B1339

What Does Code B1339 Mean?

The diagnostic trouble code B1339 signifies a “Chime Input Request Circuit Short To Battery.” This code is typically set by the Body Control Module (BCM), Instrument Cluster Module (ICM), or another module responsible for monitoring body electrical systems and driver warnings. It indicates that the control module has detected an abnormally high voltage, specifically battery voltage (approximately 12V or higher), on a circuit designated to signal a request for an audible chime. This circuit is designed to transition from a low voltage or ground state to a higher voltage (or vice versa, depending on the circuit design, but not full battery voltage) only under specific conditions, such as a seatbelt being unbuckled, a door being ajar, or a key left in the ignition. A “Short To Battery” implies that the signal wire for this chime request circuit has inadvertently made contact with a constant or switched 12V power source somewhere in the vehicle’s electrical system, providing a false input to the control module. This condition prevents the module from correctly interpreting the true state of the input, potentially causing the chime to activate erroneously, remain silent when it should be active, or trigger other system malfunctions.

Common Symptoms

• Constant Chime Activation: The most common symptom is an audible chime (e.g., seatbelt, door ajar, key-in-ignition) sounding continuously or intermittently, even when the conditions that should trigger it are not met.
• Absence of Chime: In some scenarios, if the short is severe or the module enters a fault-prevention mode, the chime might fail to activate when it should (e.g., no seatbelt chime when unbuckled).
• Erratic Instrument Cluster Behavior: Other warning lights or display messages on the instrument cluster may appear erratically if the short affects a shared communication line or power supply.
• Battery Drain: In rare cases, if the short is drawing significant current when the vehicle is off, it could lead to a parasitic battery drain.
• “Service Engine Soon” or Warning Light: While B-codes do not typically illuminate the Malfunction Indicator Lamp (MIL) directly, a specific body system warning light or a generic “Service Engine Soon” message might appear depending on the vehicle manufacturer’s strategy.

What Causes the Code B1339?

• Damaged Wiring Harness: The primary cause is physical damage to the wiring harness where the “Chime Input Request Circuit” wire has chafed, been pinched, or cut, allowing it to make contact with a live 12V power wire or a grounded metal component that is at battery potential. This can occur due to abrasion against sharp edges, inadequate routing, or rodent damage.
• Faulty Input Switch/Sensor: An internal electrical short within the switch or sensor that generates the chime request signal (e.g., seatbelt buckle switch, door jamb switch, ignition cylinder switch). The switch may have failed in a manner that shorts its output directly to its internal power supply or a nearby power wire.
• Corroded or Damaged Connectors: Corrosion, bent pins, or physical damage within a multi-pin electrical connector can bridge the chime input wire to an adjacent 12V power pin, creating the short to battery condition.
• Internal Control Module Fault: Although less common, an internal short or component failure within the BCM, ICM, or associated control module could cause it to falsely detect battery voltage on the chime input circuit, or an internal short within the module itself could be presenting battery voltage onto the circuit.

How to Diagnose and Troubleshoot

Diagnosing B1339 requires a systematic approach, often utilizing a digital multimeter (DMM), vehicle wiring diagrams, and an OBD-II scanner capable of reading B-codes and live data for body control modules.

