B1337

What Does Code B1337 Mean?

DTC B1337 signifies a diagnostic condition indicating a Rear Right Door Ajar Switch Circuit Short To Battery. This code is typically set by the Body Control Module (BCM) or General Module (GM), which is responsible for monitoring various body electrical systems, including door status. The BCM/GM continuously monitors the voltage potential on the circuit dedicated to the rear right door ajar switch. Under normal operation, this circuit’s voltage should fluctuate between a low state (near ground, indicating the door is closed) and a reference voltage or open circuit state (indicating the door is ajar). When the BCM/GM detects a sustained voltage level on this circuit that is consistent with the vehicle’s battery voltage (e.g., 12-14 volts), irrespective of the actual door position, it interprets this as an electrical short to a constant power source (battery voltage) within the circuit. This anomaly triggers the B1337 diagnostic trouble code, indicating an erroneous signal that the rear right door is constantly “open” or “ajar” due to an electrical malfunction rather than its physical state.

Common Symptoms

• Constant Rear Right Door Ajar Warning Light: The most direct and common symptom is the illumination of the rear right door ajar warning indicator on the instrument cluster, even when the door is securely closed.
• Interior Dome Light Malfunction: Interior lights (dome light, courtesy lights) may remain continuously illuminated or fail to operate correctly, as the system perceives an open door. This can lead to significant battery drain if left unattended.
• Central Locking System Irregularities: The central locking system may fail to arm fully, or the rear right door may not lock/unlock properly via remote or interior controls, as the system interprets it as already open.
• Security Alarm System Issues: The vehicle’s security system may be prevented from arming, or false alarms may occur due to the perceived open door condition.
• Power Window Inoperability: In some sophisticated body control systems, power window operation for the affected door might be temporarily disabled as a safety or system integrity measure.

What Causes the Code B1337?

• Damaged Wiring Harness: The most frequent cause involves physical damage to the wiring harness leading to the rear right door ajar switch. This can include chafing, pinching, or cutting of the signal wire, causing it to contact a live 12-volt power wire within the door jamb, door panel, or vehicle chassis.
• Corroded Electrical Connectors: Water intrusion or high humidity can lead to corrosion within the electrical connectors associated with the rear right door ajar circuit. This corrosion can create a conductive path, effectively bridging the signal wire to a power supply within the connector itself.
• Faulty Rear Right Door Ajar Switch: While less common for a “short to battery” condition compared to a stuck open/closed fault, an internal short within the door ajar switch itself could cause the signal circuit to be continuously supplied with battery voltage.
• Internal Body Control Module (BCM) or General Module (GM) Fault: In rare instances, an internal malfunction or short within the BCM/GM’s input circuit for the rear right door ajar switch could incorrectly interpret or supply battery voltage to the signal line. This is typically a last-resort diagnosis after all external wiring and component checks are exhaustive.

How to Diagnose and Troubleshoot

Diagnosis of DTC B1337 requires a systematic approach using appropriate diagnostic tools and electrical testing procedures:

1. Visual Inspection: Begin with a thorough visual examination. Inspect the rear right door jamb and the flexible rubber boot connecting the door to the body for any signs of wiring damage, such as pinching, fraying, or cuts. Check for corrosion or loose connections at the door ajar switch itself and at any visible inline connectors for the door harness.
2. OBD-II Scanner Live Data Analysis: Connect an advanced OBD-II scanner capable of communicating with the BCM/GM. Navigate to the live data stream for the body control module and monitor the parameter indicating the status of the “Rear Right Door Ajar.” Even with the door securely closed, if the code is present, the scanner will likely display an “open” or “ajar” status, confirming the module is receiving an erroneous signal.
3. Digital Multimeter (DMM) Voltage and Continuity Testing:
   • Isolate the Circuit: Disconnect the electrical connector from the rear right door ajar switch. This isolates the switch from the wiring harness.
   • Check for Short to Battery (Harness Side): With the door ajar switch disconnected and the vehicle ignition on, use a DMM to measure the voltage between the signal wire terminal (consult the vehicle’s specific wiring diagram for the correct pinout) on the wiring harness side of the connector and a known good chassis ground. A reading of approximately battery voltage (e.g., 12-14V) at this point definitively indicates a short to battery within the wiring harness between the connector and the BCM/GM.
   • Inspect Switch Functionality (If Necessary): If no short to battery is found on the harness side, test the door ajar switch itself. Depending on the switch type (e.g., simple contact, Hall effect), consult the service manual for the proper testing procedure. For a simple contact switch, test for continuity in both open and closed positions; it should not show continuity to battery voltage.
   • Continuity Test to BCM/GM: If the short is not present at the switch connector, trace the signal wire further. Disconnect the appropriate connector at the BCM/GM. Perform a continuity test on the signal wire from the rear right door ajar switch connector (harness side) to the corresponding pin at the BCM/GM connector (harness side) to ensure wire integrity. Additionally, perform a continuity test from the signal wire to all other power wires and chassis ground within the harness to precisely locate the short.
4. Wiring Diagram Analysis: Always refer to the specific vehicle’s wiring diagrams for accurate pin assignments, wire colors, and component locations. This is crucial for precise testing.

Recommended Repairs and Solutions

Once the source of the B1337 code has been accurately diagnosed, the following repairs are typically performed:

• Repair or Replace Damaged Wiring Harness: This is the most common resolution. Carefully locate the section of the rear right door ajar switch wiring that has shorted to a power source. Repair the damaged wire by soldering in a new section, ensuring proper insulation with heat-shrink tubing. Reroute the wiring to prevent future damage, especially within the door jamb boot where wires are prone to flexing and wear. If the damage is extensive or involves multiple conductors, replacing the entire affected segment of the wiring harness may be more practical and reliable.
• Replace Rear Right Door Ajar Switch: If diagnostic testing conclusively points to an internal fault or short within the door ajar switch itself, replace the switch with a new OEM-quality component. Ensure correct installation and verify proper operation after replacement.
• Clean or Replace Corroded Connectors: If corrosion is identified within any connectors along the circuit, disconnect them and thoroughly clean the pins using an appropriate electrical contact cleaner and a small brush. Inspect the terminals for damage or excessive wear and repair or replace them as needed. Apply dielectric grease upon reassembly to prevent future corrosion.
• Body Control Module (BCM) / General Module (GM) Replacement: Only consider replacing the BCM/GM as a last resort, after all other external wiring, connectors, and the door ajar switch have been thoroughly tested and confirmed to be in good working order. BCM/GM replacement is often expensive and typically requires specialized programming and calibration with a factory-level diagnostic tool after installation.