circuit.
• Damaged or broken wiring harness: A break, fraying, or complete severance in the power, ground, or control wires leading to the rear right window motor. This is frequently observed in the door jamb area due to repetitive flexing over time, or from impact/water intrusion.
• Faulty window switch (individual or master): An open contact or internal defect within the rear right door switch or the driver’s side master power window switch preventing proper power or the control signal from reaching the motor.
• Corroded or loose electrical connectors: High resistance or a complete open circuit at the connector points leading to or from the window motor, switch, or control module due to moisture intrusion, vibration, or poor contact.
• Blown fuse: A fuse protecting the rear right window motor circuit may have blown, effectively creating an open circuit to the motor.
• Failure of the Body Control Module (BCM) or Door Control Module (DCM): While less common, an internal failure in the specific driver or output circuit within the control module responsible for powering and controlling the rear right window motor can result in an open circuit.

How to Diagnose and Troubleshoot

A systematic approach using a digital multimeter (DMM) and relevant wiring diagrams is crucial for diagnosing B1423.

1. Retrieve and Document DTCs: Connect an OBD-II scanner to the vehicle’s DLC. Confirm B1423 is present and check for any related or accompanying body electrical codes. Document all codes and clear them to see if B1423 immediately returns or is an intermittent issue.
2. Visual Inspection:
   • Inspect the wiring harness where it passes from the body into the rear right door (the door jamb boot). Look for signs of chafing, pinching, or broken wires.
   • Remove the rear right door panel to gain access to the window motor, regulator, and switch. Visually inspect all connectors for corrosion, bent pins, or signs of looseness.
   • Check the window motor and regulator assembly for any physical damage or binding.
3. Check Fuses: Consult the vehicle’s service manual for the location of the fuse(s) protecting the rear right power window circuit. Use a DMM to check for continuity across the fuse, or visually inspect it. Replace any blown fuses and retest. Note that a repeatedly blown fuse indicates a short circuit elsewhere, which an “open circuit” code does not typically specify directly but can precede an open if the component fails after a short.
4. Test Power and Ground at Motor Connector:
   • With the rear right window motor connector unplugged, identify the power and ground wires using the wiring diagram.
   • With the ignition ON, use a DMM to check for battery voltage (B+) at the power wire terminal(s) when the individual rear right window switch and/or master switch are activated (for both up and down commands).
   • Check for a good ground connection at the motor’s ground wire terminal by measuring resistance to chassis ground (should be less than 0.5 ohms) or voltage drop with a load.
   • If no power or ground is present, trace the circuit back towards the switch or BCM/DCM.
5. Test Window Motor Resistance:
   • With the motor connector unplugged, measure the resistance across the motor’s power and ground terminals (or appropriate motor drive terminals as per wiring diagram).
   • An operating motor should show a low, measurable resistance (typically a few ohms to tens of ohms, varying by motor design). An “open circuit” motor will display infinite resistance (OL on most DMMs).
   • If the motor shows infinite resistance, it is internally failed.
6. Test Window Switches:
   • Use the wiring diagram to identify the input and output terminals of both the rear right door switch and the master control switch.
   • With the switches unplugged, use a DMM to check for continuity or resistance changes across the appropriate terminals when the switch is operated in both directions (up/down). Look for an open circuit condition within the switch itself.
   • Some modern systems use digital signals; in such cases, scanner live data for switch status would be more appropriate.
7. Continuity Test of Wiring Harness:
   • If power/ground is missing at the motor, or the switch tests good, perform continuity tests on the individual wires between the switch, motor, and the control module (BCM/DCM). Disconnect both ends of the suspect wire and measure resistance. A good wire should show very low resistance (less than 0.5 ohms). Infinite resistance indicates a break.
   • Pay particular attention to the wiring within the flexible door jamb boot.
8. Bypass Test (Caution Advised): As a final confirmation of a failed motor (and only if certain of power/ground connections), you can carefully apply fused battery voltage directly to the motor’s power and ground terminals using jumper wires with an inline fuse (e.g., 20A). If the motor does not operate, it confirms an internal motor failure. Ensure the window regulator is not binding during this test.

Recommended Repairs and Solutions

The repair for B1423 depends directly on the root cause identified during the diagnostic process:

• Repair or Replace Damaged Wiring: If a broken wire is identified, it should be repaired using proper automotive wiring techniques, including soldering and heat-shrink tubing for durability. For extensive damage or multiple broken wires in the door jamb, it may be more efficient and reliable to replace the entire section of the wiring harness.
• Replace the Rear Right Power Window Motor/Regulator Assembly: If diagnostic steps confirm an internal open circuit within the motor, the motor itself will need replacement. Often, the motor is sold as an integral part of the window regulator assembly. Ensure the new assembly is correctly installed and aligned to prevent binding.
• Replace Faulty Window Switch: If either the individual rear right door switch or the driver’s master control switch is found to have an internal open circuit, replace the respective switch assembly. Ensure the new switch is compatible with the vehicle’s electrical system, especially for modules with network communication.
• Clean Corroded Connectors: If corrosion is the issue, disconnect the battery, thoroughly clean the affected terminals using an electrical contact cleaner and a small brush. Apply a thin layer of dielectric grease to the cleaned terminals before reassembly to prevent future corrosion.
• Replace Blown Fuse: If a blown fuse was the cause, replace it with a fuse of the correct amperage. However, investigate why the fuse blew to prevent recurrence; a blown fuse often indicates a downstream short circuit that may need addressing.
• Replace Body Control Module (BCM) or Door Control Module (DCM): This should be a last resort after thoroughly ruling out all other possibilities. If the module is confirmed to have an internal failure preventing power or control signal delivery, it will need to be replaced. BCMs and DCMs often require programming or calibration by a dealership or a shop with specialized diagnostic tools after replacement.

Mechanics’ Tips:

• Always disconnect the vehicle’s battery before performing any electrical repairs to prevent accidental shorts or damage to control modules.
• When working with window regulators, be mindful of potential pinch points and the spring tension of the regulator. Secure the window glass in the up position before removing the motor or regulator.
• After replacing components, test all window functions (up/down, anti-pinch if equipped) from both the individual door switch and the master control switch.
• Clear all DTCs and perform a test drive or operate the window several times to ensure the code does not return.
• Always refer to the vehicle-specific service manual for detailed wiring diagrams, connector pin-outs, and component testing specifications. These resources are invaluable for accurate diagnosis.