1. Retrieve and Document Codes: Connect an OBD-II scanner and retrieve all active, pending, and historical Diagnostic Trouble Codes (DTCs) from all accessible modules, especially the BCM/ICM. Document the freeze frame data if available, as it can provide clues about the conditions present when the code was set.
2. Visual Inspection of Wiring and Connectors:
   • Begin with a thorough visual inspection of the wiring harness associated with the chime input request circuit. Consult vehicle-specific wiring diagrams to identify the exact wire, its color, and all connectors it passes through, from the input switch/sensor to the control module.
   • Focus on areas prone to damage: under the dashboard, door jambs (for door switches), under seats (for seatbelt switches), steering column (for ignition switches), and areas where harnesses pass through bulkheads or body panels. Look for signs of chafing, pinching, rubbing, corrosion, cuts, or rodent damage.
   • Inspect all relevant multi-pin connectors for bent pins, corrosion, loose terminals, or poor seating.
3. Isolate the Circuit – Initial Voltage Check:
   • With the ignition OFF, disconnect the electrical connector from the input switch/sensor (e.g., seatbelt buckle switch).
   • With the ignition ON (Key On Engine Off – KOEO), use a DMM to measure the voltage at the signal wire terminal of the disconnected switch connector (the wire that leads back to the control module). If battery voltage (approximately 12V) is present, the short to battery is in the wiring harness between this connector and the control module, or potentially at the module itself.
   • If no battery voltage is present at the switch connector, the short might be internal to the switch itself or further down the line when the switch is connected.
4. Test for Short to Battery in Wiring:
   • If the previous step indicated a short in the wiring, disconnect the main connector at the control module (BCM/ICM) that contains the chime input request circuit.
   • Using the wiring diagram, identify the specific pin for the chime input request circuit on the harness side of the disconnected control module connector.
   • With the ignition OFF, measure the resistance between this specific pin and a known good chassis ground. There should be infinite resistance (open circuit).
   • Then, measure resistance between this specific pin and the vehicle’s 12V battery positive terminal (or any constant 12V source on the vehicle). There should be infinite resistance. If low resistance or continuity is found to battery positive, the short is confirmed in the wiring harness.
   • To pinpoint the exact location of the short, systematically disconnect intermediate connectors along the chime input circuit path and re-test for the short until the problematic section of the harness is isolated.
5. Test the Input Switch/Sensor:
   • If the wiring harness tested clear of any short to battery, the fault may lie within the input switch or sensor itself.
   • With the switch disconnected, use a DMM to test its operation. Depending on the switch type, measure continuity or resistance across its terminals while actuating it (e.g., buckling/unbuckling a seatbelt, opening/closing a door). Verify that the switch opens and closes the circuit correctly and does not show an internal short to its power input or output when it shouldn’t. Refer to manufacturer specifications for expected resistance or voltage values.
6. Control Module Verification: If all wiring and switch components test good, and the short to battery persists at the module’s input pin even with the harness disconnected from the module, it strongly suggests a rare internal fault within the BCM/ICM. This would require further specialized diagnosis or module replacement.

Recommended Repairs and Solutions

• Repair or Replace Damaged Wiring: Once the specific section of the wiring harness causing the short is identified, the most effective solution is to carefully repair the damaged wires. This involves cutting out the compromised wire segment and splicing in a new, appropriately gauged wire using heat-shrink butt connectors for a durable, weather-resistant repair. Ensure that the repaired harness is routed correctly and secured to prevent future damage. If the damage is extensive or in a high-flex area, replacing the entire sub-harness may be a more reliable long-term solution.
• Replace Faulty Input Switch/Sensor: If diagnostic steps confirm an internal short within the input switch (e.g., seatbelt buckle sensor, door ajar switch, ignition key sensor), replace the faulty component. Use OEM quality parts to ensure proper functionality and integration with the vehicle’s systems.
• Clean or Replace Corroded Connectors: If corrosion is found bridging terminals within a connector, carefully clean the terminals using an electrical contact cleaner and a suitable brush. If terminals are severely corroded, bent, or damaged beyond repair, the connector housing and/or individual terminals should be replaced. After cleaning or replacement, apply dielectric grease to the connection to inhibit future corrosion.
• Inspect for Secondary Damage: After repairing the short, it is good practice to inspect any adjacent wiring harnesses, components, or fuses that may have been affected or damaged by the electrical short.
• Clear DTCs and Verify Repair: After completing the repairs, use an OBD-II scanner to clear the B1339 code from the control module’s memory. Perform several drive cycles and operate the vehicle under various conditions (e.g., open/close doors, buckle/unbuckle seatbelt) to confirm that the chime system functions correctly and that the code does not return. Monitor live data for the chime input circuit if available, to ensure stable voltage readings.